GDS Electro-Mechanical Dynamic Cyclic Simple Shear

Product Code : EMDCSS

The GDS Electromechanical Dynamic Cyclic Simple Shear Device (EMDCSS) is for simple shear testing, which can be upgraded to direct shear. It is capable of carrying out dynamic cyclic tests from small strain (0.005% shear strain amplitude) to large strain (10% shear strain amplitude), as well as extremely accurate quasi-static testing. This is the choice for a no-compromise simple shear machine with the greatest range of testing capability. The perfect choice for advanced commercial testing or academic research.

Discover more shear testing equipment for soil testing.

Key features Benefits to the user
Teflon coated low friction retaining rings: A cylindrical soil specimen is laterally confined by teflon coated low friction retaining rings, ensuring a constant cross sectional area (or K-zero conditions).
Electro-mechanical actuators that give superior performance, reduce space and provide cost savings: Electro-mechanical actuators can carry out tests up to +/-1mm at 5Hz, with greater accuracies than comparable pneumatic actuators. Mains powered means no external noisy power pack is required and as opposed to pneumatic systems electro-mechanical systems draw only the power that is required.
Active height control: Therefore constant volume conditions are enforced i.e Simple Shear. No manual intervention between stages plus little or no effects of vertical compliance.
Axial & Shear linear guidance provided by super-stiff crossed-roller bearings: 200mm bearing length not only provides stability while ensuring minimal rotation of the topcap during shearing, allowing testing to be simple shear rather than rotational motion, but also provides high load capacity with low friction with accurate linear guidance.
GDS shear loadcell: Designed so that shear force is measured in front of the linear guides, as such the shear force measurement does not include frictional errors.
Dimensions

1200mm (H) x 500mm (L) X 770mm

Displacement Range

axial = +/- 25mm, shear = +/- 15mm: Accuracy = <0.1% FSO (In practice, axial range is +/-50mm to aid sample placement, however measured stroke is +/- 25mm, and shear stroke is supplied as standard with a high accuracy +/-10mm LVDT).

Displacement Resolution

24bit (i.e. +/- 20mm = <0.6μm, +/- 15mm = +/- <0.5μm, +/- 2.5mm = <0.1μm)

Load Range (kN)

5, 10

Operating Frequency (Hz)

0 to 5Hz

Power

240V or 110V 50/60Hz 1 ph

Sample Sizes

Direct: 60mm sq., 63.5mm round. Simple: 50, 63.5, 66, 70, 100 and 150mm

Weight Approx (kg)

220

  • P and S wave measurements with Bender Element system.
  • Direct shear

Alternative Direct Simple Shear Test Products or just Direct Shear Test Equipment

 

Tests supported by the GDS Electro-Mechanical Dynamic Cyclic Simple Shear, 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.

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 (Dynamic)

Enables application of load to a specimen for approximately less than ten seconds, and at frequencies greater than 0.1 Hz during cyclic loading.

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.

User defined waveforms

Dynamic cyclic triaxial testing is usually performed with a cyclic loading pattern which is the shape of a sine wave.  Some experiments require a unique waveshape to be applied to the soil, for example in recreating earthquake loading from a measured seismograph trace.


All GDS advanced dynamic systems allow user defined waveforms to be used, with the enterprise level dynamic systems having user defined waveforms as an optional feature.

Standards for the GDS Electro-Mechanical Dynamic Cyclic Simple Shear, shear testing equipment for soil testing :-