The GCTS Direct Shear Testing System for Soils and Asphalts (SDS-300) features electro-hydraulic closed-loop digital servo control of the shear and normal loads for test automation. Loads or deformations for both the shear and normal actuators can be prescribed for automatic performance of conventional direct shear tests as well as more advanced tests. This system can be easily programmed to perform tests such as the constant normal stiffness test where the normal load is a function of a prescribed stiffness for simulating actual compressibility of a ground shear plane (e.g. soil-pile interaction).
The SDS-300 is especially well-suited to test coarse granular materials and simulate interface materials because of its high load capacity, ability to accommodate large specimens, and elimination of vibrations that can disturb or compact granular specimens.
Included with this system are loading plates with a square grid of retractable pins that help to grab different types of samples, such as soils, asphalt and other materials. Also included is a water reservoir to submerge specimens during testing.
The top shear box can be horizontally translated and the bottom shear box is mounted on sliding bearings to minimize friction. Set screws with nylon tips are used to adjust the shear gap. The top shear box is suspended on springs to balance its weight, causing normal load readings to be extremely accurate. The shear boxes also ensure that shear transfer is done through the top of the shear boxes rather than the sides, making this system the most accurate large scale direct shear testing system on the market.