Influence of Weathering Cavities on the Structural Stability of the Yuanjue Grottos in Southwestern China Based on 3D Numerical Simulation

The Yuanjue Grottos are representative of the sandstone grottos in southwest China. The structural stability of their wallrocks has suffered a certain degree of damage, resulting from weathering cavities, which seriously threatens the long-term preservation of these cultural relics. This study utilizes 3D numerical simulation to assess the impact of weathering cavity depth on the structural stability of the grottos. The results reveal that the presence of cavities has led to significant wallrock deformation and settlement, particularly in the front side of the entrance and baseplate area. As the cavity depth increases, the deformation effect intensifies. This study also characterizes the relationship between stress deformation and the distribution of weathered fissures, indicating that joint areas are more susceptible to spalling. Displacement monitoring indicates that the baseplate has experienced uplift, followed by settlement as the cavity depth increases, suggesting an initial phase of elastic deformation followed by plastic and brittle deformation stages, which is consistent with the numerical simulation results. Notably, the baseplate’s settlement trend was found to accelerate when the cavity depth exceeded 4 m, with significant changes being observed when the depth exceeded 5 m. Therefore, the depth of the weathering cavity beneath the entrance of the Yuanjue Grottos should be controlled within 5 m, in order to ensure their long-term stability. This research contributes to the understanding of the mechanisms affecting the structural stability of grottos and provides valuable insights for conservation efforts.