A Low-Compliance Bi-Directional Cyclic Simple Shear Apparatus
A new simple shear apparatus is described which can apply bi-directional simple shear cyclic and monotonic loading. Cylindrical specimens are placed in a pressure chamber so that confining pressure and back pressure can be applied. Bi-directional shear loads are applied to the specimen´s base, which is mounted on a series of two horizontal rolling tables which can be independently loaded in two orthogonal directions while preventing cap and base platen “rocking.” A computer-automated feedback-loop-controlled pneumatic servovalve system provides excellent control of loads and displacements. Displacement control during cyclic tests on softening specimens is improved by the inclusion of a parallel stiffness. Procedures and test results are presented for three different undrained cyclic simple shear loading conditions and for a strain-controlled monotonic loading condition.