A coupled humidity diffusion and swelling stress damage model with large deformation analysis and application in studying the swelling behaviors of skarn surrounding a tunnel

This study focuses on numerical modeling of the hygroscopic swelling behavior of skarn rock. A coupled midity diffusion and swelling stress damage model is proposed by integrating Fick's second law, the elastic theory and elastic damage mechanics. Geometric nonlinear algorithms are introduced into the model to characterize the swelling large deformation behavior of the skarn rock and varying swelling coefficient is also taken into account. The proposed model is subsequently implemented by the finite element method validated by comparing the simulated results with well-known analytical solutions, as well as experimental results. Taking a tunnel excavated from skarn rock as an example, the proposed model is applied to investigate the swelling behavior of the skarn rock in humid environments and discuss the effects of the dominant rameters on the swelling behavior. The proposed model can reproduce the swelling deformation and damage the skarn surrounding the tunnel, which demonstrates good agreement with the in situ monitoring