Sierra Slope System Design Guide

Sierra Slope System Design Guide
®
Design Guidelines
Tensar Earth Technologies, Inc.
TABLE OF CONTENTS
1.0 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.0 SIERRA SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2
History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.1 Tensar Structural Geogrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Erosion Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3
Material Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.1 Tensar Structural Geogrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.2 Drainage Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3.3 Erosion Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4
System Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.5
System Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
1
1
1
2
2
2
3
3
3
3
3.0 SIERRA SLOPE DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1
Design Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3
Design Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3.1 Design Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.2 Total Stress vs. Effective Stress Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.3 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.4 Structural Geogrid Reinforcement Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3.5 Slope Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3.6 Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.3.6.1 Limit Equilibrium Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
3.3.6.2 Simplified Bishop Method of Slices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3.3.7 Safety Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3.8 Seismic Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4
Soil-Reinforcement Interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5
Internal Water Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.6
Surface Drainage & Erosion Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6.1 Surface Water Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6.2 Surficial Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6.3 Landscape Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.6.4 Erosion Control Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.6.5 Erosion Control Systems Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.0 SIERRA EXPERIENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
5.0 ADVANTAGES & DISADVANTAGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
5.1
Advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
5.2
Possible Disadvantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
6.0 TYPICAL COSTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.0 SPECIFICATION FOR MECHANICALLY STABILIZED EARTH RETENTION SYSTEM . . . .18
7.1
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.1.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.1.1.1 Related Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.1.1.2 Alternates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
7.1.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
7.1.3
7.1.4
7.1.5
7.1.6
7.2
7.2.1
7.2.2
7.2.2.1
7.2.2.2
7.2.2.3
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.3.6
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Submittals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Quality Assurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Delivery, Storage & Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Manufacturers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Structural Geogrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Geosynthetic Drainage Composite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Erosion Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Execution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Fill Placement Over the Geogrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
8.0 SIERRA INSTALLATION GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
9.0 MAINTENANCE & MOWING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
APPENDIX A - REINFORCED FILL SOIL PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
A.1 Gradation, Plasticity Index, and Chemical Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
A.2 Soil Fill Design Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
A.3 Topsoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
APPENDIX B - VEGETATION & EROSION CONTROL SYSTEM SELECTION GUIDELINES . .29
B.1 Vegetation Facing Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
B.2 Erosion Control System Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
FIGURES
Figure 1.1
Figure 2.1
Figure 2.2
Figure 3.1
Figure 3.2
Figure 6.1
Figure 8.1
Figure 8.2
Figure 8.3
Figure 8.4
Figure 8.5
Figure 8.6
Figure 8.7
Figure 8.8
Replacing Concrete Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Typical Section, Sierra Slope Retention System . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Processing Tensar Geogrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical Critical Failure Surfaces for an MSE Slope . . . . . . . . . . . . . . . . . . . . . . . . 6
Forces Acting on a Typical Slice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Sierra Cost Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Benching the Backcut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Types of Tensar Geogrid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Placing Geogrid Strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Placing Geogrid on Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Placing Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Compaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Burial of Transverse Terminal Ends (6 in. x 12 in.) . . . . . . . . . . . . . . . . . . . . . . . . .26
SierraScape System Detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
TABLES
Table B.1
Table B.2
Recommended Maximum Slope Angle & Typical Sites for Vegetation . . . . . . . .29
Erosion Control System Selection Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.0 INTRODUCTION
This submittal introduces the Sierra® Slope
Retention System to transportation agencies for
review and approval as an alternative earth
retention system. Provided herein is a discussion
of the history, structural components, design
methodologies, performance, experience, and case
studies that document that this system meets all
current standards for mechanically stabilized
earth (MSE) systems. The Sierra System is the
natural looking alternative to conventional or
precast MSE retaining wall systems (Figure 1.1).
systems set by transportation agencies. The Sierra
System is an MSE system that includes:
❿ Tensar Geogrid soil reinforcement
❿ Drainage Composite
❿ Erosion Control Systems
❿ Design and engineering
❿ On-site technical assistance
❿ Twenty years of technical expertise and
construction experience to handle any
site-specific detail, design question, or
construction issue
Throughout this manual, we will use the familiar
term Mechanically Stabilized Earth (MSE) to describe
multiple layers of reinforcement inclusions that
act as reinforcement within soil fill. FHWA
NHI-00-043, 2001 describes the form of MSE that
incorporates planar reinforcing elements in
constructed earth-slope structures with free
inclinations of less than 70°, as Reinforced Soil
Slopes (RSS).
2.2 History
The Tensar Corporation introduced synthetic
structural geogrids in North America and is the
recognized leader in geogrid soil reinforcement
technology. For over two decades, Tensar reinforced
soil slopes have provided a natural and economical
alternative to conventional MSE wall systems.
The Tensar Corporation offers far more installations
and experience than any other enterprise in
the industry.
Figure 1.1 — Replacing Concrete Retaining Walls
The Sierra Slope Retention System is a complete
reinforced soil slope system specifically developed
for public transportation applications. The system
consists of proven Tensar® Geogrids for soil
reinforcement, drainage composite for internal
drainage; an Erosion Control System by Tensar
Earth Technologies (TET) design based on local
soil types, climate, vegetation and slope angle; and
the expertise of TET for design and installation.
Through a combination of technologies, the
Sierra Slope Retention System provides reliable
performance backed by years of research and
experience on completed projects worldwide.
We request that the Sierra System be approved
for use and included as an alternative MSE
system for all grade separation requirements
including retaining walls on future agency projects.
2.0 SIERRA SYSTEM
2.1 Background
The Sierra System was developed specifically to
meet, or exceed, the high standards for MSE
2.2.1 Tensar Structural Geogrids
Tensar Geogrids were developed in the late 1970s by
Netlon Limited of Blackburn, England, specifically
for permanent reinforcement of soil and aggregate
materials. Principal applications are roadway
subgrade improvement and base reinforcement,
reinforced soil retaining walls, reinforced soil
slopes, and embankments constructed over soft
ground. The first installation of Tensar Geogrids
in the United States was a Tensar reinforced soil
slope in 1982 for the Texas State Department
of Transportation. Since then, thousands of
projects have been completed and are performing
successfully. There have been no known failures
of Tensar reinforced soil slopes due to failure of
the product or technology since its development.
Tensar Geogrids have been manufactured in
Morrow, Georgia since 1984.
1
2.2.2 Erosion Control Systems
The Tensar Corporation has been designing
erosion control systems for reinforced slopes since
the first installation in North America in 1982 for
the Ministry of Transportation - Ontario, Canada.
Effective vegetative erosion control systems combine
engineered products as well as horticultural
technologies. The experience of Tensar Earth
Technologies in the design and construction of
hundreds of Sierra Slopes, in a wide variety of
climates using several types of vegetative systems,
is unparalleled in the industry.
Structural geogrids are manufactured through a
series of precise steps. The result is a unique
material with specific performance capabilities
as a soil reinforcing element. Both the Tensar
manufacturing process and the Tensar product
are covered by U.S. patents.
A brief summary of the manufactured process has
been presented by Wrigley.
“A simplified depiction of the manufacturing
process is presented in Figure 2.2. Accurately
controlled polymer (typically HDPE or PP)
sheet is first punched with a precise pattern of
holes. This punched sheet is then drawn in the
machine, longitudinal direction under closely
controlled conditions at a temperature below
the melting point of the chosen polymer. This
produces either a ‘uniaxial’ geogrid or feed
stock for subsequent transverse drawing into a
‘biaxial’ geogrid. The form and performance
of these patented products is controlled by the
precision of the thickness and holes of the
‘punched’ sheet and the drawing conditions.
2.3 Material Components
Tensar Geogrids, drainage composites and erosion
control systems combine to form a safe, reliable,
and durable slope system that offers a very costeffective alternative to retaining walls. Figure 2.1
illustrates a typical Sierra Slope.
Uniform Surcharge = q
Erosion Control System
Slope Angle = β
Structural Geogrid Reinforcement
In the extruded sheet, the polymer is in the
form of essentially randomly arranged small
crystallites separated by thin amorphous
zones. Most molecules are sufficiently long to
pass through several crystallites thus linking
them together with strong molecular chains
(Wrigley2 ) . During drawing below melting
temperature the crystallites and the molecular
chains in the amorphous zones are aligned
(oriented) in the direction of draw. The
importance of this continuation of molecular
orientation into the junction zones on
load-bearing performance was recognized in
the product patents.”
Varies
1
Slope Height = H
Reinforced Slope Fill
Secondary (Surficial) Geogrid Reinforcement
Internal Drainage
Element
Random Backfill
Tensar Structural Geogrid (typ.)
Foundation Soil
Figure 2.1 — Typical Section, Sierra Slope Retention System
2.3.1 Tensar Structural Geogrids
Tensar Geogrids are made of select high density
polyethylene (HDPE) and polypropylene (PP)
to offer maximum long-term performance.
Tensar Geogrids are durable in the presence of
virtually every fill soil typically used in highway
construction and are inert to electro-chemical
corrosive attack.
Tensar Geogrid reinforcement consists of a regular
network of integrally connected longitudinal and
transverse polymer tensile elements. The open
aperture geometry is designed to create significant
mechanical interlock with surrounding soil,
aggregate, or other fill material. Because of this,
Tensar Geogrids can be used to effectively
reinforce most soils and are not limited to use in
select granular fill.
2
The Tensar Corporation operates a comprehensive
Quality Assurance (QA) program in its manufacturing plant3. Quality Control (QC) is independently
conducted by a separate department/laboratory.
Punched Sheet
Uniaxial
Geogrid
Polymer Sheet
Biaxial Geogrid
The typical erosion control system will employ
a biotechnical design using engineering technology
and horticultural experience that relies on a
combination of geosynthetic materials as well as
vegetation to create a stable and aesthetic slope
facing system. To address these issues and provide
a design that will function well under local
environmental conditions, Tensar has consulted
with landscape architects experienced in providing
local and regional designs for plant selection,
landscape design, and erosion control solutions for
the Sierra Slope Retention System. Sierra Slope
erosion control systems typically will specify
products from a list of pre-approved systems.
Vegetation options to provide a complete and stable
facing solution can be specified by the agency or by
Tensar, but supply of the vegetation is by others.
2.4 System Supply
Stenter
The Sierra Slope Retention System is a complete
package system, including materials, engineering
design and on-site technical assistance. All material
components are proven, and are provided with
quality assurance documentation.
The Tensar Process
Figure 2.2 — Processing Tensar Geogrids
2.3.2 Drainage Composite
Drainage composite consists of a geotextile bonded
to both sides of an integrally formed polyethylene
geonet structure with uniform channels, open area,
and thickness to assure uniform flow throughout
the structure.
2.5 System Approval
The recent growth of geosynthetic reinforcement
types and suppliers of such geosynthetics requires
consideration of different alternatives prior to
preparation of contract documents so that contractors
are given clear direction as to which systems
are acceptable. The FHWA has outlined proposed
guidelines for the review and approval of
reinforced slope systems4. The following sections
are based on those recommendations.
2.3.3 Erosion Control System
The erosion control system is generally composed
of a combination of long-term nondegradable Turf
Reinforcement Mats (TRMs), structural geogrids,
SierraScape™ facing elements, geotextile or other
approved facing products. These materials can be
used alone or in combination.
A) A supplier or their representative requests in
writing prior to bid to be placed on this list.
B) The Agency approves the system and the
supplier based upon the following considerations:
i) The geosynthetic reinforcement, drainage
details, and erosion control system for the
system be reviewed and approved for use
as a complete system.
Tensar Earth Technologies offers two TRM
products, TM3000 and TB1000. Each are typically
specified for a particular project based on local soil
types, climate, vegetation, slope angle, aesthetics,
and maintenance considerations. For more
information on either product, please see Tensar
Earth Technologies’ TRM Brochure. You may
order a copy by calling 800-TENSAR-1,
e-mailing [email protected], or visiting
www.tensarcorp.com.
ii) The supplier must have a large enough
operation and necessary experience to
supply and support the construction on
a timely basis.
3
iii) Because the proposed applications are
for critical structures, past experience in
construction must be documented.
Suppliers shall provide certificate of
insurance showing adequate professional
engineers “Errors and Omissions”
insurance.
To facilitate review by the Agency, the supplier
must submit a package which satisfactorily
addresses the following items:
A) System development and year it was
commercialized
B) Organization structure of the supplier of the
system including specific engineering and
construction support personnel
C) Limitations and disadvantages of system
D) List of users including names, addresses,
and telephone numbers
E) Erosion control details as a function of climactic,
geographic, and slope steepness features
F) Sample material and construction control
specifications - showing material type, quality,
certifications, field testing, and placement
procedures
G) A well documented field construction manual
describing in detail, and with illustrations
where necessary, the step by step construction
sequence (copies of this manual should also
be provided to the contractor and the project
engineer at the beginning of the slope
construction)
H) Typical unit costs, supported by data from
actual projects
I)
J)
Detailed information on slope design and
slope stability analysis techniques
Material acceptance and rejection criteria:
as outlined in Appendix A of this document.
Actual test data must be provided to substantiate
adherence to the FHWA guidelines
3.0 SIERRA SLOPE DESIGN
3.1 Design Standards
Design requirements for MSE slope structures
are set forth in FHWA NHI-00-043, “Mechanically
Stabilized Earth Walls and Reinforced Soil Slopes
Design and Construction Guidelines.” Reference
is made to applicable American Society for Testing
of Materials (ASTM) test standards for the erosion
control system, geogrid reinforcement, and
drainage composite materials. Applicable
Geosynthetic Research Institute (GRI) test standards
and standards of practice are also referenced where
ASTM standards do not yet exist.
3.2 Terminology
A mechanically stabilized earth (MSE) slope
consists of six major components: 1) reinforced
slope fill; 2) random backfill behind the reinforced
zone; 3) foundation soil; 4) structural geogrid
reinforcement; 5) internal drainage element; and
6) erosion control system (Figure 2.1).
3.3 Design Overview
The Sierra Slope Retention System is designed so
that it is stable, both internally and externally.
Internal stability requires that the reinforced soil
structure is coherent and self-supporting under
the action of its own weight and any externally
applied forces. This is accomplished through
stress transfer from the soil to the structural
geogrid reinforcement by friction and passive
resistance mobilized by interlock.
The self-supporting gravity mass is created by
the structural geogrid reinforced soil. The
erosion control system is used to prevent surface
sloughing of the slope face, provide an aesthetic
exterior finish and can also facilitate compaction
of the reinforced slope fill.
The steps in the design of a Sierra Slope Retention
System are:
❿ Qualifying geogrid design assumptions
❿ Defining soil, geometry, reinforcement, and
loading parameters
❿ Determining slope stability calculations
❿ Qualifying assumptions for internal drainage,
erosion control system, and landscape design
❿ Developing construction drawings & specifications
4
In total, stress (undrained or short-term) analysis
failure due to shear stresses and increased pore
pressure during construction is assumed. This
situation occurs in clays when pore water pressure
induced by construction has not had time to
dissipate. In this case, the shear strength of the
soil is attributed only to cohesion (i.e. = 0).
3.3.1 Design Assumptions
The design methods presented herein are directly
applicable to each Sierra Slope meeting the
following assumptions:
1. The soil parameters for the reinforced,
retained, and foundation soils are defined.
Reinforced fill may include all highway
embankment construction fills and is not
limited to select or granular backfill.
Effective stress (drained or long-term) analysis is
used for most natural slopes and embankments.
Pore pressures are assumed to be in equilibrium
and are determined by the groundwater table
or a known steady flow pattern. When using
effective stress parameters, attention to the type
of soil test and expected in-situ soil conditions are
particularly important.
2. Design strength (Ta) of the geogrid reinforcement
is approved by the agency prior to design
based on FHWA Guidelines4 with consideration
of installation damage, creep, chemical and
biographical degradation, and joints.
3. Geogrid-soil interaction coefficients (Ci) for
the structural geogrid are approved by the
agency prior to design based on review of
pullout tests using GRI:GG5 test methods5
conducted with representative soils or site
specific testing.
3.3.3 Geometry
For a typical slope, the slope height, H (ft or m),
slope angle (degrees), and uniform surcharge, q
(lb./ft2 or kN/m2), are illustrated in Figure 2.1.
Complicated geometries such as broken back
slopes, transition slopes or unusual foundation
conditions can also be designed. The dimensions and
slope angles for these geometries must be known.
In addition, a value for minimum vertical spacing
between geogrid layers, smin (ft or m), is required.
As a construction expedient smin is usually
set equal to the soil lift thickness to be used
during construction.
4. Soil reinforcement is provided by horizontal
layers of Tensar Geogrids as outlined on
project specific design drawings.
5. Any loads anticipated above and behind
the reinforced zone are accounted for in
the design.
3.3.4 Structural Geogrid Reinforcement Parameters
The Sierra Slope Retention System consists of
Tensar Geogrids arranged in horizontal planes in
the backfill to resist outward movement of the
reinforced soil mass. Geogrids transfer stress
to the soil through passive soil resistance on
transverse members of the grid and friction
between the soil and horizontal surfaces of the
geogrid6. Geogrid long-term design strength (Ta)
is determined by long-term creep testing.
Durability factors include site damage, chemical
degradation, and biological degradation. The
degradation caused by these factors may result in
either a decrease in tensile strength of the geogrid
or a decrease in tensile strength of the geogrid/
soil interaction (coefficient of interaction, Ci).
Values for Ta and Ci should be selected based on
the geogrid and soil type used in the reinforced
slope fill. The methods for quantifying these
parameters are presented below with detailed
discussion in Appendices A and B.
6. Positive drainage is provided to assure no
hydrostatic forces develop in the reinforced
zone.
7. If seismic forces are to be considered in this
design, the appropriate gravitational force
must be defined.
8. Slope angle, surficial stability and facing
material/vegetation selection must be
considered in the design of the erosion
control system.
3.3.2 Total Stress vs. Effective Stress Parameters
An important element of slope stability analysis
is soil shear strength. When choosing value(s) it may
be necessary to consider both total and effective
stresses. These analyses are relevant to short-term
(or end-of-construction) stability and long-term
stability, respectively. Prior to performing a
design, available soil information from testing
should be appropriately classified into one of
these two categories.
5
For Sierra and all other MSE slopes, the allowable
geogrid design strength 4Ta is:
Ta =
Ta
TULT
RFCR
RFID
RFD
TULT
RFCR x RFID x RFD
= allowable geogrid tensile strength, for
use in stability analyses
= ultimate geogrid tensile strength per
ASTM D6637
= reduction factor for creep rupture and
ratio of TULT to creep rupture strength
(dimensionless)
= reduction factor for installation damage
(dimensionless)
= reduction factor for durability/aging
(dimensionless)
3.3.5 Slope Stability
The techniques used for analysis of Tensar MSE
slopes are an extension of routine slope stability
procedures. An MSE slope, however, is more
complex than an unreinforced slope and requires
more steps in the analytic process. Permanent,
critical, geogrid reinforced structures should
be designed using comprehensive slope stability
analysis. A structure may be considered
permanent if its design life is greater than 5 years.
A reinforcement application is considered critical
if there is mobilized tension in the reinforcement
for the life of the structure, if failure of the
reinforcement results in failure of the structure,
or if the consequences of failure include personal
injury or significant property damage7.
Failure modes of MSE slopes include4:
i) internal, where the failure plane passes
through the reinforcing elements
ii) external, where the failure surface passes
behind and underneath the reinforced mass
iii) compound, where the failure surface passes
behind and through the reinforced soil mass
A MSE slope may have several potential
“critical” failure planes8. Tensar Sierra Slope
Retention System designs consider the number of
reinforcement layers, design tensile force of each
layer, anchorage requirements, and length of the
reinforcing layers which affect the location of the
critical failure plane. The critical failure surface will
most likely not be the same as the unreinforced
failure surface with the lowest factor of safety.
Therefore, a computerized search of all potential
failure surfaces within the “safe” unreinforced
failure zone should be conducted. Additionally,
safety factors may be plotted as contours of safety
factors. The contours should be drawn on the field
of failure circle centroids8. This plotting assists in
locating the various centroids of failure circles with
low safety factors, and in locating all potential
critical failure surfaces (Figure 3.1).
Figure 3.1 — Typical Critical Failure Surfaces for an MSE Slope
Comprehensive slope stability analysis requires
the use of a computer program. TET uses a slope
stability computer program that incorporates the
stabilizing effects of Tensar Geogrid reinforcement
into the analysis of a slope using the Simplified
Bishop Method of Slices. This computer program
directly incorporates tension of each reinforcement
layer into the safety factor computations. The
program includes anchorage, or pullout length
requirements in computation of mobilized
reinforcement tension.
3.3.6 Analysis Methods
3.3.6.1 Limit Equilibrium Methods. The object of
slope stability analysis is to quantify the possibility
of excessive deformation or collapse of the slope or
embankment. The accurate prediction of deformation
requires definition of many hard-to-evaluate
parameters and use of complex analytical methods
not available to most engineers. Thus, analysis using
limit equilibrium to determine a factor of safety
against collapse of the slope is most commonly
used. It is assumed by requiring an adequate factor
of safety through limit equilibrium methods that
deformations of the slope will be limited to an
acceptable level.
6
3.3.6.2 Simplified Bishop Method of Slices. The
Bishop Method of Slices may be used to analyze
the stability of slopes with varying soil properties,
pore water pressure, and an irregular geometry.
The failure surface is assumed circular and the
soil mass is divided into vertical slices. The forces
on each slice are evaluated using limit equilibrium
methods (i.e. summing moments about the center
of rotation of the failure plane).
The forces acting on each slice of a slope include
the weight of the slice, W; normal and shear forces
acting on the base of the slice, P and S; normal
and shear forces acting on the vertical sides of
the slice, E and T. (Figure 3.2) The vertical normal
and shear forces are related to deformation and
stress-strain characteristics of the soil which are
not easily evaluated. To achieve a statically
determinate system, the “simplified” method
assumes side forces to be equal with coincidental
lines of action. Thus, the forces cancel each other
and are set equal to zero in calculations. The
effect on the accuracy that this assumption has
on the determination of the factor of safety of the
slope is in the range of 1% to 10%.
T
E
W
E
T
S
Higher factors may also be desired in cases
where slopes are supporting structures. Lower
safety factors may be acceptable for temporary
and/or noncritical structures.
3.3.8 Seismic Design4
Under seismic loading, a reinforced soil slope is
subjected to dynamic forces in addition to static
forces. The allowable tensile stress of the geogrid
reinforcement may be increased for short-term
seismic loading conditions9,10.
The recommended method of seismic analysis
for earth slopes is pseudo-static analysis with a
slope stability computer program. A horizontal
pseudo-static force, which is some percentage
of the slice weight, is applied to each slice in the
analysis. A vertical force may also be simultaneously
applied, if dictated by local codes or practice.
Internal, external, and compound failure modes
should be analyzed with an additional horizontal
pseudostatic acceleration force included. The
target safety factor is typically taken as greater than
or equal to 1.1 for these potential failure modes.
The magnitude of the pseudo-static force
coefficient will typically be dictated by local codes
and/or practice. A detailed map seismic risk is
presented in the AASHTO Bridge Manual (1991).
Pseudo-static techniques may not be appropriate
for areas subject to high seismic loadings or slopes
adjacent to critical structures10. Comprehensive
dynamic analysis procedures should be utilized
for these cases.
Use of pseudo-static dynamic earth pressures
according to the Mononobe-Okabe procedure may
be acceptable for slopes steeper than approximately
seventy degrees (70°)9. This pseudo-static analysis
was developed for retaining walls and assumes
that the soil behind the wall behaves as
a rigid body. The factor of safety against failure
by outward sliding should be greater than or
equal to 1.1. This wall analysis is also sensitive
to the slope angle of the retained backfill, as
discussed in Supplement A, Standard Specifications
for Seismic Design of Highway Bridges, of the
AASHTO Bridge manual (1991) and by Seed and
Whitman11.
P
Figure 3.2 — Forces Acting on a Typical Slice
3.3.7 Safety Factors
The factor of safety for slope stability should be
adequate to address all uncertainties in the
assumptions and design9. Recommended
minimum stability factor of safety is 1.3 against
external, deep seated failures; compound failure
surfaces; and internal failure4, unless local codes
require a higher value.
This safety factor is the minimum recommended
for permanent structures. Higher factors are
recommended in the absence of thorough
geotechnical investigation and analysis.
7
3.4 Soil-Reinforcement Interaction
Two types of soil-reinforcement interaction
coefficients or interface shear strengths must be
determined for design: pullout coefficient and
direct shear coefficient12. Pullout coefficient is
used in stability analysis to compute mobilized
tensile force at the front and tail of each
reinforcement layer. The direct shear coefficient
is used in checking factors of safety against
outward sliding of the reinforced mass on top of
any layer of reinforcement. A detailed discussion
on the use of these coefficients is provided by
the FHWA4.
A test method standardizing laboratory pullout
testing of geogrids (GRI:GG5) was published by
the Geosynthetic Research Institute (GRI) in 19915.
Determination of an interaction coefficient is
defined as either short-term or long-term by this
standard, and is dependent on the method of
pullout force application. Short-term testing with
controlled strain rate, controlled stress rate, or
incremental stress methods of pullout force
application provide short-term interaction coefficients.
A constant stress (creep) method of pullout force
application yields a long-term pullout coefficient.
Typical design practice is to define an interaction
coefficient with a controlled strain (deformation)
method of testing, per the GRI test method, and
apply the coefficient to long-term designs.
TET has performed long-term pullout tests of
both singular and composite manufacture type
of geogrids13. The results of approximately 1,000hour sustained load pullout tests were compared
with a quick pullout test (strain rate of 1 mm/min)
to determine an efficiency of the geogrid with
respect to pullout. Efficiency was computed as the
ratio of long-term coefficient of interaction to the
short-term coefficient of interaction. Use of quick
tests to define long-term pullout capacity for use
in design is not recommended. This practice
inherently assumes that an efficiency of 100% or
greater exists between long-term and short-term
pullout capacity.
However, the pullout test results presented by
Collin and Berg13, demonstrate that it can not be
assumed that the long-term pullout performance
of geogrids can be determined through quick
tests. Short-term coefficient of interaction Cis
may not be equal to the long-term coefficient of
interaction Cis. This testing substantiates that
“through-the-junction” creep testing outlined in
GRI:GG3 is critical when determining the longterm coefficient of interaction through quick tests.
3.5 Internal Water Drainage
Uncontrolled subsurface water seepage can
decrease stability of MSE slopes and could
ultimately result in slope failure. Hydrostatic
forces on the rear of the reinforced mass will
decrease stability against sliding failure.
Uncontrolled seepage into the reinforced mass
will increase the weight of the reinforced mass
and may decrease the shear strength of the soil,
hence decrease stability. Seepage through the
mass can reduce pullout capacity of the geogrid
at the face and increase soil weight, creating
erosion and sloughing problems. A detailed
discussion of internal drainage is provided by
the FHWA4.
Design of subsurface water drainage features
must address flow rate, filtration, placement, and
outlet details. Drains are typically placed at the
rear of the reinforced mass. Lateral spacing of
outlets is dictated by site geometry, expected flow,
and existing agency standards. Outlet design
should address long-term performance and
maintenance requirements as applicable.
Drainage composites can be utilized in subsurface
water drainage design for Sierra Slopes. The use
of geocomposite drainage is briefly addressed in
this document with specifications provided in
Section 7.0. Drainage composites should be
designed with consideration of:
i) peel strength of the geotextile from the geonet
ii) reduction of flow capacity due to intrusion of
geotextile into the core
iii) inflow/outflow capacity
iv) filtration characteristics between the soil and
geotextile
A measurement of peel strength of the geotextile
from the geonet is an important consideration
to insure that a sheer failure does not occur from
the load created by the backfill on the drainage
composite. ASTM F904-84 test procedure
Comparison of Bond Strength or Ply Adhesion
of Similar Laminates made from Flexible
Materials should be followed.
8
Intrusion of the geotextiles into the core and
inflow/outflow capacity should be measured
with a substained transmissivity test. The
ASTM D 4716 test procedure (1987), Constant
Head Hydraulic Transmissivity of Geotextiles and
Geotextile Related Products, should be followed.
Load should be maintained for 50 hours or until
equilibrium is reached, whichever is greater, at a
pressure equal to or greater than the expected
pressure for the specific application. Flow rate
is measured at a standard gradient of 1.0. In
addition, slope stability analysis should account
for interface shear strength along a geocomposite
drain. The geotextile that is laminated to the
geonet should be designed to act as a filter to
prevent the migration of soil. Guidelines for the
filter design are provided in the FHWA Guidelines4.
Special emphasis on the design and construction
of subsurface drainage features is recommended
for MSE slope structures. Drainage is critical
for maintaining slope stability. Redundancy in
the drainage system is also recommended.
with seepage parallel to the slope face can
develop. Intermediate layers of secondary
reinforcement are usually required at the face of
reinforced slopes to control surficial slope failures.
Design is dependent upon soil type, slope angle,
slope height, and primary reinforcement spacing.
The intermediate layers of reinforcement aid in
achieving compaction at the face, thus increasing
soil shear strength and resistance to erosion. These
layers also act as reinforcement against shallow or
sloughing types of slope failures. Intermediate
reinforcement is typically placed on each or every
other soil lift, except at lifts where primary structural
reinforcement is placed. Intermediate reinforcement
is also placed horizontally adjacent to primary
reinforcement, and at the same elevation as the
primary reinforcement, when primary reinforcement
is placed less than 100% coverage in plan view.
The intermediate reinforcement typically extends
3 to 6 feet into the fill from the face.
Slopes steeper than 1:1 typically require facing
support during construction. TET’s SierraScape
facing elements are typically used. SierraScape
facing elements are mechanically connected to
the geogrid reinforcement providing enhanced
protection against surficial failure during and
immediately following construction.
3.6 Surface Drainage & Erosion Protection
Stability of a slope can be threatened by erosion
due to surface water runoff. Erosion rills and
gullies can lead to surface sloughing and possibly
deep seated failures. Erosion control and
revegetation measures must be an integral part
of all reinforced slope system designs and
specifications.
3.6.3 Landscape Design Considerations
Unlike conventional MSE wall systems, the Sierra
Slope Retention System can be designed for a
wide variety of visual impressions. Sierra Slopes
can be faced with grass or wildflowers, revegetated
to a natural state or landscaped as mulched
ornamental bedding. Sierra Slopes can also be
combined with traditional flat fill slopes to create
contoured grades that are indistinguishable from
adjacent natural slopes.
3.6.1 Surface Water Drainage
Surface water runoff should be collected above
the reinforced slopes and channeled or piped
below the base of the slope. Standard agency
drainage details should be utilized. It is also
important not to allow surface waters to infiltrate
from the top of the slope into the reinforced slope
fill. This water will tend to percolate out of the
slope face potentially causing surficial slumps.
3.6.2 Surficial Stability
In-depth discussions of surficial slope failure
mechanisms have been presented by Terzaghi and
Peck (1967)14, Campbell (1975)15, and Theilen and
Collin (1993)16. These failures are usually initiated
by water infiltrating the near surface soils. The
source of this water may be rainfall, broken
utilities, landscape watering, or failure to intercept
upslope drainage. When infiltration exceeds the
transmissivity of the soil, a perched water table
9
The various vegetation options available for the
Sierra Slope Retention System place an emphasis
on choosing the proper landscape design to fit the
site constraints. A low maintenance grassed slope
may work well on a seldom seen highway
downslope, but may be a poor choice for a slope
on a highly visible urban roadway interchange.
A landscaped slope may be a better choice for
the latter site.
Landscape design is usually provided by the
agency. TET can provide local and regional
expertise in landscape design, plant selection,
and erosion control solutions for Sierra Slopes.
3.6.4 Erosion Control Systems
MSE slopes typically are vegetated during or
immediately after construction to prevent or
minimize erosion due to rainfall and runoff on the
face. On sites where vegetation cannot grow (i.e.,
abutments under bridges, below water, desert,
or arid regions) non-vegetated erosion control
systems can be provided. Vegetation requirements
will vary by geographic and climactic conditions
and are therefore project specific. Steep grades can
be difficult locations on which to establish and
maintain vegetative cover. The steepness of the
grade limits the amount of water absorbed by
the soil before runoff occurs. Once vegetation is
established on the face, it must be protected to
ensure long-term survival.
C. Agency chooses vegetation option based on
considerations outlined above.
D. Agency specifies appropriate erosion control
system as a pre-approved system.
The Sierra approach for erosion solutions uses
several predetermined erosion control systems.
This approach is preferable to a component or
material approach, because it can address the
multitude of factors that must be considered in
designing erosion control and facing treatments
and it simplifies the approval process for the
Agency. The erosion control system approach
addresses surficial bare soil erosion control,
vegetation establishment, surficial stability, facing
support during construction, and facing aesthetics.
Consequently, for grassed or wildflower faced
slopes, a long-term nondegradable erosion control
mat that is stabilized against ultra-violet light and
is inert to naturally occurring soil-born chemicals
and bacteria is required. The erosion control mat
serves four functions:
A. Protects the bare soil face against erosion until
vegetation is established
B. Reduces runoff velocity for increased water
absorption by the soil thus promoting longterm survival of the vegetative cover
C. Reinforces the root system of the vegetative
cover to create veneer reinforcement element
for the sod
D. Protects seed and enhances seed germination
and seedling establishment over the design
life of the structure to ensure complete
vegetation cover on the entire slope face.
Sierra Slopes usually employ low maintenance
vegetation options but depending on the site
and actual plant material selected, some
maintenance of vegetation may be required.
3.6.5 Erosion Control System Selection
Selection of the appropriate vegetation and an
erosion control system is a four-step process.
These steps are:
A. Agency determines or designs desired slope
angles based on site constraints, soil types, etc.
B. Agency and/or supplier reviews the
surrounding site for existing vegetation,
visibility factors, and horticultural growing
conditions.
10
Project: Fort Smith
Location: Fort Smith, Arkansas
Owner: City of Fort Smith
Engineer: Mickale, Wagoner & Coleman
Contractor: Forsgren Construction
Constructed: Summer 1996
Max. Height: 22 ft.
4.0 SIERRA EXPERIENCE
Some of the completed Sierra Slope Retention
System projects for government agencies are
summarized below. Additional information,
including contact people, on these projects is
available upon request. An extensive completed
project list for slopes used in property development
is also available upon request.
CALIFORNIA
Project: Highway 84
Location: LaHonda, California
Owner: Cal Trans
Engineer: Cal Trans District 4
Constructed: Fall 1986
Max. Height: 42 ft.; 1:1 slope
ALABAMA
Project: County Rd 81
Location: Ft. Payne, Alabama
Owner: Dekalb County
Engineer: Ladd Environmental Consultants, Inc.
and Gallet & Associates
Contractor: Jackson Paving
Constructed: Winter 1999
Max. Height: 63 ft.; 1:1 slope
ARIZONA
Project: Bush Highway
Location: Maricopa County, Arizona
Owner: Maricopa County, Arizona
Engineer: Maricopa County Highway Department
Contractor: McMurry Bros.
Constructed: Fall 1987
Max. Height: 70 ft.
Project: Carefree Highway
Location: Maricopa County, Arizona
Owner: Maricopa County, Arizona
Engineer: Tensar Earth Technologies, Inc.
Contractor: Ames Construction
Constructed: Spring 1993
Max. Height: 35 ft; 1:1 slope
Project: Highway 9
Location: Felton, California
Owner: Cal Trans
Engineer: Cal Trans District 4
Contractor: Dan Caputo
Constructed: Summer 1992
Max. Height: 46 ft.; 0.5:1 slope
Project: Van Duzen-Peanut
Location: Northern California
Owner: USDA Forest Service
Engineer: FHWA; Central Division
Contractor: Stimpl-Wiehelhaus
Constructed: Fall 1988
Max. Height: 60 ft.; 1:1 slope
COLORADO
Project: I-270
Location: Denver, Colorado
Owner: Colorado DOT
Engineer: Colorado DOT
Contractor: Cat Construction
Constructed: Spring 1994
Max. Height: 14 ft.; 1.25:1 slope
ARKANSAS
Project: Cannon Creek, Highway 16
Owner: Arkansas State Highway and
Transportation Department
Engineer: Raymond Technical
Contractor: Machen Construction
Constructed: Summer 1987
Max. Height: 75 ft.; 2:1 slope repair
FLORIDA
Project: State Road 70 Overpass
Location: Okeechobee, Florida
Owner: Florida DOT
Engineer: Professional Engineering Consultants
Contractor: Sheltra Construction Company
Constructed: Summer 1996
Max. Height: 28 ft.; 1:1 slope
11
Project: State Road Highway 60
Location: Lake Wales, Florida
Owner: Florida DOT
Engineer: Jammal & Associates
Contractor: Mid States Paving
Constructed: Fall 1991
Max. Height: 18 ft.; 1:1 slope
Project: I-75 Weight Station
Location: Wildwood, Florida
Owner: Florida DOT
Engineer: Boyles Engineering
Contractor: DAB Construction
Constructed: Fall 1991
Max. Height: 12 ft.; 1:1 slope
Project: Maitland Pedestrian Overpass
Location: Maitland, Florida
Owner: Florida DOT
Engineer: Sverdup Corporation
Contractor: Martin Paving Company, Inc.
Constructed: Spring 1998
Max. Height: 21 ft.; 1.2:1 slope
Project: State Route 15 Realignment
Location: Debary, Florida
Owner: Florida DOT
Engineer: Greiner & Associates
Contractor: DeWitt Excavating
Constructed: Spring 1993
Max. Height: 30 ft.; 1:1 slope
GEORGIA
Project: Airport Expansion
Location: Atlanta, Georgia
Owner: Atlanta Hartsfield Authority
Engineer: Tensar Earth Technologies, Inc.
Contractor: Gilbert & Southern
Constructed: Fall 1992
Max. Height: 40 ft.; 1:1 slope
Project: I-285
Location: Atlanta, Georgia
Owner: Georgia DOT
Engineer: Georgia DOT
Contractor: C.W. Matthews
Constructed: Fall 1994
Max. Height: 35 ft.; 1.25:1 slope
IDAHO
Project: Kootenai Cutoff
Location: Sandpoint, Idaho
Owner: Idaho DOT
Engineer: Idaho DOT
Contractor: DeAtley Company Inc.
Constructed: Summer 1996
Max. Height: 8 ft.
ILLINOIS
Project: Peck Road
Location: Geneva, Illinois
Owner: Kane County, IL
Engineer: Terracon
Contractor: Plote Construction
Constructed: Spring 2000
Max. Height: 20 to 25 ft.; 2:1 slope
LOUISIANA
Project: I-10
Location: Baton Rouge, Louisiana
Owner: Louisiana DOT
Contractor: Angelo IAFRATI Construction
Constructed: Fall 1997
Max. Height: 19 ft.
KANSAS
Project: I-35 & Johnson Drive Exit
Location: Olathe, Kansas
Owner: Kansas DOT
Engineer: Howard, Needles, Tammen &
Bergendoff
Contractor: Clarkson Construction Company
Constructed: Summer 1988
Max. Height: 15 ft.; 1:1 slope
Project: Route 150
Location: Topeka, Kansas
Owner: Missouri DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: Idecker, Inc.
Constructed: Winter 1998
Max. Height: 52 ft.; 1:2 slope
Project: I-135
Location: Salina, Kansas
Owner: Kansas DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: Clarkson Construction
Constructed: Summer 1999
Max. Height: 20 ft.; 2:1 slope
12
Project: US 50
Location: Kinsley, Kansas
Owner: Kansas DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: APAC
Constructed: 2000
Max. Height: 25 ft.; 1:5-1 slope
Project: State Route 100
Location: Howard County
Owner: Maryland DOT
Engineer: KCI Technologies, Inc.
Contractor: Williams Construction
Constructed: Fall 1994
Max. Height: 50 ft; 1:1 slope
Project: Highway 156
Location: Ellsworth County, Kansas
Owner: Kansas DOT
Engineer: Tensar Earth Technologies, Inc.
Constructed: 2001
Max. Height: 9 ft.; 2:1 slope
MASSACHUSETTS
Project: Pearl Street
Location: Braintree, Massachusetts
Owner: Mass Bay Transit Authority (MBTA)
Engineer: Tensar Earth Technologies, Inc.
Contractor: DeMatteo Construction
Constructed: Fall 1996
Max. Height: 25 ft.
KENTUCKY
Project: Cincinnati Airport
Location: Hebron, Kentucky
Owner: USPS
Engineer: QORE
Contractor: James H. Gray
Constructed: Winter 1999
Max. Height: 18 ft.
MICHIGAN
Project: Highway M44
Location: Grand Rapids, Michigan
Owner: Michigan DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: K & R Contracting
Constructed: Summer 1991
Max. Height: 40 ft.; 1:2-1 slope
Project: U.S. Highway 23
Location: Prestonsburg, Kentucky
Owner: Kentucky DOT
Engineer: Bowser - Morner
Contractor: Bizzack Construction
Constructed: Spring 1992
Max. Height: 30 ft.; 1:1 slope
MINNESOTA
Project: Blake Road
Location: Edina, Minnesota
Owner: City of Edina
Engineer: STS Consultants
Contractor: C.S. McRossan
Constructed: Fall 1992
Max. Height: 10 ft.; 0.125:1 vegetated wall
MAINE
Project: Poland Springs
Location: Poland Springs, Maine
Owner: Perrier Group of America
Engineer: Pinkham & Greer and Tensar
Earth Technologies, Inc.
Contractor: White Brothers, Inc.
Constructed: Summer 1996
Max. Height: 37 ft.; 1:1 slope
Project: E-80 Cooper Train Loading
Location: Kellog, Minnesota
Owner: CPRR
Engineer: Tensar Earth Technologies, Inc. and
CPRR
Contractor: Lunda Corporation
Constructed: Summer 1999
Max. Height: 22 ft.; 1:1 slope with temporary wall
MARYLAND
Project: Route 410
Location: Prince George City, Maryland
Owner: Maryland DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: Driggs Corp.
Constructed: Summer 1989
Max. Height: 48 ft.; 1.5:1 slope
13
Project: Maryland Hts. Subdivision
Location: Natchez, Mississippi
Owner: Natchez Housing Authority
Engineer: Jordan, Kaiser & Sessions
Contractor: Great River Stone
Constructed: Fall 1991
Max. Height: 45 ft. 1:1 slope
Project: US 285
Location: New Mexico
Owner: New Mexico DOT
Engineer: Highway Department and Lewis
Burger & Associates
Contractor: Nielsons Inc.
Constructed: Summer 1996
Max. Height: 40 ft.
MISSOURI
NEW YORK
Project: Elm Street Overpass
Location: St. Louis, Missouri
Owner: Missouri DOT
Engineer: Midwest Testing Engineer
Contractor: Fred Weber Contracting
Constructed: Fall 1992
Max. Height: 40 ft.; 50° Bridge Abutment
Project: Ithaca County Courthouse
Location: Ithaca, New York
Owner: Ithaca County
Engineer: Empire Soils
Constructed: Summer 1992
Max. Height: 10 ft. Vegetated Wall
MISSISSIPPI
MONTANA
Project: Dickey Lake
Location: Lincoln Cty. , Montana
Owner: Montana Highway Department
Engineer: Midwest Highway Department
Constructed: Summer 1990
Max. Height: 60 ft.; 1:1 slope
NEBRASKA
Project: Davis Creek Dam
Location: Ord, Nebraska
Owner: Bureau of Reclamation
Engineer: Bureau of Reclamation
Contractor: Gilbert Central Corporation
Constructed: Summer 1990
Max. Height: 29 ft., 1:1 slope
NEW HAMPSHIRE
Project: Route 3A
Location: Hooksett, New Hampshire
Owner: New Hampshire DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: R.S. Audley
Constructed: Fall 1990
Max. Height: 40 ft. 1.25:1 slope
NEW MEXICO
Project: US 64
Location: Dulce, New Mexico
Owner: New Mexico DOT
Engineer: Highway Department
Contractor: Weeminuche Construction Authority
Constructed: Winter 1999
Max. Height: 22 ft.
Project: Route 174
Location: Ononadaga County, New York
Owner: New York DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: Sut-Kote Construction
Constructed: Summer 1994
Max. Height: 33 ft.; 1.25:1 slope
NORTH CAROLINA
Project: Bethlehem Road
Location: Rocky Mount, North Carolina
Owner: North Carolina DOT
Engineer: North Carolina DOT
Contractor: Barnhill Construction
Constructed: Spring 1991
Max. Height: 25 ft.; 1.1 slope
Project: Robbinsville Tellico Plains Road
Location: Robbinsville, North Carolina
Owner: FHWA
Engineer: FHWA
Contractor: Robbinsville Contracting
Constructed: Fall 1993
Max. Height: 40 ft.; 1.5:1 slope
Project: Route 74
Location: Graham City, North Carolina
Owner: North Carolina DOT
Engineer: North Carolina DOT
Contractor: Gilbert Southern
Constructed: Fall 1999
14
NORTH DAKOTA
Project: RM 2222
Location: Austin, Texas
Owner: Texas DOT
Engineer: Tensar Earth Technologies, Inc.
Contractor: Austin Filter Systems
Constructed: Spring 1990
Max. Height: 10 ft.; 1:1 Temporary Wall
Project: Teddy Roosevelt National Park, ND
Owner: National Park Service
Engineer: National Park Service
Constructed: Summer 1986
Max. Height: 20 ft.; 2:1 landslide repair
OHIO
Project: Ohio Turnpike
Location: Cleveland, Ohio
Owner: Ohio DOT
Constructed: Spring 2000
Max. Height: 60 ft.; 1:1 slope
VERMONT
Project: Gold Hill Road
Location: Montpelier, Vermont
Owner: City of Montpelier
Engineer: Pinkham Engineering Associates
Contractor: Morrill Construction
Constructed: Fall 1992
Max. Height: 75 ft.; 1:1 slope
PENNSYLVANIA
Project: Pennsylvania Turnpike
Location: Morgantown, Pennsylvania
Owner: Penn. Turnpike Authority
Engineer: GeoMechanics
Contractor: Stabler Construction
Constructed: Summer 1988
Max. Height: 35 ft.; 1:1 slope
Project: Route 30
Location: Townshed, Vermont
Owner: Vermont Agency of Transportation
Engineer: Vermont Agency of Transportation
Contractor: Miller Construction
Constructed: Summer 1991
Max. Height: 35 ft.; 1:1 slope
SOUTH CAROLINA
Project: Highway 17
Location: North Charleston, South Carolina
Owner: South Carolina DOT
Engineer: F & ME
Contractor: Banks Construction
Constructed: Spring 1997
Max. Height: 20 ft.
WASHINGTON
Project: 140th Avenue
Location: Kent, Washington
Owner: King County
Engineer: Hong West Associates and
Parsons Brinckerhoff
Contractor: Scarsella Brothers
Constructed: Fall 1999
Max. Height: 96 ft.; 2:1 slope
Project: Route 5
Location: York County, South Carolina
Owner: South Carolina DOT
Engineer: Foundation and Material Engineers
Contractor: Jenkins Construction
Constructed: Fall 1990
Max. Height: 50 ft.; 2:1 landslide repair
Project: State Route 20
Location: Concrete, Washington
Owner: Washington DOT
Engineer: Washington DOT
Constructed: Summer 1991
Max. Height: 60 ft.; 1:1 slope
TEXAS
Project: Combat Arms Training Facility
Location: Dyers AFB, Texas
Owner: Corps of Engineers
Engineer: Lockwood Greene
Constructed: Summer 1988
Max. Height: 24 ft.; 1:1 slope
WEST VIRGINIA
Project: Buckhannon Airport
Location: Buckhannon, West Virginia
Owner: Upshur City Airport
Engineer: HC Mutting & Chapman
Technical Group
Contractor: Kimberly Industries
Constructed: Winter 1996
15
Project: Highway 52
Location: McDowell County, West Virginia
Owner: West Virginia DOT
Engineer: West Virginia DOT
Contractor: Alan Stone
Constructed: Summer 1984
Max. Height: 35 ft.; 1.5:2 Landslide Repair
Project: Tri-State Airport
Location: Kenova, West Virginia
Owner: Tri-State Airport Authority
Engineer: Delta Engineers
Contractor: McCoy Construction
Constructed: Winter 1996
ONTARIO
Project: Highway 410
Location: Brampton, Ontario
Owner: Ministry of Transportation
Engineer: Ministry of Transportation
Constructed: 1983
Max. Height: 26 ft.; 1:1 slope
Project: Highway 407
Owner: Ministry of Transportation
Engineer: DS-Lea Associates, LTD
Contractor: Graham Bros. Construction
Constructed: Fall 1994
Max. Height: 37 ft.; 1:1 slope
16
5.0 ADVANTAGES & DISADVANTAGES
5.1 Advantages
There are several advantages associated with the
use of a Sierra Slope Retention System versus
reinforced MSE walls or cast-in-place walls. Some
of the safety, performance, construction, aesthetic,
and cost advantages are listed as follows:
❿ The Sierra Slope Retention System provides
an attractive, natural appearance, with the use
of vegetation as a facing element versus
concrete units used in MSE wall systems.
❿ Sierra Slopes can be built at varying grades
so that the entire RSS structure blends into
existing grades. Concrete MSE wall structures
create monolithic structures which can clash
with the natural landscape.
❿ The Sierra System is a synergistic system, with
consistent engineering through design, material
manu facture, and construction. Agencies can
specify Sierra with confidence knowing that
the components will create a successful
RSS structure.
❿ The Sierra Slope Retention System offers a
significant in-place cost savings (up to 50%)
over MSE walls (see Figure 6.1).
❿ A fairly wide range of backfill soils (i.e.
typical highway embankment fills) have been
successfully used with the Sierra System.
Suitable quality backfill material can frequently
be found on or near the construction site and
thus need not be imported, potentially resulting
in significant cost savings.
❿ Tensar Geogrids are inert and non-conductive;
therefore, they provide excellent resistance to
degradation in highway environments,
particularly in the presence of decier salts and
stray current environments.
❿ The Sierra System allows an Agency roadway
design group greater flexibility in balancing
cut and filling quantities on a job site.
❿ The deformation response of a Tensar
Geogrid reinforced soil mass and the absence
of concrete units provide a Sierra Slope with
the flexibility to absorb unexpected large
17
lateral and vertical deformations. This flexibility
also makes the system ideal for use on sites
with poor foundations or seismic activity.
❿ The vegetated Sierra surface provides better
sound attenuation than smooth concrete
surfaces.
❿ Construction is accelerated by the lack of
need for forms or temporary bracing systems.
❿ Backfill placement and compaction proceeds
quickly since no concrete facing elements
are required.
❿ Slope construction does not require specialized
contractors, skilled labor, or specialized
equipment.
❿ Tensar Geogrids, drainage composites, and
TRMs are relatively light and easy to handle.
❿ Post-construction maintenance costs such as
cleaning and graffiti removal are avoided.
5.2 Possible Disadvantages
There are relatively few disadvantages associated
with the Sierra Slope Retention System. Possible
disadvantages are listed below along with methods
to mitigate these potential disadvantages.
❿ The Sierra System may be new to Agency
construction inspectors. Therefore, a preconstruction meeting of TET engineers, agency
engineers and inspectors may be required to
review the proper construction techniques.
❿ The Sierra System may be new to a contractor.
Therefore, site assistance, in addition to that
routinely provided on projects, may be
required to educate the labor force on the
proper construction technique.
❿ The Sierra System offers the option of a
vegetation facing system that may require
plant selection and landscape design aspects
which are unfamiliar to some engineers or
agencies familiar with the MSE wall structures.
TET has the necessary expertise to address
these issues so that highway agencies can
specify Sierra with confidence.
In summary, the Sierra Slope Retention System
constructed in accordance with this design
specification will provide low cost, reliable, safe,
and durable structures. The advantages of this
system far outweigh any potential disadvantages.
6.0 TYPICAL COSTS
Typically, the in-place cost of a Sierra Slope
Retention System is quoted per unit area of
vertical face projection (i.e., per sq ft).
This pricing includes:
❿ Engineering and construction drawings
❿ All structural geogrid, drainage composite,
and erosion control system materials
❿ Installation of structural geogrids, drainage
composite, and erosion control system
❿ Placement and compaction of reinforced
backfill soils
❿ Material and installation costs of vegetation
INDICATED WITH A ## SYMBOL AND MUST
BE DELETED FROM THE FINAL SPECIFICATION.
IT IS ASSUMED THAT THE GENERAL
CONDITIONS BEING USED ARE AIA A201-87.
SECTION NUMBERS ARE FROM THE 1995
EDITION OF MASTER FORMAT.
FOR THE MOST RECENT VERSION OF THIS
SECTION, PLEASE VISIT OUR WEB SITE AT
WWW.TENSARCORP.COM.
7.1 General
7.1.1 Summary
Section includes furnishing and testing materials,
and the design and construction of a Mechanically
Stabilized Earth (MSE) slope retention system.
Work consists of:
1. Furnishing structural geogrid reinforcement,
drainage composite, and erosion control
system as shown on the construction drawings.
2. Storing, cutting, and placing structural
geogrid reinforcement, drainage composite,
and erosion control system as specified herein
and as shown on the construction drawings.
3. Furnishing sealed design calculations and
construction drawings for MSE slope; providing
supplier representatives for pre-construction
meeting with the Contractor and Engineer.
4. Excavation, placement, and compaction
of reinforced fill and backfill material as
specified herein and as shown on the
construction drawings.
## EDIT LIST BELOW TO CONFIRM PROJECT
REQUIREMENTS. VERIFY SECTION NUMBERS AND TITLES.
7.1.1.1 Related Sections
A. Section 2200 – Site Preparation
B. Section 02300 – Earthwork
Figure 6.1 — Sierra Cost Comparison
7.0 SPECIFICATION FOR
MECHANICALLY STABILIZED
EARTH RETENTION SYSTEM
THIS SECTION IS WRITTEN IN CSI 3-PART
FORMAT AND IN CSI PAGE FORMAT. NOTES
TO THE SPECIFIER, SUCH AS THIS, ARE
7.1.1.2 Alternates
A. Geotextile materials will not be considered as
an alternate to geogrid materials. Geotextile
may be used to provide separation, filtration,
or drainage; however, no structural contribution
will be attributed to the geotextile.
B. Alternate geogrid materials shall not be used
unless submitted to the Engineer and
approved in writing by the Engineer at least
7 days prior to the bid letting. The Engineer
shall have absolute authority to reject or
accept alternate materials based on the
18
requirements of this Section and the Engineer’s
judgment. Polyester geogrids, whether coated
or uncoated, will not be approved for use
in calcareous, alkaline, or highly acidic
environments, including lime-treated or
cement-treated soils, crushed lime rock, or
soils potentially exposed to leachate from
cement, lime, or de-icing salts. In no case shall
polyester geogrids be used in soils with a
pH > 9. In order to be considered, submittal
packages for alternate geogrid materials
must include:
1. A list of 10 comparable projects that are
similar in terms of size and application,
are located in the United States, and
where the results of using the specific
alternate geogrid material can be
verified after a minimum of 3 years of
service life.
2. A sample of alternate geogrid material
and certified specification sheets.
3. Recommended installation instructions.
4. An explanation of engineering
techniques used and sample design
drawings and calculations prepared and
sealed by a Professional Engineer
licensed in the applicable state.
5. Additional information as required by
the Engineer.
D4716-95
D4759-92
D5262-97
D5818-95
D 6637-01
F904-91
Test Method for Constant Head Hydraulic
Transmissivity (In-Plane Flow) of Geotextiles
and Geotextile Related Products
Practice for Determining the Specification
Conformance of Geosynthetics
Standard Test Method for Evaluating
Unconfined Tensile Creep Behavior of
Geosynthetics
Practice for Obtaining Samples of
Geosynthetics from a Test Section for
Assessment of Installation Damage
Standard Test Method for Determining
Tensile Properties of Geogrids by the
Single or Multi-Rib Test Method
Standard Test Method for
Comparison of Bond Strength or Ply
Adhesion of Similar Laminates Made
from Flexible Materials
B. Geosynthetic Research Institute (GRI)
GG2-87
GG4-91
GG5-91
GG7
GG8
7.1.2 References
## DELETE REFERENCES NOT USED IN PART 7.2
Standard Test Method for Geogrid
Junction Strength
Determination of the Long-Term Design
Strength of Geogrids
Standard Test Method for “Geogrid Pullout”
Standard Test Method for Carboxyl End
Group Content of Poly (Ethylene
Terephthalate) (PET) Yarns
Determination of the Number Average
Molecular Weight of Poly(Ethylene
Terephthalate) (PET) Yarns Based on a
Relative Viscosity Value
OR PART 7.3.
C. U.S. Federal Highway Administration
(U.S. FHWA)
A. American Society for Testing and Materials
(ASTM)
D374-94
D1388-96
D2455-96
D4595-94
D4355-92
D4603-96
Test Methods for Thickness of Solid
Electrical Insulation
Standard Test Method for Stiffness of
Fabrics, Option A
Standard Test Method for Identification
of Carboxylic Acids in Alkyd Resins
Standard Test Method of Tensile Properties
of Geotextiles by the Wide-Width Strip
Method
Standard Test Method for Deterioration
of Geotextiles from Exposure to Ultraviolet Light and Water (Xenon-Arc
Type Apparatus)
Test Method for Determining Inherent
Viscosity of Poly(Ethylene Terephthalate)
(PET) by Glass Capillary Viscometer
19
FHWA NHI-00-043
Mechanically Stabilized Earth Walls and
Reinforced Soil Slopes Design and
Construction Guidelines (Demonstration
Project 82)
FHWA NHI-00-044
Corrosion/Degradation of Soil
Reinforcements for Mechanically
Stabilized Earth Walls and Reinforced
Soil Slopes
D. U.S. Environmental Protection Agency
(U.S. EPA)
EPA 9090
Compatibility Test for Wastes and
Membrane Liners
E. U.S. Army Corps of Engineers (USACE)
Draft Specification for Grid Aperture
Stability by In-Plane Rotation
7.1.3 Definitions
Structural Geogrid - A structural geogrid is
formed by a regular network of integrally
connected tensile elements with apertures of
sufficient size to allow interlocking with
surrounding soil, rock, or earth and function
primarily as reinforcement.
7.1.4 Submittals
A. The Contractor shall submit 6 sets of detailed
design calculations, construction drawings,
and shop drawings for approval at least 30
days prior to the beginning of construction.
The calculations and drawings shall be
prepared and sealed by a Professional
Engineer, licensed in the State. Upon approval,
the Engineer will make available 2 sets of the
drawings to the Contractor. The Contractor
shall obtain the approved drawings prior to
commencing construction.
B. Submit geogrid product samples approximately
4 in. x 7 in. or larger and consisting of at least
4 entire apertures.
C. Submit Manufacturer’s installation instructions
and general recommendations.
7.1.5 Quality Assurance
A. Qualifications - The Engineer’s approval of
the system and the supplier will be based
upon the following considerations:
1. The geogrid reinforcement has been
reviewed and approved for use.
2. The supplier has a large enough operation
and the necessary experience to supply and
support the construction on a timely basis.
3. Past experience in the design and construction
of at least 10 projects of a similar magnitude
of the proposed system can be documented.
C. Pre-Construction Conference - Prior to the
installation of the geogrid, the Contractor
shall arrange a meeting at the site with the
geogrid material supplier and, where applicable,
the geogrid installer. The Owner and the
Engineer shall be notified at least 3 days in
advance of the time of the meeting. The
representative of the geogrid supplier shall be
available on an “as-needed” basis during
construction.
7.1.6 Delivery, Storage & Handling
Storage and Protection
A. Prevent excessive mud, wet concrete,
epoxy, or other deleterious materials from
coming in contact with and affixing to the
geogrid materials.
B. Store at temperatures above -20° F (-29° C).
C. Rolled materials may be laid flat or stood
on end.
7.2 PRODUCTS
7.2.1 Manufacturers
## VERIFY SECTION NUMBERS AND TITLES
A. Acceptable Suppliers - A supplier or their
representative must request, in writing 60
days prior to the bid date, to be placed on the
approved supplier list. An approved source is
The Tensar Corporation, Morrow, GA or their
designated representative.
B. Substitutions - See Section 01600 and sub-part
7.1.1.2 of this Section.
7.2.2 Materials
THE PLANS SHOULD INDICATE WHERE GEOGRID
TYPE(S) IS/ARE TO BE USED.
7.2.2.1 Structural Geogrid
The required physical and mechanical properties of
geogrid reinforcement shall be as shown on the
plans or established in writing by the Engineer at
least 30 days prior to the bid.
B. The design shall be signed by a registered
Professional Engineer who shall demonstrate
a minimum Errors and Omissions insurance
coverage of $1,000,000 by furnishing the
Engineer with a current certificate of insurance.
20
A. Primary Geogrid - The primary geogrid,
identified as types P1, P2, P3, and P4 shall
provide the following allowable tensile
properties:
*The tensile strength at 2 percent and 5 percent strain shall be
determined with this test conducted without artificially deforming
test materials under load before measuring such resistance or
employing an artificial secant or offset tangent basis of measurement
so as to overstate tensile properties.
**Where:
Ta =
TULT
RFCR x RFID x RFD
1. TULT - Ultimate Tensile Strength shall be the
minimum average roll value ultimate
tensile strength as tested per ASTM D6637.
This test shall be conducted without
artificially deforming test materials under
load before measuring such resistance or
employing an artificial secant or offset
tangent basis of measurement so as to over
state tensile properties.
2. RFCR - The Reduction Factor for Creep is the
ratio of TULT divided by the creep-limited
strength determined in accordance with
ASTM D5262-97. Long-term tensile-straintime behavior of the reinforcement shall be
determined from controlled laboratory testing
conducted for a minimum duration of 10,000
hours. The requirement for the minimum
creep test period may be waived for a new
product if it can be demonstrated that is
sufficiently similar to a proven 10,000 creep
tested product of a similar nature. When these
conditions are met, creep testing shall be
conducted for at least 1,000 hours and the
results compared to the similar product tested
for 10,000 hours. The 1,000-hour creep curves
must pattern very closely to the 1,000-hour
porting of the similar product to demonstrate
21
equivalency. Creep test data at a given
temperature may be extrapolated over time
by one order of magnitude. Accelerated
testing is required to extrapolate 10,000-hour
creep data to a 75-year design life. Procedures
for test acceleration are discussed in
GRI-GG4. Creep testing is required on
representative samples of the finished
product and not a single component of the
geogrid (e.g., fiber and/or yarn). The
ultimate strength used in this calculation
shall be that of the roll used in the testing and
not the MARV for the product. Creep rupture
testing, that has been performed through
the use of alternative techniques (e.g., stepped
Isothermal Method), must be supported with
creep data conducted for a minimum of
10,000 hours at 20 º C.
In no event shall the minimum value of
FSCR be less than:
PVC-coated PET geogrid
Acrylic-coated PET geogrid
HDPE uniaxial geogrid
PP biaxial geogrid
1.75
1.75
2.15
4.00
3. RFID - The Reduction Factor for Installation
Damage is the ratio of the virgin reinforcement
TULT divided by the TULT of a sample of the
same material recovered from an installation
damage test. Tests shall be conducted using
the actual backfill from the project in
accordance with GRI-GG4. However, in lieu
of such testing, the Manufacturer may
supply test results from other backfill soils
if such soils can be shown to result in more
severe construction damage than the
proposed backfill. TULT shall be determined
in accordance with ASTM D6637-01 and
sample recovery shall be consistent with
ASTM D5818-95.
4. RFD - Reduction Factor for Durability/Aging
is the combined partial factor for potential
chemical and biological degradation. RFD
shall be determined from polymer specific
(HDPE and PP as identified by their
mechanical properties, and PET as
identified by CEG number and number
average molecular weight, Mn) durability
testing covering the range of expected
soil environments. Polyolefin geogrids can
be used in a pH range from 2 to 12, and
polyester geogrids can be used within a
pH range of greater than 3 and less than 9.
The minimum Reduction Factor for
Durability/Aging for HDPE and PP shall
be 1.0. The minimum reduction factors
for PET geosynthetics are as follows:
B. Secondary Geogrid - The secondary
geogrid, identified as Types S1 and S2,
shall meet the following physical
property requirements:
Reinforced & Retained Fill
Product
3 < pH = 5
5 < pH < 8
8 = pH < 9
Polyester geogrids
2.0
1.6
2.0
Mn < 20,000; 40 < CEG < 50
Polyester geogrids
1.3
1.15
1.3
Mn > 25,000; CEG < 30
5. For soils of potential concern, as presented
below (modified soils shall include lime
stabilized soil, cement stabilized soil, or
concrete), only polymers listed as “no
effect” shall be used within or adjacent
to (3 feet shortest measurable distance)
these soil environments (Ref: Table 8,
FHWA NHI-00-044).
Soil Environment
Acid Sulfate Soils
Organic Soils
Saline Soils, pH < 9
Calcareous Soils
Modified Soils/Lime, Cement
Alkaline Soils, pH > 9
Acidic Soils, pH > 3
Soils with Transition Metals
PETP
NE
NE
NE
?
?
?
?
NE
PE
NE
NE
NE
NE
NE
NE
NE
?
PP
?
NE
NE
NE
NE
NE
NE
?
NE = No Effect
? = Questionable use, exposure tests required
6. Ci - Soil Interaction Coefficient value shall
be determined from long-term effective
stress pullout tests per GRI-GG5, unless the
junction creep testing of the geogrid is used
to determine Ta. The Ci value is determined
as follows:
Ci =
F
2 L N tan Where:
F = Pullout force (lbs/ft), per GRI-GG5
L = Geogrid Embedment Length in Test (ft)
N = Effective Normal Stress (psf)
= Effective Soil Friction Angle, Degrees
Unless noted otherwise, values shown are for the cross machine direction and represent
minimum average roll values with the exception that Flexural Stiffness, which is determined
in the machine direction and represents typical values. The tensile strength at 2 percent and
5 percent strain shall be determined with this test conducted without artificially deforming
test materials under load before measuring such resistance or employing an artificial secant
or offset tangent basis of measurement so as to overstate tensile properties.
* Bending resistance values determined in the machine direction using specimen dimensions
of 864 millimeters in length by 1 aperture in width.
**Resistance to in-plane rotation movement measured by applying a 20 kg-cm moment to
the central junction of a 9-inch by 9-inch specimen restrained at its perimeter and measured
in units of kg-cm/deg.
7.2.2.2 Geosynthetic Drainage Composite
A. The drainage composite shall consist of
geotextile bonded to both sides of a polyethylene
net structure. Drainage products manufactured
with a cuspated core shall not be acceptable.
B. The minimum allowable transmissivity as
per ASTM D4716-95 shall be equal to or
greater than 1.5 gal. per min. per ft. of width
at a confining pressure of 10,000 lbs. per sq. ft.
for a gradient of 1.0.
C. The minimum allowable peel strength of
the geotextile from the geonet as per ASTM
F904-91 shall be equal to or greater than 250
gm. per in. of width.
7.2.2.3 Erosion Control System
A. The erosion control system shall consist of a
combination of long-term nondegradable
TRM, geogrid, SierraScape facing element,
and/or geotextile.
B. The erosion control system can vary based
on soil types, slope angle, climate, and
vegetation requirements. Supplier shall provide
specific erosion control system design for
approval by Agency on a job-by-job basis.
22
the load/deformation characteristics of the
overlap of geogrid materials is equal to or
exceeds those of the geogrid. The minimum
overlap shall be 5 feet.
7.3 Execution
7.3.1 Examination
The Contractor shall check the geogrid upon
delivery to verify that the proper material has
been received. The geogrid shall be inspected
by the Contractor to be free of flaws or damage
occurring during manufacturing, shipping, or
handling.
7.3.4 Fill Placement Over the Geogrid
## VERIFY SECTION NUMBERS AND TITLES
7.3.2 Preparation
The subgrade soil shall be prepared as indicated
on the construction drawings or as directed by the
Engineer. Foundation soil shall be excavated to
the lines and grades as shown on the drawings or
as directed by the Engineer. Overexcavated areas
shall be filled with compacted backfill material.
7.3.3 Installation
A. Geogrid shall be laid at the proper elevation
and orientation as shown on the construction
drawings or as directed by the Engineer.
Where percent coverage and truncation
options are shown on the plans, alternate
layers of primary UX Geogrid reinforcement
shall be placed in a staggered pattern such
that the layer above is placed with the center
line of the geogrid in alignment with the
centerline of the open space below. The
maximum horizontal spacing between
geogrids where percent coverage design
alternates are employed shall be 4 to 6 inches.
Correct orientation (roll direction) of the
geogrid shall be verified by the Contractor.
Geogrid may be temporarily secured in place
with staples, pins, sand bags, or backfill as
required by fill properties, fill placement
procedures, or weather conditions, or as
directed by the Engineer.
B. Geogrid soil reinforcement shall be
connected/spliced when required to provide
continuity of tensile resistance. Geogrids
manufactured using polyolefins (e.g., HDPE
and PP) shall be connected with a mechanical
polymer bar. Geogrids manufactured of
polyester shall be connected by sewing
with Kevlar sewing thread perpendicular
to the direction of loading at the ends of
the materials.
C. Overlap connections may be used if the
Contractor provides the Engineer independent
test documentation which demonstrates that
23
A. Backfill material shall be placed in lifts and
compacted as directed under Section 02300.
Backfill shall be placed, spread, and
compacted in such a manner that minimizes
the development of wrinkles in and/or
movement of the geogrid.
B. Tracked construction equipment shall not be
operated directly on the geogrid. A minimum
fill thickness of 6 inches is required prior to
operation of tracked vehicles over the geogrid.
Turning of tracked vehicles should be kept to
a minimum to prevent tracks from displacing
the fill and damaging the geogrid. Rubbertired equipment may pass at slow speeds
(less than 10 mph) over extruded polyolefin
geogrid reinforcement placed atop competent
substrate. Sudden braking and sharp turning
shall be avoided. Rubber-tired equipment
shall not pass over polyester geogrid
reinforcement. A minimum fill thickness of
6 inches is required prior to operation of
rubber-tired equipment over polyester
geogrid reinforcement.
7.3.5 Repair
A. Any geogrid damaged during installation
shall be replaced by the Contractor at no
additional cost to the Owner.
B. Coated geogrids shall not be used if the
coating is torn, shedding, cracked, punctured,
flawed or cut, unless a repair procedure is
carried out as approved by the Engineer. The
repair procedure shall include placing a
suitable patch over the defective area or
applying a coating solution identical to the
original coating.
7.3.6 Protection
Follow the Manufacturer’s recommendations
regarding protection from exposure to sunlight.
8.0 SIERRA INSTALLATION GUIDE
Step 1 – Site Excavation. The site should be
properly excavated to the lines and grades as
shown on the construction drawings or as
directed by the Engineer. Excavation should
include removal of soil to ensure firm foundation
and benching the back cut into competent soils to
improve stability.
Step 2 – Internal Drainage. Drainage
composite shall be rolled out onto the benched
back cut prior to installation of geogrid and fill
placement. Roll drainage composite up the back
cut until approximately 2/3 of the reinforced
slope height is reached. Drainage composite is
typically placed to achieve 30% coverage unless
design considerations dictate otherwise. The
drainage composite is normally terminated
against a slotted drain pipe within geotextile
wrapped gravel (See Figure 8.1).
Step 3 – Geogrid Lengths and Types. Two types
of Tensar structural geogrids are used in Sierra
Slopes: Uniaxial (UX) and Biaxial (BX). These
terms refer to the number of directions in which a
punched sheet of polymer has been drawn in the
manufacturing process. Uniaxial has one direction
of draw and biaxial has two. (Figure 8.2)
Figure 8.1 — Benching the Backcut
Figure 8.2 — Types of Tensar Geogrid
For construction using Tensar UX Geogrids, the
longitudinal roll direction must be oriented
perpendicular to the slope face. In construction
using Tensar BX Geogrids, the transverse roll
direction is typically oriented perpendicular to the
slope face. A simple check of Tensar UX Geogrid
orientation is to ensure that the longer of the two
geogrid aperture axes is perpendicular to the slope
face alignment.
Primary reinforcement lengths are typically longer
than secondary reinforcement lengths and may
vary with location and elevation. Generally,
secondary reinforcement length is the same
throughout the slope.
Simple procedures can minimize the potential
installation of incorrect geogrid lengths. For
construction expedience, the geogrid reinforcement
is often cut to length in a staging area. These cut
lengths are then stockpiled and marked or tagged
to indicate their length.
24
A potential problem can arise on projects where
two different geogrids are utilized. For instance,
different grades of Tensar UX Geogrids may look
very much alike. Confusion between different
structural geogrids can be eliminated by proper
separation during stockpiling, precutting, and
tagging operations. The geogrids may also be
color coded with spray paint.
Step 4 – Geogrid Placement. Geogrid layers
should extend back from the slope face to the
distance specified and placed at the elevations
shown on the construction drawings. (Figure 8.3)
Adjacent geogrid strips should be butted together
side-by-side without overlap (Note: A small overlap
may be specified for wrap-around construction of
the slope face). Some designs may call for partial
coverage requiring a space between geogrid strips.
Soil is usually piled on the ends of the strips or use
of “U” shaped ground anchors to avoid movement
of the geogrids during fill placement.
Figure 8.3 — Placing Geogrid Strips
Care must be taken to prevent slack from becoming
trapped within the geogrid as fill is placed. Tracked
construction equipment must not be operated
directly upon the geogrid. Rubber-tired equipment
may pass over the geogrid at slow speeds. Sudden
braking and sharp turning that can displace
geogrids from their intended positions should
be avoided.
Overlapping geogrids on convex curves of slope
alignments should be separated by at least three
inches of compacted slope fill. Geogrids on
concave curves may simply diverge from the
slope face as shown in Figure 8.4.
Figure 8.4 — Placing Geogrid on Curves
Step 5 – Common Fill and Topsoil Fill Placement.
Fill can be placed and spread directly upon the
geogrids. Compact the soil to specifications using
standard equipment and procedures (Figure 8.5
and 8.6). Lift thickness should be great enough to
ensure that sheepsfoot will not come in direct
contact with the geogrid.
Topsoil is typically placed up to a depth 1–2 feet
back from the slope face during the fill placement
process. This insures that an adequate layer of
topsoil is in place to support vegetation and be
reinforced by the geogrid reinforcement.
Figure 8.5 — Placing Fill
25
Figure 8.6 — Compaction
Figure 8.7 — Burial of Transverse Terminal Ends (6” x 12”)
During construction, soil may cascade over the
slope edge and begin to pile up on the slope face.
This soil should be removed to insure a consistent
grade is maintained. Failure to remove this soil
will result in localized sliding of the slope face.
Typically, the slope face will be overbuilt 2–4 feet
to achieve adequate compaction. The slope face
can be cut back to final grade by the use of a back
hoe with a smooth bucket. Care should be taken
to insure that grid layers are exposed at the face of
the slope indicating that geogrid reinforcement
extends completely to the slope face.
erosion control measures during and shortly after
construction must be taken to ensure proper
establishment. Water must be prevented from
overtopping the slope crest and forming erosion
ruts in the face of the slope. Design considerations
must be taken to pipe or channel water away to
the toe of the slope.
The final treatment of the slope face may require
compaction to create a relatively smooth surface
to ensure adequate performance of the erosion
control system.
Step 6 – Erosion Control System. The erosion
control system is often constructed at the completion
of the slope after all other construction is completed.
This method is usually limited to slopes that are 45°
or flatter and do not require a wrap technique.
Placement of a long-term non-degradable erosion
blanket can be done quickly and easily with a
minimum of hand labor. Beginning at the crest
of the slope bury the transverse terminal end of the
blanket to secure and prevent erosive water flow
underneath (Figure 8.7). Unroll blanket from top of
the slope face and secure with 8 in. - 12 in. “U” shape
metal staples. Blanket should lay flat. DO NOT
PULL BLANKET TAUT. Pulling taut may cause
blanket to bridge depressions in the surface and
allow erosion underneath. Refer to Manufacturer’s
Installation Guidelines for specific details. Temporary
Wrapped Face System. Slopes steeper than 45°,
landscaped slopes, and rock faced slopes will
typically require a wrapped face system.
SierraScape facing elements should typically be
used for this purpose. TET’s SierraScape System
provides superior protection against surficial
slope failure during and immediately following
construction where vegetation is being established.
In addition, SierraScape facing elements serve as
forming devices to ensure a consistent slope angle
and enhance compaction at the face. A typical
wrapped-face system is shown in Figure 8.8.
Other techniques using welded wire or boards
may be used. Consult your manufacturer
representative for details on these systems.
TENSAR GEOGRID
SIERRASCAPE
FACING ELEMENT
GEOTEXTILE
SUPPORT STRUT
REINFORCED
FILL
TENSAR GEOGRID (PRIMARY REINFORCEMENT)
SIERRASCAPE CONNECTION
Figure 8.8 SierraScape System Detail
26
Step 7 - Vegetation Installation. The landscape
design of a Sierra Slope will specify details on
vegetation choices and installation. Common
methods used for establishment of grass or wildflowers are to hydroseed, dry spread seed, or sod.
Seed or sod is placed by these techniques on the
prepared soil of the slope face and held in place
by geogrids or long-term non-degradable erosion
mattings. Landscaped or revegetated native slopes
will typically require the use of containerized,
balled and burlap, or bare root plantings. Planting
holes are usually dug by hand using hand tools or
hand-held mechanical augers. Care must be taken
to ensure worker safety by the use of safety lines,
ladders, and proper supervision.
■
Mowing Operation Dont’s
■ Mow too often. This wastes money, exposes
mowing crews to traffic hazards more than
needed, and can damage the vegetation.
■
Mow at the wrong time. Good timing reduces
the frequency of mowing required by cutting
the vegetation in the right stage of growth.
■
Mow too short. Leaving the proper height helps
maintain the stand of vegetation and keeps
small litter objects hidden.
■
Mow steep slopes if you don’t need to. Steep
slope operations increase risk of mower
accidents.
■
Mow patterns inconsistently and mow a regular
area incompletely. Drivers watch the pattern of
a mowed area to help understand the safety of
an area. Consistent mowing of similar areas
helps drivers evaluate the safety of the roadway.
■
Mow when wet. This is hard on equipment.
■
Operate equipment carelessly and scar trees
and shrubs. Mowing is tedious but care must
be taken to avoid accidents and preserve
valuable plantings.
9.0 MAINTENANCE & MOWING
Maintain slopes in accordance with owners
specifications. Additional guidelines for mowing
do’s and don’ts are as follows45:
Mowing Operation Do’s
■ Avoid mowing slopes steeper than 2.5:1 with
a regular mower unit.
■
Mow slopes steeper than 2.5:1 with side
mounted mower on a boom if the tractor unit
remains on flatter surfaces while mowing.
■
Operate side-mounted or boom mower units
on the uphill side of the tractor to limit the
possibility of overturning the tractor.
■
Replace broken or lost chain guards to deflect
debris immediately. Using flail-type mowers
reduces the amount of debris thrown.
■
Cover all v-belts, drive chains, and power
takeoff shafts.
■
Raise mowers when crossing driveways
or roadways.
■
Shut off power before checking any mower
unit. Block a mower before changing, sharpening,
or replacing a blade. Any blade being re-installed
should be checked for cracks or damage that
will lead to failure.
■
Using flashing signals and slow-moving-vehicle
signs on all mower tractors.
27
Use signs to warn traffic, such as “Mowing
Ahead, Mowing Area, Road Work Ahead” or
similar legends. Signs should not be more than
one to two miles ahead of the mowing. Signs
saying “Mowing Next __ Miles” may be used in
advance of the operation, but the distance limits
should not be shorter than two miles nor longer
than five miles.
APPENDIX A
REINFORCED FILL SOIL
PARAMETERS
A.1 Gradation, Plasticity Index, and
Chemical Composition
Gradation9: Recommended backfill requirements
for MSE slopes per FHWA4 are:
Sieve Size
4 inch
No. 4
No. 40
No. 200
Percent Passing
100-75
100-20
0-60
0-50
Definition of total and effective stress shear
strength properties become more important as
percent passing the No. 200 sieve increases.
Likewise, drainage and filtration design are
more critical.
Plasticity Index9. PI 20 (AASHTO T-90) and a
magnesium sulfate soundness loss < 30% after 4
cycles is required.
Note that fill materials outside of these
graduation and plasticity index requirements
have been used successfully9,44. Performance
monitoring is recommended if fill soils fall
outside of the requirements listed above.
Chemical Composition. The chemical
composition of the fill and retained soils should be
assessed for affect on durability of reinforcement
(pH, chlorides, oxidation agents, etc.). Soils with
pH > 12 or with pH 3 should not be used
in Sierra Slopes12. A pH range 3 to 9 is
recommended. Specific supporting data should
be required if pH > 9.
For all other soils, peak effective stress and total
stress strength parameters should be determined.
These parameters should be used in the analysis
to check stability immediately after construction
and long-term. Use consolidated drained (CD)
direct shear tests (sheared slowly enough for
adequate sample drainage) or consolidatedundrained (CU) triaxial tests with pore water
pressures measured for determination of total
stress parameters.
It is recommended that shear strength testing be
conducted. However, use of assumed shear values
based on agency guidelines and experience may
be acceptable for some projects. Verification of site
soil type(s) should be made after excavation is
made or borrow pit identified, as applicable.
Unit Weights. Dry unit weight for compaction
control, moist unit weight for analysis, and
saturated unit weight for analysis (where
applicable) should be determined for the fill soil.
A.3 Topsoil
Successful vegetation establishment and survival
is a key component in the long-term design of
an MSE slope. Consequently, based on local
conditions, placement of a topsoil may be
required. Topsoil qualities can vary widely but
typically a topsoil fill classified in the AASHTO
A-2-6 to A-2-7 ranges can be used. A minimum of
2% organic matter is also valuable to successfully
support plant life.
A.2 Soil Fill Design Properties
Shear Strength. Peak shear strength parameters
should be used in the analysis8. Effective stress
strength parameters (,c) should be used for
granular soils with less than 15% passing the
No. 200 sieve. Parameters should be determined
using direct shear or consolidated-drained (CD)
triaxial tests.
28
APPENDIX B
VEGETATION AND EROSION
CONTROL SYSTEM
SELECTION GUIDELINES
B.1 Vegetation Facing Selection
B.2 Erosion Control System Selection
A key feature of the Sierra System is the flexibility
it offers the designer to create an attractive
and natural facing. Selection of the vegetation
component is an integral part of the overall design
of the erosion control system. Vegetation should
be selected to blend with or accent existing site
conditions. Slope angle should also be
considered when the vegetation selection is made.
There are four primary types of vegetation facings
available. Table B.1 below describes these options
and typical sites where they can be used.
After the desired slope angle and vegetation
selection are made an erosion control system can
be designed. The typical erosion control system
will employ a biotechnical design. Engineering
design techniques and horticulture experience
are used to combine geosynthetic materials and
vegetation to create a stable slope facing system.
These options can be divided into three groups
based on slope angle. Table B.2 on the following
page describes the most common erosion control
products and vegetation options used on
Sierra Slopes.
Table B.1
Recommended Maximum Slope Angle and Typical Sites
For Vegetation used on Sierra Slopes
Type of Vegetative Facing
Slope Angle
Grass or Crown VetchApplied by hydroseeding or
rotary spreaders and used in
conjunction with an erosion
control mat or blanket.
1/2:1 or flatter
WildflowerApplied by hydroseeding or
rotary spreaders and used in
conjunction with an erosion
control mat or blanket.
1:1 or flatter
Landscaped SlopeA designed ornamental planting
using selected shrubs and
ground covers in a mulched bed.
The plants are generally hand
planted with a landscape fabric
employed to control erosion and
reduce weed infiltration.
Native PlantingA revegetated slope that
combines naturally occurring
ground cover, grasses, shrubs,
and trees. Usually combines
both seeding and hand planting
techniques.
1:1 or flatter
1:1 or flatter
29
Recommended Typical Site
- Downslope roadway
embankment
- Backside or low visibility side
of development
- Rural site
-
Upslope roadway embankment
Native landscape setting
Suburban setting
Rural site
- Urban or suburban road
widening
- Property entrance or frontage
- Homeowners slope
-
Native rural landscape
Wetlands site
Arid mountain side
Reforested area
Table B.2
Erosion Control System Selection Guidelines
Slope Angles
Vegetation1
Erosion Control System
Description
1:5:1
Flatter
Grass, crown
vetch or
wildflower mix
Excelsior Blanket
Straw Blanket
Geosynthetic Erosion Blanket
Landscape slope
planted shrubs in
mulched bed
Geotextile wrapped face2
Native planting
seeded native grasses,
ground covers, and
planted shrubs or trees
Excelsior Blanket
Geosynthetic Erosion Blanket
Grass crown vetch or
wildflower mix
Geosynthetic Erosion Blanket
Landscaped slope
with planted shrubs
in mulched bed
Geosynthetic wrapped face2
Native planting
using seeded
native grasses,
ground covers,
and planted shrubs
or trees
Geosynthetic Erosion Blanket
Grass
sod held by
geogrid wrap
Tensar BX Geogrid wrapped
face with wire forms
Grass and crown vetch
seeded mix
Geotextile and geogrid
wrapped face with wire forms
Grass
seeded mix applied
through erosion blanket
Geosynthetic Erosion Blanket
and Tensar BX Geogrid wrap
with wire forms
1:1 - 1:5:1
1/2:1 – 1:1
1. General recommendations on vegetation options are outlined in Sierra Slope Facing Selection Manual.
2. Use a professional grade landscape fabric or 6 oz. (min.) needle-punched nonwoven geotextile.
30
REFERENCES
11
Seed, H.B. and Whitman, R.V., “Design of Earth
Retaining Structures for Dynamic Loads, Lateral
Stresses in the Ground and Design of EarthRetaining Structures,” Cornell University, June
22-24, 1970, American Society of Civil Engineers,
New York, pp. 103-147.
1
Wrigley, N.E., “The Durability and Aging
of Geogrids” Symposium on Durability and
Aging, Geosynthetic Research Institute, Drexel
University, Philadelphia, December, 1988.
2
Wrigley, N.E., “Durability and Long-Term
Performance of ‘TENSAR’ Polymer Grids for
Soil Reinforcement,” Materials Science and
Technology, Vol 3, 1987, pp. 161-170.
12
“Design Guidelines for Use of Extensible
Reinforcements (Geosynthetic) for Mechanically
Stabilized Earth Walls in Permanent Applications,”
Task Force 27 Report, In Situ Soil Improvement
Techniques, AASHTO, Washington D.C.,
August 1990.
3
Quality Manual for the Manufacture of Tensar
Geogrids, The Tensar Corporation, Morrow,
Georgia, October, 2002.
13 Collin, J.G. and Berg, R.R., “Comparison of
Short-Term and Long-Term Pullout Testing of
Geogrid Reinforcements,” Geosynthetic Soil
Reinforcement Testing Procedures, ASTM STP
1190, S.G. Jonathan, Cheng, Ed., American Society
of Testing & Materials, Philadelphia, 1993.
4
FHWA NHI-00-043, “Mechanically
Stabilized Earth Walls and Reinforced Soil Slopes
Design and Construction Guidelines”, U.S.
Department of Transportation, Federal Highway
Administration, 2001.
5
GRI Test Method GG5, “Geogrid Pullout,”
Geosynthetic Research Institute, Drexel
University, Philadelphia, January 30, 1991.
14
Terzaghi, K. and Peck, R.B., “Soil Mechanics in
Engineering Practice,” Second Edition, John Wiley
and Sons, New York, 1967.
6
Mitchell, J.K. and Villet, W.C.B., “Reinforcement
of Earth Slopes and Embankments,” NCHRP
Report No. 290, Transportation Research Board,
Washington, D.C., 1987.
7 Bonaparte,
R., and Berg, R.R., “LongTerm Allowable Tension for Geosynthetic
Reinforcement,” Proceedings of Geosynthetics
‘87 Conference, Vol. 1, New Orleans, February,
1987, pp. 181-192.
15 Campbell, “Soil Slips, Debris Flows and
Rainstorms in the Santa Monica Mountains,
Southern California,” U.S. Geological Survey
Professional Paper 851, 1975.
16
Thielen, D.L. and Collin, J.G., “Geogrid
Reinforcement for Surficial Stability of Slopes,”
Proceedings of Geosynthetics ‘93 Conference,
Vancouver, B.C., March, 1993.
8 Berg,
R.R., Chouery-Curtis, V.E., and Watson,
C.H., “Critical Failure Planes in Analysis of
Reinforced Slopes,” Proceedings of Geosynthetics
‘89 Conference, Vol. 1, San Diego, February, 1989.
9
Christopher, B.R., Gill, S.A. Giroud, J.P., Mitchell,
J.K. Schlosser, F. and Dunnicliff, J., “Reinforced
Soil Structures, Volume 1: Design and Construction
Guidelines,” FHWA-RD-89-043.
10
Bonaparte, R., Schmertmann, G.R., and
Williams, N.D., “Seismic Design of Slopes
Reinforced with Geogrids and Geotextiles,
Proceedings of the Third International Conference
on Geotextiles, Vienna, Austria, 1986, pp. 273-278.
31
17
GRI Test Method GG4a and GG4b,
“Determination of Long-Term Design Strength
of Geogrids,” Geosynthetic Research Institute,
Drexel University, Philadelphia, March 26, 1990.
18
ASTM Test Method D4759, “Standard Practice
for Determining the Specification Conformance of
Geosynthetics,” American Society for Testing and
Materials, Philadelphia, 1988.
19 GRI Test Method GG1, “Geogrid Rib Tensile
Strength,” Geosynthetic Research Institute, Drexel
University, Philadelphia, January, 1988.
20
ASTM Test Method D5262, “Tension Creep
Testing of Geogrids, “ American Society for
Testing and Materials, Philadelphia, 1988.
21
Yeo, K.C., Thesis presented in partial fulfillment
of the PhD, University of Strathclyde, Scotland,
1985.
22
McGown, A., Andrawes, K.Z., Yeo, K.C. and
DuBois, D., “The Load-Strain-Time Behavior of
Tensar Geogrids,” Polymer Grid Reinforcement
Conference, Science and Engineering Research
Council, Thomas Telford Ltd., London, 1984.
23
30
Dorrosion/Degradation of Soil Reinforcements
for Mechanically Stabilized Earth Walls
Reinforced Soil Slopes,” FHWA-SA-96-072, U.S.
Department of Transportation Federal Highway
Administration, Washington, D.C., 1997.
31
Environmental Protection Agency (U.S. EPA),
“Compatabilty Test for Wastes and Membrane
Liners, “ Method 9090, Washington, D.C., 1985.
32
American Society of Civil Engineers, Structural
Plastics Selection Manual, ASCE Manuals and
Reports on Engineering Practice No. 66, prepared
by Task Committee on Properties of Selected
Plastic Systems of the Structural Plastic Research
Council of the Technical Council on Research of
ASCE, New York, 1985, p 584.
Tensar Technical Note: PT 2.0 - “The Chemical
Resistance of Polyethylene and Polypropylene
Polyolefins,” The Tensar Corporation, Morrow,
Georgia, 1986.
24
34
Bush, D.I., “Variation of Long-Term Design
Strength of Geosynthetics in Temperatures Up
to 40° C,” Proceedings of the 4th International
Conference on Geotextiles,” Geomembranes,
and Related Products, The Hague, Netherlands,
May, 1990.
25
ASTM Test Method D 2837, “Obtaining
Hydrostatic Design Basis for Thermoplastic Pipe
Materials,“ American Society for Testing and
Materials, Philadelphia, 1990.
26
Communication from Donald E. Duvall, Vice
President, Plastics Technology, L.J. Broutman &
Associates, Ltd., Chicago, January 31, 1992.
27
Bush, D.I. and Swan, D.B.G., “An Assessment
of the Resistance of Tensar SR2 to Physical
Damage During the Construction and Testing of
a Reinforced Soil Wall,“ The Application of
Polymeric Reinforcement in Soil Retaining
Structures, NATO ASI Series, Kluwer Academic
Publishers, Norwell, MA, 1988.
28
Bush, D.I., “Evaluation of the Effects of
Construction Activities on the Physical Properties
of Polymeric Soil Reinforcing Elements,“
International Geotechnical Symposium on Theory
and Practice of Earth Reinforcement, Fukuoka,
Japan, October, 1988.
29
Rainey, T. and Barksdale, R., “Construction
Induced Reduction in Tensile Strength of Polymer
Geogrids.” Proceedings of Geosynthetic ‘93
Conference, Vancouver, B.C., March, 1993.
33
Elias, V. “Allowable Loads for Geosynthetics
in Structural Designs.” Unpublished. 1993.
Shelton, W.S. and Wrigley, N.E. “Long-Term,
Durability of Geosynthetic Soil Reinforcement,”
Proceedings of Geosynthetics ‘87 Conference,
New Orleans, LA, 1987.
35
Albertsson, A-C, “Biodegradation of Synthetic
Polymers, II - A Limited Microbial Conversation
of 14C in Polyethylene to 14C02 by some Soil
Fungi,” Journal of Applied Polymer Science,
Vol 22, 1987.
36
Albertsson, A-C, Banhidi, Z.G., and BeyerEricsson, L-L, “Biodegradation of Synthetic
Polymers, III - The Liberation of 14C02 by Molds
Like ‘Fusarium Redolens’ from 14C Labeled Pulverized High-Density Polyethylene,” Journal of
Applied Polymer Science, Vol 22, 1978.
37
Albertsson, A-C and Banhidi, Z.G., “Microbial
and Oxidative Effects in Degradation of
Polyethylene,” Journal of Applied Polymer
Science, Vol 25, 1980.
38
ICI Petrochemicals and Plastics Division, “The
Stability and Chemical Resistance of ‘Propathene’,”
Technical Report TS/P/A/14/86, Wilton,
England, 1986.
39
Allen, T.M., “Determination of Long-Term
Tensile Strength of Geosynthetics: A State of the
Art Review,” Proceedings of Geosynthetics ‘91,
Atlanta, GA, February, 1991.
40
Proceedings of the 3rd GRI Seminar on the
topic of THE SEAMING OF GEOSYNTHETICS,
Geosynthetic Research Institute, Drexel
University, Philadelphia, December, 1989.
32
41
Bush, D.I., Joining Tensar SR55, SR80, AND
SR110 Geogrids, Nelton Ltd., Blackburn, England,
December, 1988.
42
Wrigley, N.E., “The Failure Mode of ‘Tensar’
High Density Polyethylene Geogrids:
Performance of Reinforced Soil Structures,” Ed:
McGown, Yeo & Andrawes, Thomas Telford,
London, T 4/1, 371-372.
43
Wrigley, N.E. and Collin, J.G., “Time-StrainStress-Rupture Performance of Oriented HDPE
Geogrids,” Unpublished, 1993.
44
Hayden, R.F., Schmertmann, G.R., Qedan,
B.Q., and McGuire, M.S. “High Clay Embankment
Over Cannon Creek Constructed with Geogrid
Reinforcement,” Proceedings of Geosynthetics ‘91,
Atlanta, GA, February, 1991.
45
Country Roads & City Streets. Vol. 18, No. 1,
March 2003, page 4.
For more information, contact:
®
Tensar Earth
Technologies, Inc.
5883 Glenridge Drive, Suite 200
Atlanta, Georgia 30328
800-TENSAR-1
www.tensarcorp.com
1.800.667.4811
nilex.com
© 2003, Tensar Earth Technologies, Inc. TENSAR and SIERRA are registered trademarks. Certain foreign trademark rights also exist. The information contained herein has been carefully compiled by Tensar Earth Technologies, Inc. and to the best of its knowledge accurately represents Tensar
product use in the applications which are illustrated. Final determination of the suitability of any information or material for the use contemplated and
its manner of use is the sole responsibility of the user. Printed in the U.S.A.
TTN-Sierra-7.03
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement