Direct and Residual Shear Testing Machines

Direct Shear Testing Machines

The direct shear test is a method of determining the consolidated drained shear strength of soils. The direct shear test is performed by placing a vertical load on the sample which is in a horizontally split box. After the vertical load has consolidated the sample, the two halves of the box are "pulled" apart relative to each other, which causes a shear load to be measured on a load measuring device. Once the soil has been sheared to its shear strength, there is failure and the load rapidly drops off. This procedure is repeated (usually three times) under different vertical loads. A "failure envelope" can then be drawn on a graph which allows engineers to design slopes, dams, foundations, etc.

The direct shear test is used to assess what soil strength might be in a field situation where complete consolidation has occurred under the existing normal stresses. Failure is reached slowly under drained conditions so that excess pore pressures are dissipated. The results from several tests may be used to express the relationship between consolidation stress and drained shear strength. Direct shear testing is often used when trying to determine the shear strength of sandy materials.

Direct shear devices can also be used to measure residual shear strength. Residual strength is the shear strength of the material that is exhibited after a failure (exceeding of initial shear strength) has occurred. Residual shear strength testing is very important in earthquake prone areas.

Humboldt offers a wide variety of choices in Direct Shear Machines. From automated and semi-automated pneumatic machines to a choice of three dead-weight models, we have a machine that will fit your application perfectly.

The HM-5760 is an automatic machine featuring a stepper-motor drive system and a 7" touch-screen display that allows the operator to control and monitor all test functions. This unit comes with the Next direct shear software module.The HM-5760 is built around Humboldt‘s integral, 4-channel data logger with touch-screen control, which allows this model to be used as a standalone device capable of full test control and data logging. It can also be controlled by a networked computer at any location with access to the network.

Our HM-5755 is a semi-automatic machine identical to the HM-5760 except that pneumatic loads are controlled by a manual valve located on the front panel for easy use.

For dead-weight load machines, we offer three different setups. The HM-5750A and HM-5750D models are essentially semi-automatic machines, which utilize manual loading weights for load control. Both machines are built around Humboldt‘s integral, 4-channel data logger with touch-screen control, which allows them to be used as a standalone device capable of test control and data logging. They can also be controlled by a networked computer at any location with access to the network. The HM-5750A utilizes an analog load cell and strain transducers, while the HM-5750D uses a digital load ring and digital indicators.

Finally, the HM-5750 provides an economical alternative by using mechanical dial gauges in your load ring and to measure the Horizontal and Vertical displacement.