Simulation Study on Mechanical Behavior of Bedding Yellow Sandstone Under Triaxial Cycling Loading-unloading

Bedding yellow sandstone is a common rock in tunnel construction,and the surrounding rock is under cyclic loading-unloading for a long time due to tunnel excavation and later operation.To explore the damage and fracture characteristics of bedding yellow sandstone under cyclic loading-unloading compression,the triaxial cyclic loading-unloading compression of bedding yellow sandstone with different confining pressures and dip angles was constructed with the help of PFC^2D.The stress-strain curve and fracture process were analyzed.A group of micro-parameters was obtained,which can simulate the mechanical behavior of bedding yellow sandstone under triaxial compression,and the strength and fracture characteristics obtained by numerical simulation is similar to that obtained by experiment.The stress-strain curves of specimens under cyclic loading-unloading compression can reflect the mechanical behavior of bedding yellow sandstone,and the stress-strain curve of specimens under cyclic loading-unloading compression are similar to that under monotonic loading.Fracture characteristics of sandstone samples with different dip angles are different under cyclic loading,the shear crack across the matrix when α=0°,which is similar to that under monotonic loading.Whereas when α=60°,the shear across the bedding and with the destruction in the matrix on the sides of the bedding.Under cyclic loading-unloading compression,the width of shear crack is more than that under monotonic loading.