GDS Shearbase System

Product Code : GDSSS

The GDS Shearbase System (GDSSS) is an electro-mechanical shear testing device that can be configured as either a simple shear or direct shear apparatus. The benefit of this apparatus is that the conversion between simple shear and direct shear is simple and therefore if both options are not supplied at time of build the missing option can be supplied at a later date.

To see a comparison table of selected GDS shear products, click on the link, shear products comparison.

Further Information:

Discover more shear testing equipment for soil testing.

Key features Benefits to the user
Desktop apparatus: This desktop apparatus comes with built in controllers, resulting in a small footprint of just H x 660mm, L x 660mm, D x 220mm.
Runs from mains electricity: The GDSSS comes with an integrated power supply, meaning the only laboratory service required for the system is mains electricity (110Vac – 240Vac).
No requirements for compressed air or hanging weights: The apparatus is a fully self contained, no lifting of heavy hanging weights.
Normal (axial) and shear forces are applied using GDS electro-mechanical force actuators: The use of GDS force actuators makes the system very flexible, each axis can be controlled in displacement (strain or velocity) mode as well as load control.
Topcap fixity: Topcap fixity is assured through a system of crossed roller linear guides to minimise topcap rocking during shearing.
Sample preparation and topcap support apparatus: Simple shear sample preparation and insertion into the system is made easy by using the included sample preparation and topcap support apparatus. This ensures that no load is applied to the sample during preparation and insertion.
Closed loop feedback: Axial and shear load readings are controlled under closedloop feedback.
Fully automated: For direct shear, once the shear gap has been set, the test can complete with no further user intervention. For simple shear, once the top-cap is docked all consolidation and shearing stages can proceed with no further user intervention.
Load Range (kN)

5 (Both Axis)

Sample Sizes

50, 63.5, 66, 70, 100mm (Simple Shear). 60, 100mm square (Direct Shear)

The GDS Shearbase can be upgraded to allow the system to perform both simple and direct shear tests. This is done by swapping the pedestal and top cap for a shear box. 

Simple Shear Options:
  • 10kN Axial Upgrade.
  • Bender Elements.  

Direct Shear Options:
  • 10kN Axial Upgrade.

 

Tests supported by the GDS Shearbase System, shear testing 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.

Constant Normal Stiffness

A constant normal stiffness condition may be specified and maintained when testing specimens within GDS direct shear and direct simple shear apparatuses. This condition allows for both the normal stress and normal strain to vary as a specimen is sheared based on the contractive and dilative tendencies of the geo-material – here dilation results in increased normal stress and specimen height, while contraction results in decreased normal stress and specimen height. The magnitude of normal stress and normal strain variation is proportional to the constant normal stiffness value specified by the user, entered in units of kN/mm or kPa/mm. Practical applications of such a test condition include modelling the interface between piles socketed or grouted into a geo-material.

Cyclic Simple Shear

The Dynamic Cyclic Simple Shear Module allows you to run two tests. 

Test 1: Dynamic control of Axial actuator for either axial displacement (mm) or axial force (kN).
Test 2: Dynamic control of horizontal (shear) actuator for either shear displacement (mm) or shear force (kN).

Cyclic Testing, Slow

Slow cyclic testing may be performed on all GDS triaxial testing apparatus with the appropriate software modules.  The speed the cycles can be applied is determined by the performance of the system.  A standard load frame generally only used for quasi-static testing can perform cyclic testing with periods of around 5 minutes when coupled with GDSLAB control and data acquisition software. Please note: Some apparatus may require additional components or software modules to perform certain tests.

Cyclic loading of samples under either load or strain

Cyclic loading refers to the repeated loading of a sample.  All GDS systems can imply this loading either under load control, or under strain (displacement) control.  Load control will be via feedback from the load cell and displacement control will be via the feedback from the displacement transducer.  Load and displacement control can be performed by all GDS system.  The speed of the cyclic loading depends on the frequency performance (i.e. the dynamic performance) of the system in question.  Dynamic stress control is possible, but only available on the most advanced GDS dynamic because of the additional processing required to calculate the sample area during the cycles.  Please note: Some apparatus may require additional components or software modules to perform certain tests.

Direct Shear Tests

Direct shear tests: The sample is contained inside a rigid box with a horizontal split line at the mid-height of the sample. The shear force is applied to the sample by moving the two halves of the box horizontally relative to each other. The intension is to induce a shear plane to form between the two halves of the sample. Properties can be obtained for the material prior to shear and post failure or residual. 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.

Maximum Shear modulus

Determination of the maximum (i.e., very small strain) shear modulus of a specimen. 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.

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.

Simple Shear

Simple shear tests: Simple shear samples are restrained by either thin horizontal bands or by wire reinforced membranes. The topcap and pedestal are moved horizontally, relative to each other to apply the shear loading. The sample is allowed to deform in a lozenge shape rather than just forming a horizontal shear plane as for direct shear testing. The simple shear test can be used for carrying out tests that rotate the principal stress direction as well as tests that determine the shear strength / stiffness of the material. 

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 Shearbase System, shear testing equipment for soil testing :-