Apparent Creep of Saturated Sand Caused by Intrinsic Cyclic Loading

An interesting phenomenon, designated as an apparent creep of saturated sand, is described on the basis of experimental data obtained from triaxial quasi-drained-controlled tests. In such tests, external stresses were kept constant while the pore pressure was cyclically changed (intrinsic cyclic loading). It is a kind of cyclic loading that takes place in seabeds, where the pore pressure changes cyclically because of the action of water waves. During the experiment, both vertical and horizontal strains were recorded. It is shown that these strains gradually increase as functions of the number of loading cycles in such a way that the volume of the specimen is constant, and only the deviatoric strain increases. The experimental curve resembles the creep curve for solid materials, in which real time is replaced by the number of loading cycles. The experiments are described and discussed, and a simple model of the phenomenon observed is proposed.