An experimental study of cyclic loading of sandstone under different water contents

In order to explore the difference in the mechanical behavior of sandstone under cyclic loading with different water contents, the uniaxial cyclic loading and unloading tests are conducted for the sandstone under dry, natural and saturated conditions. The results show that the strength of the saturated, natural and dry conditions decreases but the deformation increases because of the softening effect of physical chemistry. The unloading modulus increases first and then decreases with the increasing cycle times and the higher the water content, the smaller the unloading modulus in the same cycle. The volume strain occur an inflection point when the cycles are coincided with the turning point of unloading modulus through the bad times. The energy value with cycles is a power function of the growth and in the same cycle, the higher the water content is, the greater the energy value of the sandstone is. The damage definition based on energy dissipation shows that the initial damage value of sandstone is not zero, and the damage evolution process reduces and then increases. The damage amount of the saturated, natural and dry sandstone increases in turn in the same cycle.