GDS Constant Rate of Strain Cell (CRS in Load Frame type)

Product Code : GDSCRS

The GDS Consolidation Constant Rate of Strain cell (CRS) is designed primarily for advanced commercial testing laboratories who want to reduce the time required to complete a consolidation test. The CRS cell fits either a new GDS or existing load frame in place of a Triaxial cell.

 The load frame based one dimensional consolidation cell is capable of applying back pressure and measuring pore pressures from 1 or 3MPa (low pressure versions) to 20MPa (high pressure version). Also available with temperature control.

Further Information:

Discover more consolidation system equipment for soil testing.

Key features Benefits to the user
Stress increments applied gradually: The advantage of this method is that the time required to complete a consolidation test can be reduced significantly.
Controlled back pressure (water) is applied to the sample and drainage is allowed through the base of the apparatus: Allows excess pore pressure to be monitored so tests can run at maximum speed and hence increase specimen throughput. 
Run the entire test from start to finish: More efficient testing as no waiting for user inputs.
Interchangeable range submersible loadcell: Enables the user to run tests on soils of different stiffness and match the load transducers accordingly, giving greater accuracy of results and seal friction does not effect load readings.
Construction material:
1MPa: Anodised aluminium with perspex outer cell wall.
3MPa: Aluminium.
20MPa: Stainless steel.
Integral cutter / sample ring: Disturbance on samples is reduced by having a cutting edge integrated into the sample confinement ring. 
Temperature Control:GDS’ Constant Rate of Strain cell is available with temperature control.
Load Range (kN)

10, 50 (Requires LF50 Frame)

Pressure Range (MPa)

1, 3, 20

Sample Sizes

50, 63.5, 70, 75, 100mm x 22mm

  • Unsaturated Testing.
  • Temperature Control.
  • Permeability Testing.
  • Open-topped CRS.
More information on consolidation test equipment.

 

Tests supported by the GDS Constant Rate of Strain Cell (CRS in Load Frame type), consolidation system equipment for soil testing :-

Axial Compression

An axial compression test determines the behaviour of geo-materials when the major load is applied in the axial direction. The specimen load and displacement is recorded while the specimen is compressed. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Consolidation Testing

Triaxial consolidation refers to the application of a constant cell and back pressure to the sample whilst monitoring the volume change within the sample.


One dimensional consolidation refers to the application of a load to the top of a sample contained within a fixed ring.

Constant Head Permeability

The constant head test simply maintains a constant differential in pressure between the top and the base of the specimen (top pressure is always set higher than the base pressure). The flow is then measured on the top controller and the base controller.  Please note: Some apparatus may require additional components or software modules to perform certain tests.

Constant rate of Loading (CRL) Consolidation

Provides a controlled ramp of load while the back pressure is maintained. There is also the option to limit the rate of strain if a specified hydraulic gradient across the sample is exceeded.

Constant rate of strain (CRS) Consolidation

Provides a controlled ramp of strain while the back pressure is maintained. There is also the option to limit the rate of strain if a specified hydraulic gradient across the sample is exceeded.

Continuous Infinite Volume Flow (either target or ramp)

Some geotechnical applications require the continuous flow of fluid, either under pressure control or via a rate of fluid flow.  GDS manufacture an Infinite Volume Controller (IVC). By connecting 2 GDS pressure/volume controllers in parallel, the IVC system automatically switches between them when they run out of volume thus providing a seamless supply of pressure with unlimited volume capacity.  The IVC can be used with any 2 pressure controllers from the GDS range, i.e. advanced, standard or enterprise. Please note: Some apparatus may require additional components or software modules to perform certain tests.

K0 (K-Zero)

Kzero conditions (or specifically the coefficient of earth pressure at rest) in the context of laboratory testing are where a sample is required to be loaded whilst keeping the area of the sample a constant.  Kzero conditions are maintained in a n oedometer by design due to the radial constraint, however in an oedometer the radial stress cannot be measured therefore the K-zero condition is not measureable.  A Kzero test in a triaxial cell allows Kzero conditions to be applied and measured. The Kzero module allows you to run two tests. 

  • Test 1: Kzero using ramp RADIAL STRESS with direct radial transducer measurement: Uses a direct reading of the specimen diameter to enable the test control to maintain zero diameter change.
  • Test 2: Kzero using ramp RADIAL STRESS with back volume change measurement: Uses the change in volume of the specimen to calculate a theoretical new specimen height thus ensuring the diameter change remains zero.

Please note: Some apparatus may require additional components or software modules to perform certain tests.

Load Control (Static)

Enables application of load to a specimen for tens of seconds or more, and at frequencies less than 0.1 Hz during cyclic loading. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Multi-stage Testing

The procedure for conventional triaxial tests requires three separate soil specimens to be sheared to failure under different confining pressures so that Mohr-Coulomb failure envelope can be determined and soil shear strength parameters can be obtained. An alternative procedure is the multi-stage triaxial compression test, which requires only one soil specimen to be tested at three stages of shearing with different confining pressures.


There main advantages of multi stage soil testing is the requirement for fewer soil specimens, as well as reduced testing time.  The advantage of performing the test with 3 separate samples is that if one of the samples is unsatisfactory (perhaps due to sample disturbance for example) then it is likely to be noticed when the Mohr circles are plotted, whereas this could remain unnoticed in the multi stage test. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Oedometer / Consolidation

Uses a datalogger to take settlement readings from a hanging weight oedometer system.  Alternatively, GDS produces an automated oedometer which completely automates one dimensional consolidation testing.

Pore Water Volume Change

Soil testing involves the application of pressure (stress) and the resulting measurement of strain either by measuring displacements or volume change. GDS pressure/volume controllers can apply pressure and measure volume change, or alternatively can apply volume change and measure the resulting pressure. Essential for soil testing.  Please note: Some apparatus may require additional components or software modules to perform certain tests.

Quasi-Static (low speed/creep) Tests

Quasi-static refers to slow speed tests.  Creep tests require accurate displacements to be measurable whilst a continuous, sometimes long term loading is accurately applied. Please note: Some apparatus may require additional components or software modules to perform certain tests.

RAMP and CYCLE pressure or volume change (Saturation Ramp)

Saturation ramp allows you to independently increase or decrease the Cell Pressure and the Back Pressure. The saturation ramp is used to steadily change the pressures in the system either keeping a constant effective stress or change to a desired effective stress.

Static Displacement

A static displacement test involves applying and maintaining a constant displacement to the specimen. The load response can subsequently be observed. Alternatively this may refer to cases where a displacement, which may vary, is applied to a specimen for tens of seconds or more. Please note: Some apparatus may require additional components or software modules to perform certain tests

Static Load

A static load test involves applying and maintaining a constant load on the specimen. The displacement response can subsequently be observed. Alternatively this may refer to cases where a load, which may vary, is applied to a specimen for tens of seconds or more. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Stepped Loading

Stepped Loading provides a means to increase the specimen axial load, whilst maintaining a constant back pressure and measuring the back (pore) volume change. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Standards for the GDS Constant Rate of Strain Cell (CRS in Load Frame type), consolidation system equipment for soil testing :-