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

Abstract

This study focuses on numerical modeling of the hygroscopic swelling behavior of skarn rock. A coupled humidity diffusion and swelling stress damage model is proposed by integrating Fick’s second law, the humid-elastic theory and elastic damage mechanics. Geometric nonlinear algorithms are introduced into the coupled 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 and 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 parameters on the swelling behavior. The proposed model can reproduce the swelling deformation and damage of the skarn surrounding the tunnel, which demonstrates good agreement with the in situ monitoring results. Moreover, the damage evolution of the skarn rock induced by humidity diffusion exhibits stepped growth due to the accumulation of swelling stress. The proposed coupled model provides a novel tool for the design and analysis of underground engineering constructions in swelling rocks under humid conditions.