Study on the evolution law of fracture of sandstone under cyclic water intrusion based on particle-cement coupling damage

Abstract

To investigate the process of rock fracture under load and the accumulation of micro-damage in rocks under cyclic water intrusion, a particle-cement coupling damage model based on discrete element method was proposed. This model establishes a functional relationship between mineral dissolution caused by cyclic water intrusion and the number of particles N and cementation radius \(R\) in PFC^3D parameters, aiming to simulate sandstone after cyclic water intrusion. Furthermore, it analyzes the contact force chain, microcracks, cementation evolution, and failure patterns during the loading process of rocks under cyclic water intrusion. The research results show that: (1) Under cyclic water intrusion, the mineral particles and cemented minerals in sandstone continue to dissolve. After 20 cycles of cyclic water intrusion, the loss of particle skeleton is 4.3%, and the loss of cemented minerals is 63.6%, which leads to a significant deterioration of the mechanical properties of rock. (2) The force chain characteristics and distribution at the peak stress and yield failure stages are greatly influenced by the degradation effect of cyclic water intrusion. (3) The number of cyclic water intrusions is positively correlated with the cementation failure rate and the number of microcracks, but negatively correlated with the crack initiation stress. Cyclic water intrusion changes the distribution of micro-shear cracks, reduces the integrity of the specimen during fragmentation, and the distribution of micro-shear cracks dominates the distribution of through-cracks. (4) Compared with the loss of mineral particles, the dissolution of cementation minerals is a more critical factor affecting the degradation of sandstone's mechanical properties.