Study on the micro-scale deformation and damage of cemented Xiyu conglomerate by coupled seepage-flow action

Xiyu conglomerate is widely distributed in Northwest China, which is a mud and calcium cemented pebble conglomerate formation, and its mechanical properties are severely weakened by cement content and seepage, posing a significant challenge to the safety of water conservancy and other engineering projects. Thus, this paper adopts the particle flow code (PFC3D) to establish a microscopic seepage-coupled uniaxial compression model, and validates the model's accuracy. The effects of seepage flow and cementation content on failure characteristics are analyzed in terms of deformation, uniaxial strength , and crack development. The results show that: (i) smaller seepage flow has less effect on the evolution of elastic modulus , Poisson's ratio and failure strain. The elastic modulus and Poisson's ratio decreased with increasing seepage flow rate, while the failure strain first increases and then decreases. Both the elastic modulus and failure strain decrease significantly with increasing cementation content, while Poisson's ratio increases significantly. (ii) The uniaxial strength decreases less when the seepage flow rate is low, while it generally decreases as the seepage flow rate increases. Uniaxial strength decreases significantly with increasing mud cementation content. (iii) Tensile and shear crack development is less affected by small seepage flow rates, while crack evolution becomes more significant as the seepage flow rate increases. Shear cracks decrease, tensile cracks increase, and the three-stage crack-vertical strain evolution becomes more pronounced due to the mud cementation content. The research findings provide a theoretical reference for related engineering projects. • Numerical analysis model of seepage-flow coupling of cemented rock masses was established from the microscopic scale. • The deformation and failure of Xiyu conglomerate under cementation content and seepage flow were analyzed in depth. • Seepage flow and cementation content significantly affect the deformation and crack development of Xiyu conglomerate. • The strength of the Xiyu conglomerate is weakened significantly by cementation content and seepage.