Cyclic mobility following plastic strain accumulation in sand

Hybrid failure modes/mechanisms under non-symmetrical cyclic loading (partial stress reversal) have received little attention. This paper presents data from cyclic undrained triaxial tests of sand, with initial static shear stress, to investigate a hybrid failure mechanism that controls the behaviour of dilative sand in a narrow range of non-symmetric stress reversal levels. The results indicate that cyclic mobility (Mob) can emerge following significant accumulation of plastic strain. Transition from plastic strain accumulation to Mob can be associated with the instability and phase transformation lines in extension. Two different types of transition and the mechanisms involved are discussed.