Hydraulic Coupling Triaxial Test of Sandstone under Cyclic Loading Action

In deep underground engineering, surrounding rocks are subjected to cyclic loading and become prone to fractures due to the seepage pressure. To explore the mechanical properties, damage evolution, and permeability response characteristics of sandstone under cyclic loading action, three tests, namely, monotonic loading hydraulic coupling, constant amplitude and variable amplitude cyclic loading and unloading tests, were performed in this work. The mechanical characteristics, damage evolution, and permeability response characteristics of sandstone were then analyzed. Results show that, 1) under the monotonic loading hydraulic coupling action, the elasticity modulus of sandstone increases along with the confining pressure and decreases along with an increasing osmotic pressure, whereas the change in its strength is positively correlated to the elasticity modulus; 2) Given the limited compressible volume of broken sandstone, its permeability significantly decreases along with increasing confining pressure. Given that the permeable channels are changed along with the crack development laws under cyclic loading, the permeability change of sandstone after the yield stage differs from that under the conventional loading action, and the failure mode is classified as tensile-shear mixed failure; 3) A damage variable model of cyclic disturbance under cyclic loading-hydraulic coupling action was established. The conclusions obtained in the study provide references for deep underground engineering construction. © 2021 School of Science, IHU. All rights reserved.