Numerical Simulation and Mechanism Analysis of Dissolution-Induced Spalling Damage in Grottoes

Dissolution-induced spalling is a major deterioration mechanism affecting the long-term stability of grottoes exposed to acidic environments. However, existing numerical methods have limited capability in capturing the coupled effects of hydrochemical dissolution, joint degradation, and fracture propagation. In this study, a hydrochemical damage-coupled Discontinuous Deformation Analysis (DDA) method is proposed. A mineral dissolution-based crack evolution model is first established, and a chemical residual strength factor Dc is introduced to quantify the degradation of fracture toughness, tensile strength, and shear strength. The factor is then incorporated into a nonlinear joint constitutive model to simulate the mechanical-chemical behavior. The proposed method is validated through a two-block contact model and a three-point bending test. Results show that the model accurately reproduces nonlinear contact behavior, including stiffness degradation, hysteresis, and peak strength reduction (24.6% after 90 days) under chemical erosion. Further application to a typical sandstone grotto reveals a progressive failure process characterized by crack initiation, propagation, coalescence, and eventual block detachment. The results demonstrate that hydrochemical dissolution significantly accelerates structural degradation of grotto rock masses, and that both the number of active cracks as well as the total crack length have significantly increased. The proposed method provides an effective tool for evaluating long-term stability and supports the preservation of grotto cultural heritage.