Research on the design method and disaster reduction effect of articulated variable cross-section for sandy tunnel under the action of bedrock normal fault dislocation

Tunnel structures that pass through active faults are prone to serious damage under the action of fault displacement. When the tunnel cannot avoid active faults, a series of disaster reduction measures need to be taken to reduce the impact of fault displacement on the tunnel. In current work, firstly, a three-dimensional numerical analysis model was established, and the numerical model was validated through existing centrifugal model experiments. Then, by comparing the damage response of articulated tunnels and integral tunnels under fault action, the energy dissipation mechanism and disaster reduction effect of articulated design method were researched, and the key parameters in the articulated design method, such as the longitudinal position, elastic modulus and length of flexible joint and the length of lining segment, were further analyzed for their influence on the disaster reduction effect. Finally, considering the possibility of groundwater seepage during tunnel operation in areas with abundant water, a variable cross-section disaster reduction method based on the articulated design was proposed, and the disaster reduction effect under different parameter influences were discussed. This work can provide meaningful references for the disaster reduction design method of sand tunnels under the action of bedrock normal fault dislocation.