Model test study on the deformation and failure mechanism of high-speed railway subgrade obliquely crossing ground fissure zones

Abstract

Ground fissure is a special geological disaster widely distributed around the world and occurs frequently in China. Questions about the influence of ground fissure activity on high-speed railway subgrade and whether the subgrade can cross a ground fissure zone are important issues in high-speed railway construction. To answer them, we conducted physical model test combined with numerical simulation of a high-speed railway subgrade obliquely crossing a ground fissure that allowed us to analyze the stress characteristics of the Cement Fly-ash Gravel (CFG) composite foundation subgrade, the structural deformation and damage, and the influence area of the subgrade under the influence of ground fissure. The results show that the head pressure of CFG piles in the hanging wall decreases with the increase of ground fissure dislocation but that the opposite in the footwall. The subgrade shows obvious uneven settlement deformation near the ground fissure, and as long as the ground fissure dislocation takes place, the reinforced concrete slab under the subgrade is compressed in the hanging wall and tensioned in the footwall. The deformation and failure of subgrade obliquely crossing ground fissure is tensile-bending failure mode. When the actual ground fissure dislocation reaches 0.8 m, the track bed gets destroyed; the reinforced concrete slab bends due to tensile failure; the CFG piles in the hanging wall cracks and tilts; and compression bending failure occurs in the footwall. This suggests that subgrade with a range of 32 m in the hanging wall and 16 m in the footwall need to be strengthened, and the high-speed railway should cross the ground fissure at as large an angle as possible.