Influence of irregular loading and frequency on the cumulative damage and dissipated energy of dry loose sand under cyclic simple shear

This paper presents an experimental study involving cyclic simple shear (CSS) tests performed on dry loose Ottawa sand at an initial normal stress of 200 kPa and sheared under a constant volume condition. Horizontal shear loading involved 3 frequencies, andboth uniform sinusoidal and irregular loading.The CSS tests involving uniform sinusoidal loading showed that for the 3 frequencies considered, the cycles to failure plots did not vary significantly with frequency. The study of the influence of irregular loading on the developed cumulative damage and dissipated energywas carried out by comparingthesequantities with measured values in CSStests on similar samples tested under uniform loading. The results show that thepredictions of equivalent uniform cycles, done using the P-M cumulative damage hypothesis,are quite variable and that the accumulation of damage from irregular loading in most cases was observed to develop faster than predicted using equivalent uniform cycles. In contrast, the dissipated energy per unit volume until failure measured inall CSS tests (uniform and irregular loading, and 3 frequencies), was found to be relatively constant, and supports the use of energy-based approaches to study cyclic behavior of loose dry sands.