Characterization of the deformation behavior of fine-grained sandstone by triaxial cyclic loading

In order to study the deformation behavior of fine-grained sandstone subjected to cyclic loading, a series of triaxial cyclic compression tests were performed under different confining pressures in the laboratory. Each of the tests combined constant-amplitude cyclic loading and increasing-amplitude cyclic loading. The experimental results showed that the evolutions of the elastic modulus and Poisson's ratio with cycles had 3 variation modes according to the applied deviatoric stress. Within a given stress level, the axial and lateral irreversible strain initially increased with a decreasing rate, followed by steady-state increases before failure. When the specimens approached failure, an accelerated increase in the irreversible strain occurred. Under lower stress levels, the volumetric strain was characterized by compaction-dominated behavior. However, it changed from compaction to dilation within each loading cycle under higher stress levels. SEM (scanning electron microscope) tests were conducted on unruptured specimens to study the deformation mechanism of the fine-grained sandstone during cyclic loading. This marks the beginning of a study that aims to provide a reference to the design, construction, and operation of hydropower stations in China.