Mechanical Properties and Energy-Dissipation Mechanism of Frozen Coarse-Grained and Medium-Grained Sandstones

Mechanical behavior and deformation essence of frozen soft rock under complex environmental conditions is crucial for frozen shaft engineering. The strength and deformation properties of sandstones under different low temperatures were investigated by conducting uniaxial and triaxial compression tests. The energy characteristics of rocks during the deformation were analyzed. The micro-structure features were obtained by scanning electron microscopy (SEM) test. The results show that the sandstones have a noticeable pore compression stage and the medium-grained sandstone is more pronounced. The rock strength decreases and increases non-linearly with the increase of temperature and confining stress, respectively, and the factors affect each other. The elastic modulus increases with the decrease of low temperature, while the changes in Poisson ratio is opposite. In addition, the total strain energy, elastic energy and dissipated energy of sandstones have different evolution laws, revealing the deformation and damage mechanism of rocks. Last, the internal reason of differences in the mechanical properties of sandstones is explained from the microstructural perspective. The above research conclusions could provide a certain theoretical basis for the stability control of shaft engineering in northwest China.