On the influence of the polarization and the shape of the strain loop on strain accumulation in sand under high-cyclic loading

This paper presents results of cyclic triaxial (CT) tests on sand with a simultaneous variation of the axial and the lateral stresses. Furthermore, a cyclic multidimensional simple shear (CMDSS) device and corresponding test results are discussed. For in-phase cycles with a constant strain amplitude it is demonstrated that the accumulation rate is independent of the polarization of the cycles in the strain space. Polarization changes lead to a temporary increase of the accumulation rate: they increase the effectiveness of compaction. For out-of-phase (e.g. elliptical) cycles the shape of the strain loop significantly influences the residual strain. A circular strain loop generates twice larger accumulation rates than a one-dimensional strain loop with identical span. The accumulation rate is not influenced by the circulation of the strain loop. It is shown that the direction of accumulation (so-called “cyclic flow rule”) is only moderately affected by the polarization and the shape of the cycles.