Predictive model for assessing the nonlinear surface displacement and mechanical response of shallowly buried tunnels under dip-slip fault dislocation

Abstract

The fault dislocation induces permanent ground surface displacement, leading to severe damage to tunnels. However, there is a notable scarcity of predictive models for nonlinear surface displacement and tunnel response under dip-slip fault dislocation. Previous analytical models have oversimplified surface displacement to a constant value. To this end, first, a predictive model for assessing the mechanical response of shallowly buried tunnels under dip-slip fault dislocation is established. Then, through a mathematical statistical analysis of field-measured data, a prediction method of nonlinear dip-slip surface displacement has been developed, and the nonlinear dip-slip surface displacement is introduced into the predictive model. The predictive model incorporates nonlinear surface displacement, fault zone width, and geometric nonlinearity, thereby markedly enhancing the accuracy of the calculation results. Secondly, the prediction model undergoes validation through experimental tests and numerical simulations, revealing a maximum error of 3.7 %. In contrast, neglecting nonlinear surface displacement can result in calculation errors as high as 517.5 %. Finally, the proposed predictive model is applied to conduct a parameter analysis, such as maximum surface displacement (Δ_dmax), dip angle (α), and fault zone width (W_F). The results shown that the maximum axial force (N_max), maximum shear force (V_zmax), and maximum bending moment (M_zmax) of the tunnel increase with the augmentation of Δ_dmax. For each incremental increase of 0.2 m in Δ_dmax, the N_max, V_zmax, and M_zmax exhibit an approximate increase of 22.1 %–100.3 %. The N_max and decreases with the increasing α, whereas both the V_zmax and the M_zmax increase as α rises. With each incremental increase of 10° in α, the N_max diminishes by approximately 16.1 %–49.2 %, while both the V_zmax and M_zmax experience an increase ranging from about 4.6 % to 19.1 %. An increase in W_F results in a decrease in the V_zmax and the M_zmax exerted on the tunnel. For every increment of 10 m in W_F, both the V_zmax and M_zmax decrease by approximately 15.8 %–32.3 %.