A study on arching mechanism in trapdoor model test and equivalent discrete element simulations

The complex interaction of underground structures with the surrounding soil has long been studied due to their importance in practical geotechnical engineering. Prior researchers have reported that the stress distribution on a buried structure varies sensitively with the settlement of surrounding subsoil. However, certain soil parameters influencing the soil-structure interaction need to be clarified. In this contribution, trapdoor model tests using a soil box with multiple movable base plates mounted with load cells were conducted. Spherical glass beads were used as analogue to soil particles to assess fundamentals of arching resistance mechanism. To understand particle scale responses during the trapdoor test, the discrete element method (DEM) simulations were also performed. In the numerical DEM analyses spherical particles with the equivalent diameter range and the material properties were considered for better comparison. It was found that the earth pressure distribution varies with varying height to width (H/B) ratio, and arch formation is observed with increasing the H/B value. Arching action is further confirmed by evaluating the shear stress distribution on the base plates and the surface settlement of the model ground. These observations are in good agreement between experiments and DEM analyses.