![]() Assemble the shear box (put porous stone and the gripper disk together).Stabilize the bottom part of the shear box by fixing the 2 screws.Place the shear box inside the shearing device.Measure the height and diameter of the shear box.Therefore, the results of the test are not representative of the actual soil’s behavior. Otherwise, if pore water pressure increases during the test, the shear strength of the sample will be underestimated.Ĭommon errors that occur during direct shear testing include disturbing the sample before the test, not allowing it to fully consolidate or selecting a shearing rate that is too high.ĭisturbance usually affects the sample’s structure and reduces its strength. ![]() Therefore, it is crucial that the sample is saturated and the consolidation process is completed before the shearing begins. The shearing device is not equipped with sensors to measure pore pressure during the test. The vertical and horizontal deformation are calculated via dial gauges. Ιt is controlled by a servomotor device and a gear box assembly. This rate depends on the soil characteristics and should be relatively small to prevent pore pressure built up thus providing sufficient drainage. The shearing device applies a constant displacement rate with 5% accuracy tolerance. At this stage, the metallic plates are screwed together.īefore the shearing stage begins, one metallic plate is slightly raised to ensure the separation of the two halves of the apparatus and secure that the normal and shear loads are transmitted only through the specimen.Īfterwards, a shearing stress is applied along the pre-determined horizontal plane until the specimen fails. This phase is known as the consolidation stage and proceeds in an incremental manner similarly to that of a typical consolidation test. Initially, a direct normal pressure is applied at the top of the sample using a leverage weight or via a pneumatic system. The shear box is then placed in the shearing device.
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