Soil-Water Characteristic Curve

GCTS offers two solutions for determining the soil-water characteristic curve (SWCC) for a given soil: the SWC-050 and the SWC-150.

The GCTS SWC-050 provides an economical and reliable way to determine the soil-water characteristic curve on up to three samples simultaneously. This system includes three cells that connect to a single pressure application system to apply suctions up to 500 kPa. Each cell allows water to escape from below the samples as suction is increased, so the gravimetric water content can be measured by weighing the entire cell, rather than removing the sample for each measurement. Each cell can be fit with an optional deformation sensor to measure the axial deformation of the sample during the measurements. These deformation sensors and the pressure transducer in the pressure application system are connected to a GCTS DataCube Wireless Data Acquisition Box for automatic measurements. The user can connect a wireless device (Android or Apple) to the DataCube via Bluetooth to record the deformation and pressure measurements. All data is stored in the DAQ-2W, so the user will only need to connect to the box to start the test and to collect all data at the end of the test. The SWCC of the samples is automatically plotted in the phone application, and the data can be easily sent to an email in a spreadsheet format.

The Fredlund SWCC Device (SWC-150) is a flexible unsaturated soil testing apparatus to measure the soil water characteristic curve while applying various stress states. The SWC-150 can be used to obtain the complete soil-water characteristic curve (SWCC) for a soil sample. The Fredlund SWCC device allows the operator to control matric suctions from near zero values up to 1,500 kPa (215 psi), and is capable of applying one-dimensional loading, Ko, to a specimen with a diameter up to 75 mm.  The cell is constructed from stainless steel and includes the necessary plumbing and valves for periodic flushing and measuring of diffused air. Several different high air-entry-value (HAEV) ceramic stones can be easily interchanged. Dead weights can be used to apply normal stresses. An optional pneumatic load frame loader is available to apply larger stresses. Through its convenient design, the apparatus allows the use of a single soil specimen to obtain the entire SWCC with any number of data points.



  • Perform three tests simultaneously with one shared pressure control system
  • Applied suctions up to 500 kPa
  • Measure vertical deformation during test
  • Built of lightweight material to obtain gravimetric water content without removing the sample from the cell
  • Auto-seal quick disconnect to easily remove pressure line while weighing device
  • See-through acrylic cell wall
  • Internal spring to maintain porous disc contact with specimen
  • Includes 5-bar HAEV stone



  • Simulates vertical in-situ pressure state
  • Tracks volume changes
  • Tracks water content
  • Applied suctions up to 1,500 kPa
  • 75 mm maximum specimen diameter
  • Both drying (de-adsorption) and wetting (adsorption) curves
  • Dual pressure gauges and regulators for precise pressure control
  • Stainless steel construction with hand-operated knobs for fast setup
  • Pressure compensator on the loading ram
  • Flushing ability and measurement of diffused air
  • Optional hanging column for applying suctions below 5 kPa
  • Optional heater for preventing vapor condensation inside the cell
  • Optional null-type initial suction measurements on undisturbed specimens available

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Soil-Water Characteristic Curve

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