Numerical study on tunnel deformation under local thickness reduction in tunnel linings and destruction prediction

The cavity area commonly appears in lining structures in engineering practice, which has great influences on the long-term stability of tunnel operation. In order to investigate the influences of thickness reduction of lining structures on displacement and mechanical characteristics of tunnels, 1000 groups of numerical simulations with different buried depths, angles of local thickness reduction location, reduction lengths and thicknesses of linings of tunnel the conducted. Through analysis of the numerical simulation results, it can be concluded that the local thickness reduction area has less influences on displacement. Tthe maximum compressive stress of the tunnel is mainly concentrated at the left and right arch feet of the tunnel, and local thinning at the right side of the tunnel is prone to causing stress concentration at the left arch feet of the tunnel. Local thinning of linings may cause tensile stress concentration at the left and right arch feets, while under more conditions, local thinning of linings may cause tensile stress concentration near the local thinning area. The tensile stress concentration mainly occurs at the left and right arch feets and near the thinning area. Based on the 1000 groups of numerical simulation results, the CART tunnel damage predictive model is established. Meanwhile, 2 numerical examples verify the validity of the predictive model. This study provide numerical simulation basis for the mechanical and stability analysis of tunnels under local thickness reduction.