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:

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.

3 x electromechanical, high accuracy, encoder controlled actuators.

Axial Force Accuracy

Typically <0.1%


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

Displacement Range

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

Displacement Resolution


Load Range (kN)

5 Axial Axis, 2 Shear Axis.

Operating Frequency (Hz)

0 (Static) to 1Hz


240V or 110V 50/60Hz 1 ph

Sample Sizes

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

Weight Approx (kg)


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