Soil-Water Characteristic Curve

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Fredlund SWCC Device
 In situ overburden pressure can be applied
during the test
The Fredlund SWCC Device is a simple unsaturated
soil testing apparatus with great flexibility for applying
matric suctions while following various stress paths.
The device can be used to obtain the complete soilwater characteristic curve, SWCC, for a soil. This
device allows you to control matric suctions from near
zero values up to 1500 kPa (i.e., 15 bars), and is
capable of applying one-dimensional loading, Ko, to a
specimen with a diameter up to 71 mm. The device is
economically priced and is a complete ‘turn-key’
system constructed of stainless steel. SWCCs can be
performed on ‘as-compacted’, ‘initially slurried’, or
‘undisturbed’ specimens, starting with either dry or wet
conditions. The pore-air pressure, ua, at the top of the
specimen is controlled through the use of dual
pressure regulators and precise gauges.
 Compression (volume change) & water content
 Applied suctions up to 1,500 kPa
 Both drying (desorption) and wetting
(adsorption) pressures can be measured
 Dual pressure gauges and regulators for
precise pressure control
 Null-type initial suction measurements using
axis-translation technique
 Flushing ability and measurement of diffused
 Pressure compensator on the loading ram
 Complete documentation and testing guide
6103 S. Maple Av. Tempe AZ 85283 U.S.A.
The stainless steel cell is constructed with simple
knobs and screws for fast soil specimen setups. The
Tel: (480) 456-0110
device includes a pressure panel with dual gauges and
regulators for increased precision in the low-pressure
range. The apparatus also includes the necessary
plumbing and valves for periodic flushing and
measuring of diffused air. Several different high-airentry-value (HAEV) ceramic stones can be easily
interchanged. HAEV ceramic stones rated at 100, 300,
500, and 1500 kPa are available. The appropriate
ceramic stone can be selected depending on the soil
type being tested. During a test, the soil specimen can
either be subjected to a token vertical load, or a load
similar to the overburden pressure in the field. The in
situ overburden pressure can be applied with this
apparatus by simply adding dead weights to the weight
Miniature Heater
The application of a token pressure (e.g., 10 kPa) helps
provide a positive contact between the soil specimen
and the ceramic stone. The contact between the soil
and the ceramic stone is essential for efficient water
migration to and from the soil specimen. Alternatively,
larger normal pressures can be applied to the specimen
using a loading frame equipped with a pneumatic
loader, a pressure gauge, and an air regulator.
There is a pressure compensator on the vertical loading
ram. This means that the load applied to the specimen
is directly related to the applied load and there is no
tendency for the piston to move upward due to the air
pressure within the soil specimen chamber. This
design provides increased safety, particularly when
operating the device at high pressures. Water released
or absorbed by the soil specimen can be quantified
using the volume tube readings, which enables the
computation of water content at any given time. There
is no need to dismantle the apparatus after equilibrium
at each applied pressure increment, to determine the
water content. The apparatus allows the use of a single
soil specimen to obtain the entire SWCC with any
number of data points.
In addition, the volume change can be monitored by
measuring the change in sample height (provided the
soil specimen does not separate from the sides of the
steel ring). It is important to independently monitor total
Pneumatic Loading Frame & Hanging Colum
volume change and water content change when desiring
to compute the degree of saturation
throughout the test.
specimens with up to 71-mm in diameter and up to 50 mm in height.
The assembly includes load balance pressure compensator for uplift
forces on normal load piston.
The Fredlund SWCC device can be equipped with a
miniature heater and a control panel that can maintain
the chamber temperature constant and slightly above
ambient temperature.
This optional feature helps
prevent condensation of water vapor.
1.2) SWC–PCP Pressure Control Panel
Complete pressure control system for direct control of pore air
pressure, ua, at the top of the soil specimen with dual pressure
regulators and gauges for precise measurement and control of soil
suctions. 1,500 kPa high range and 200 kPa low range with manual
valve range selection and low range overload protection. Note: Option
3 should be used if the intended air supply is a nitrogen bottle.
Another optional feature available with the device is the
“hanging column” accessory, which enables the
application of low suctions to soil specimens. This
feature is illustrated in the schematic diagram shown
1.3) SWC–112-63 Specimen Cutting Ring
Stainless steel ring provided with the system for 63-mm diameter and
up to 25-mm high specimens. Other sizes (25, 38, 50, and 71 mm)
are available as options.
1.4) SWC–CSM-05 Mounted Ceramic Stone
5-bar HAEV ceramic stones mounted on stainless steel ring for quick
installation/removal. Provided with the system. 1, 3, and 15-bar
ceramic stones are available as options.
1.5) SWC-HCON Heat Control Accessory
Miniature heater for maintaining the chamber temperature slightly
above ambient temperature. This option helps prevent condensation
of water vapor inside the chamber.
2) SWC–FRM Pneumatic Loading Frame
Small 2-column standing load frame with stainless steel columns and
hard-anodized aluminum top and bottom plates. Includes doubleacting Bellofram diaphragm air cylinder with 10-kN capacity and 50mm stroke. Also includes pressure regulator and gage for manual
application/control of normal load.
SWCC Device with Hanging Column
If the available air compressor does not have enough
capacity, use of bottled nitrogen gas may be necessary
to apply suctions up to 1,500 kPa.
pressure regulators are available as an option to
minimize gas losses and to extend the life of the nitrogen
gas bottle.
As the name indicates, non-relieving
pressure regulators require an extra valve to relieve or
vent the pressure (chamber pressure is held even if the
regulator is turned down). This extra valve is included
with the non-relieving regulators option.
3) SWC–NAR Non-Relieving Air Regulators
The two standard air regulators on the pressure panel are replaced
with non-relieving air regulators when the pressure source is a
nitrogen bottle. This will eliminate unnecessary leakage of nitrogen.
However, when dismantling, the chamber pressure should be relieved
manually opening a vent, which is included with this option.
4) SWC–CSM Additional Mounted Ceramic Stones
SWC-CSM-01, SWC-CSM-03, SWC-CSM-05, and SWC-CSM-15.
HAEV ceramic stones rated 1, 3, 5, and 15-bar mounted on stainless
steel rings for quick installation and removal.
1) SWC–150 Fredlund SWCC Device
Unsaturated soil testing system used to obtain the complete soil-water
characteristic curve (SWCC) of any soil. The Fredlund SWCC Device
allows you to control suctions up to 15 bars and is capable of applying
one-dimensional loading to specimens with a diameter of up to 71 mm.
This device includes a pressure panel with dual gauges and regulators
for increased precision at low-pressure ranges and a miniature heater
to prevent water vapor condensation. It also includes the necessary
plumbing and valves to measure the diffused air. Several different
High-Air- Entry-Value (HAEV) ceramic stones are available and can be
easily interchanged. Normal loads can be applied to the specimen
using dead weights or, using a loading frame. Requires clean, dry
compressed air or nitrogen bottle.
1.1) SWC–PCA Pressure Cell Assembly
Stainless steel SWCC cell with a load piston to apply normal stresses
and/or measure specimen volume change.
Accommodates soil
Mounted and Unmounted Ceramic Disks
5) SWC–CSU Unmounted Ceramic Stones
SWC-CSU-01, SWC-CSU-03, SWC-CSU-05, and SWC-CSU-15.
Unmounted HAEV ceramic stones rated 1, 3, 5, and 15-bar with
holder rings. User is expected to mount the ceramic stones properly
using epoxy, and test the bubbling pressure prior to use.
12) SWC-BENDER SWC Platens with Bender Element sensors
Top and bottom SWC platens with bender element sensors for
measuring shear wave velocity in soil. Also includes 6 HAEV
ceramic disks rated for 1, 5, 10 or 15 bars (please specify at the time
of ordering).
6) SWC–107 Disk Holder Ring
Ceramic stones are mounted to disk holder rings using epoxy. This
option is required when ordering unmounted ceramic stones.
13) ULT-100 P & S Ultrasonic Velocity Measurement System
Ultrasonic Velocity test system for automatic measurements of P & S
wave velocities through soils, rocks or concrete specimens. Includes
8-channel programmable data acquisition system to record stress,
strain or other signals.
7) SWC–EPX Epoxy Kit
4-ounce epoxy kit for gluing unmounted ceramic stones to holder
8) SWC–112 Additional Specimen Rings
SWC-112-25, SWC-112-38, SWC-112-50, SWC-63, and SWC-11271. Cutting/holding specimen ring made of stainless steel. Available
ring inside diameter: 25-mm, 38-mm, 50-mm, 63-mm, and 71-mm.
Please specify diameter when ordering.
9) SWC-HCA Hanging Column Accessory
For application of low suctions between 1 and 5 kPa to soil
specimens. Contact GCTS for details.
10) SWC–MTOP Cell Top for Suction Sensor Calibration
Top for SWCC-100 Cell with 5 sealed electrical feed-through
connectors to calibrate up to 5 Fredlund suction sensors inside
standard Fredlund device.
11) PCP–PBOOST Pressure Booster
2:1 Air pressure amplifier and holding tank with a 2000 kPa (290 psi)
pressure maximum outlet pressure capacity. Includes pressure
booster, inlet and outlet pressure gages, inlet pressure adjusting
knob, and fiberglass-wrapped aluminum tank with 3.8 liter (1 gallon)
* Requires compressed air source operating at 800 to 1,000 kPa
(115 to 150 psi) pressures.
SWC Platens with Bender Elements
One (1) year parts and labor.
Standard shipping volume: 3.9 m
Standard shipping weight: 45 kg
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