Using the discrete element method (DEM), the particle flow of dry sand with friction angle of 37 degree and progressive failure in a tunnel workface under three cover depths were simulated to examine the limit support pressure of workface and ground turbulence in sandy ground. These simulations resulted in three main findings. First, under different cover depths, the support pressures evolve to limit values when workface displacement reaches 6%D (D is the diameter of the tunnel), and the corresponding limit support ratio is 10% to 20%; the softening effect of sand after peak strength enlarges the final limit support pressure. Second, severe ground disturbance is triggered when the support ratio is reduced to 40% to 50%, and the disturbance degree and range are sensitive to cover depth: the disturbance range and degree triples and doubles, respectively, when cover drops to 0.5D from 2D. Significant ground settlements occur when the support ratio drops to 40% to 50%. Third, based on deformation control, the support ratio is 40% to 50%, which is much smaller than that basedon limit failure; by taking into consideration both tunneling efficiency and cutters’ wear, it is rational to drop the support ratio to 40% to 50%.

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