Ground Behaviour above Tunnels in Sand - DEM Simulations versus Centrifuge Test Results

The paper evaluates the effectiveness of the discrete element method in estimating the shape of settlement troughs above tunnels in sand. Results of a DEM model are compared against data obtained from a centrifuge test which modelled the tunnel volume loss process within sand. The centrifuge data is based on PIV analysis, which allows insight into soil displacement with depth. Overall, fair to good agreement was obtained between the DEM and centrifuge models. Several interesting observations are noted in both the DEM and the centrifuge models: (1) the normalised tunnel collapse pressure is higher than that obtained using standard upper and lower bound solutions; and (2) the width of the surface settlement trough decreases with tunnel volume loss.