Shear devices
Shear strength means the capability of soil or rock material to compensate strain and tension stresses without failure or plastic flow. When the internal friction resistance is exceeded, failure occurs. There is a low residual friction in the following sliding stage.
The shear strength of a soil is mainly controlled by its chemical and mineralogical composition, internal structure, water and pore content as well as by its mechanical load.
The shear strength of a soil is an important criteria for soil mechanic investigation in civil engineering, building and foundation. There are different methods to determine the shear strength of soil or rock sample. You can either use a shear testing apparatus, a shear vane tester, an uni- or triaxial compression device.
In an usual shear apparatus the axial load on the soil sample is produced mechanically by weights or automatically with an electro-mechanical, or hydro-pneumatical testing machine.
Conducting a Direct Shear test, the shear plane is gained by the gap between the split sample frame. In contrast performing a Simple Shear test, the sample is framed by numerous metal rings to afford a less constricted development of the shear gap. In the testing procedures described above, the soil sample is pushed together horizontally and the shear resistance correlates directly with the shear stress. In a Ring Shear device both sample halves are turned against each other and the shear strength results comparable with the shear vane test in the measured torque. The force, strain and travel which occur during the test procedure can simply be measured by mechanical gauges or they are recorded by digital transducers with control- and evaluation-software.
Along the decades of developing and manufacturing any kind of shear devices, the assortment of Wille Geotechnik® not only includes manual and automatic standard testing machines. We are known to provide complex special solutions, like Large Shear apparatus and dynamic plants. In support of the geotechnical testing machines, Wille Geotechnik® provides a competent service for accessories, spare parts and repair.
Beside the pocket and field vane tester Wille Geotechnik® has designed a solid and practical laboratory vane testing device. In regard to DIN 18137 the undrained shear strength of a soft cohesive soil is distinguished as the torque by vane testing.