Experimental Study and Analysis of Creep and Stress Relaxation in Granular Materials

Experiments have been performed to study the time-dependent behavior of Antelope Valley sand in triaxial compression. Observations of time effects in tests with constant strain rate, creep tests at different stress levels and stress relaxation tests initiated at different amounts of axial strain are presented. Some of the drained creep behavior was reported previously (Lade and Liu 1998) and based on analysis of this behavior, a model for creep in sand has been presented (Lade and Liu 2001). Additional experiments on strain rate effects and stress relaxation of the same sand are reported here and compared with results for creep behavior in sand. It is found that the classic time effects found in most materials, i.e. increasing stiffness and strength with increasing strain rate and corresponding creep and stress relaxation behavior, are not observed in sand.