Discrete Element Investigation of the Role of Relative Density in Soil Arching Phenomena

Discrete element method (DEM) simulations are performed to investigate the role of relative density in developing soil arching in an assemblage of particles due to downward trapdoor displacement. The effects of relative density are investigated with different trapdoor widths and soil heights, and further investigation is made into the role of particle nonsphericity and contact friction on the observed effects. DEM enables investigation of the reduction of normal stress on the trapdoor, force chain networks, and particle kinematics affecting the soil’s volumetric and shear responses to the trapdoor displacement. Dilation of the granular media during shear affects the deformation mechanisms that develop due to trapdoor displacement. Dense soil dilates and expands to fill in the space created by trapdoor movement, which minimizes the surface manifestations of trapdoor displacement. Narrower trapdoors produce smaller ground surface settlements and greater load reduction on the trapdoor. An analysis of the force chains that develop in an arc above the trapdoor shows shear stresses increase in the soil above the trapdoor as the net confining stress decreases. The initial development of the arc pattern within the soil depends greatly on relative density. Inevitably, the arc collapses and two arcs develop at large trapdoor displacements regardless of the soil density.