Undrained stability of active trapdoors in two-layered clays

Several environmental changes can induce an underground hole, leading to failures of non-ground infrastructure, such as pavements. Under a continued overload of traffic action on the pavement, the hole can potentially collapse, leading to creation of potholes. This phenomenon is commonly known as a trapdoor problem. Even though there are several previous works considering this problem, the stability solutions of trapdoors in two-layered soils have not yet been studied. To estimate the undrained stability of active trapdoors in two-layered clays under plane strain conditions, numerical solutions based on the finite element method have been developed. The influence parameters include the coverage depth of the trapdoor, and the thickness and undrained shear strength of the clay layers. The effects of these parameters on the stability of active trapdoors as well as their associated failure mechanisms are examined and discussed in this paper. The solutions are presented in the form of dimensionless charts that can be used for the design of trapdoor systems in two-layered clays with different thicknesses and undrained shear strengths.