Deformation and Dissipated Energy of Sandstone Under Uniaxial Cyclic Loading

The fatigue deformation of sandstone was investigated in the laboratory using uniaxial cyclic loading tests. These tests showed that: (1) Fatigue deformation can be divided into three phases, the primary, steady, and acceleration phases. The initiation of the acceleration phase indicates that the sample is about to fail. (2) Sandstone samples subjected to conventional compression tests fail in a different way than samples subjected to cyclic loading tests. The former mainly fail along shear and tensile fractures whereas the latter are transformed into a pile of many large and small fragments. (3) When sandstone is undergoing cyclic loading, the extent of deformation and the dissipated energy change synchronously, so the energy dissipation curve can reflect the fatigue deformation of the sandstone. (4) A model for sandstones deformed by cyclic loading is put forward that describes the U-shaped distribution of energy dissipation points on an energy dissipation-cycle number plot well.