Water-rock interaction-induced degradation of Jinping marble in in-situ environments: A multi-scale analysis of mechanical behavior

Abstract

In deep engineering practices, surrounding rocks are often subjected to long-term interactions between high pore pressure and high geostress environments, necessitating a thorough understanding of water-rock coupling effect under in-situ conditions. This study investigates these interactions by replicating the deep, high-pressure environment of China Jinping Underground Laboratory (CJPL) through a specially designed high-pressure water-rock coupling apparatus. The research focuses on Jinping marble, conducting in-situ stress saturation treatments under varying solvent pH conditions (7, 8, and 9) and exposure durations (1 d, 23 d, 60 d, and 100 d) at a simulated depth of 2400 m. Extensive macroscopic and microscopic mechanical tests on the treated samples reveal significant time-dependent degradation in key mechanical parameters, including fracture toughness, hardness, and deformation modulus, with the initial decline being more rapid. The fracture surfaces of rock samples treated with pressurized saturation predominantly exhibit transgranular fractures, with intergranular fractures as secondary features. The observed water-rock coupling effects arise from both physical and chemical mechanisms. Notably, within the pH range of 7–9, rock samples treated with a neutral solvent show a more pronounced deterioration trend compared to those treated with an alkaline solvent. Complementary in-situ water analysis from Jinping Mountain further indicates that high confining pressure substantially restricts water infiltration in deep environments. These insights advance the theoretical foundation for safe and effective deep engineering practices.