Abstract: Aiming at seepage-mechanical instability caused by the weakening of Xiyu conglomerate when it meets water, we conduct seepage dissolution tests and mechanical tests on the conglomerate under different seepage pressures－for the Momoke water control project in Kashgar, Xinjiang－focusing on the influence of seepage pressures and loading paths on the seepage characteristics and strength evolution of rock mass. The results show time variations in permeability coefficients feature two stages: In initial stage, the water absorption and expansion of clay minerals lead to a sudden drop in the rock mass￠s permeability (41% - 52% within 48 h at 0.05 MPa); in later stage, dissolution of its calcium cement leads to significant adjustment in its pore structure with permeability approaching a stable value (2.40 - 6.45 mD). Variations in calcium ion concentration confirms the characteristics of water-rock reaction in the two stages. Direct loading causes a sudden drop in the conglomerate￠s permeability and a continuous damage to its structure, while step-by-step loading promotes its dynamic pore erosion-siltation balance, resulting in a smaller attenuation range of its mechanical parameters. The coupling effect of infiltration and dissolution generates nonlinear deterioration in the conglomerate￠s mechanical properties, and an increase in infiltration pressure causes a nonlinear decrease in a number of its parameters－such as compressive strength, elastic modulus, residual strength, and tensile strength. Damage to its microstructure makes the failure mode shift from brittle splitting to tensile-shear composite failure. This study lays a basis of multi-field coupling analysis for stability prediction of Xiyu conglomerate strata.

Key words: Xiyu conglomerate, infiltration and dissolution, compressive strength, permeability, failure mode