Equivalent numerical simulation method and application in karst-induced collapse of overlying sandy stratum

Aiming at the karst-induced collapse of overlying sandy stratum, an equivalent numerical simulation method of karst-induced collapse is proposed in combination with the causation mechanism and physical model test result and applied in a project. The research results showed that: 1) The mechanism of karst-induced collapse of overlying sand layer is that the sand particles above fall into the karst cave and form a "funnel-shaped loose sand mass". 2) The equivalent numerical simulation method can calculate the volume of the loose sand mass by introducing sand loose coefficient and the physical model test of collapse angle in sandy stratum, which provides a new method for evaluating the disturbance analysis of karst-induced collapse of overlying sand layer. 3) For the applied project, the calculation results indicate that the karst-induced collapse of overlying sandy stratum has a greater impact on surrounding strata and segment lining structure when the tunnel is completely constructed.