Analytical approach for determining the response of a tunnel structure crossing a reverse active fault

In practical scenarios, tunnels may unavoidably cross active fault zones, leading to potentially severe damage by active fault displacement during earthquakes. Previous studies have failed to clearly establish an analytical method that considers both compressive and frictional behavior between tunnels and the soil that surrounds them, hindering the understanding of the tunnel -soil interaction. To address this, a finite element model (FEM) has been developed in this study to investigate the compressive and frictional characteristics of the tunnel -soil interaction of a reverse active fault -crossing tunnel. The model identifies six distinct zones of tunnel -soil interaction, namely, two "active" zones, two "passive" zones, and two "separation" zones. Building on these findings, the active fault -tunnel system was divided into three equivalent sub -systems, and an analytical method was established by creating and then combining equations for each sub -system. By applying the Pasternak Elastic Foundation Beam theory and Elastic theory, an analytical method is introduced that can simultaneously consider the distributed non-linear compressive interactive stress and non-linear frictional interactive stress. The results of the analytical method were validated with the FE results under three series of geological conditions. Through a quantitative examination of the similarity ratio and length of influence, the analytical results were seen to effectively reflect the characteristics of the soil -tunnel interaction and exhibit a good agreement with the FE results. It is concluded that the analytical model will serve as a computational reference for the design of reverse active fault -crossing tunnels.