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Variable Direction Dynamic Cyclic Simple Shear

Product Code : VDDCSS

 The VDCSS (Also known as Bi-directional) allows direct simple shear to be performed in two directions, rather than the standard single direction. This is achieved by having a secondary shear actuator that acts at 90 degrees to the primary actuator.

When used as a variable direction machine, the secondary shear axis can be used independently or in conjunction with the other shear axis. Therefore, simple shear may be performed in any horizontal direction. Used for simulating change in wind direction on a wind turbine without having to remove the sample. 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.

Variable Direction Dynamic Cyclic Simple Shear
specification datasheet (PDF)
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Key features Benefits to the user
Active height control:
Constant volume conditions are enforced i.e simple shear. No manual intervention is required between stages.  Little or no effects of vertical compliance due to the extremely stiff system design, critical for high quality DSS testing.  
GDS Shear Loadcell:
Designed so that shear force is measured in front of the linear guides for both X and Y axes such the shear force measurement does not include frictional errors.
Low friction retaining rings:  A cylindrical soil specimen is laterally confined by coated low friction retaining rings ensuring a constant cross sectional area (K-zero condition). The ring substrate is Aluminium Bronze which is a hard, bearing grade material, providing less strain, less potential to deform and scratch than aluminium. The nickel based coating has high concentrations of sub-micron sized PTFE particles to provide excellent low friction and break out force performance even after years of use.
Electro-mechanical actuators that give superior performance, reduce space and provide cost savings: Electro-mechanical actuators can carry out tests up to 1mm at 1Hz, with greater accuracies than comparable pneumatic actuators. Mains powered means no external noisy power pack is required and as opposed to pneumatic/hydraulic systems, electromechanical systems draw only the power that is required.
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 (an important aspect for testing to international standards), but also provides high load capacity with low friction with accurate linear guidance.
Actuators

3 x electromechanical, high accuracy, encoder controlled actuators.
Axial Force Accuracy

Typically <0.1%
Dimensions

1200mm (H) x 800mm (L) X 610mm (W)
Displacement Range

Shear axis +/- 10mm (+/-30% shear strain), Normal axis +/- 25mm (+80% consolidation strain).
Displacement Resolution

0.3um
Load Range (kN)

5 Axial Axis, 2 Shear Axis.
Operating Frequency (Hz)

0 (Static) to 1Hz
Power

240V or 110V 50/60Hz 1 ph
Sample Sizes

50/70mm (D), 20 to 30mm height
Weight Approx (kg)

180

Confined Pressure Testing: 

An alternative system, the MDDCSS, may be purchased to enable application of confining and back pressures to test specimens. This allows specimens to be back-pressure saturated, with excess pore pressures directly recorded during simple shear tests, see datasheet for more information.

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

 

Tests supported by the Variable Direction 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.

Axial Compression soil test equipment
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.

Constant Normal Stiffness soil test equipment
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 Simple Shear soil test equipment
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 Testing, Slow soil test equipment
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.

Cyclic loading of samples under either load or strain soil test equipment
Dynamic Cyclic Axial Stress Capability

Dynamic cyclic axial stress is an extremely advanced test, only available on dual axis advanced dynamic triaxial testing systems.  During the cyclic loading the area of the sample is continuously calculated allowing the sample stress to be accuratelly maintained at the desired amplitude and wave-shape.

Dynamic Cyclic Axial Stress Capability soil test equipment
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.

K0 (K-Zero) soil test equipment
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 (Dynamic) soil test equipment
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.

Load Control (Static) soil test equipment
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.

Maximum Shear modulus soil test equipment
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.

Multi-stage Testing soil test equipment
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.

Oedometer / Consolidation soil test equipment
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.

Quasi-Static (low speed/creep) Tests soil test equipment
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. 

Simple Shear soil test equipment
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 Displacement soil test equipment
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.

Static Load soil test equipment
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.

Stepped Loading soil test equipment
Variable Direct Simple Shear

Enables load or displacement to be applied to a simple shear specimen in two horizontal shear directions. 

Variable Direct Simple Shear soil test equipment

Standards for the Variable Direction Dynamic Cyclic Simple Shear, shear testing equipment for soil testing :-