Numerical Study on the Shear Damage Behavior of Sandstone under Normal Disturbance Effects

The study focused on examining the impact of initial normal stress and normal disturbance amplitude on the degradation of rock mass in a complex stress environment. Using PFC2D numerical simulation software, various experimental characteristics of rock samples were analyzed, such as strength properties, damage patterns, and stress evolution. The results revealed that: Under constant normal stress conditions, the shear strength increases with an increase in the normal stress. From microscopic analyses, the normal stress effectively compacts the particles within the rock, which prompts more particles to contribute to the shear strength of the rock. Consequently, the mechanical property of the rock was improved, and the number of cracks during the damage process also increases. The disturbance causes internal damage and destruction to the rock samples thus degrading strength, which becomes more evident as the amplitude increases. Before the peak strength, the damage effect is dominant, while after the peak strength, the contact effect combined with the damage effect contributes to the formation of the shear plane cracks and wing cracks. Besides, the stress concentration along the shear direction becomes more pronounced as the normal stress increases. These findings have valuable implications for the study of rock stability under disturbance.