STRESS-PATH DEPENDENT SHEAR-STRENGTH OF SAND

Failure envelopes of sands arc often considered to be nonlinear depending both on relative density and stress level. Triaxial tests that were performed on clean alluvial-quartzitic Zbraslav sand were used for analyzing the form of the failure envelope. In addition to relative density and stress level, the stress path (tests with constant-cell pressure were compared with tests with constant-mean stress level) has been found to affect the shear resistance as well. Only tests with constant-mean stress produce nonlinear-failure envelopes. Up to the peak-stress difference, no shear bands were observed. Rough platens were used to simplify the procedure since the specimen's restraint was found not to affect the shear resistance for diameter to height ratio 1:2. The writer uses the percolation theory to provide the physical interpretation of the experimental results.