Numerical Simulation of Trapdoor Problem and Mitigation using Discrete Element Method (DEM)

The trapdoor problem is one of the ways to reproduce load transfers by the arching effect in a granular
layer in non-complex conditions. In addition, many analytical solutions for the prediction of load transfer mechanisms are based on the trapdoor problem. However, some of the parameters required are still being
widely discussed. In this study a numerical testing program was undertaken to investigate failure
mechanisms induced by the active movement of a deep rectangular trapdoor underlying a granular soil using discrete element method (DEM) by PFC2D software. Some models were used to evaluate the performance for mitigation of trap door problem using geogrids installed at different layers. The results of the numerical analyses were discussed and verified by previous experimental works. Finally, it was
concluded that using geogrids layers for mitigate this problem leads to additional confinement due to the
interlocking effect of installation this type of ground improvement and using of several layers of geogrids
at short distances leads to a significant reduction of displacements up to factor of 2.