Three-dimensional analysis of effects of ground loss on static and seismic response of shafts

摘要

During the construction and use of underground structures, it is difficult to avoid ground loss. Previous studies suggested a correlation between ground loss and damage of underground structures. But the current studies are mainly focused on the two-dimensional analysis of tunnels. In the two-dimensional analysis, the simulation of ground loss is flawed, and the results cannot be applied to the shaft structures. Based on the Suzhou River deep underground drainage and storage system, this paper establishes a three-dimensional finite element model of the shaft. Voids of different depth, angle and location are set behind the shaft wall, and the effects of ground loss on static and seismic response of the shaft are analysed. It is found that the existence of ground loss leads to a stress concentration which changes the static deformation and internal force of the shaft. And large positive and negative bending moments occur in the circumference direction which may cause damage to the shafts. During the earthquake, the ground loss will increase the bending moments and reduce the axial pressure. But it has no significant effect on the response in the cross sections. This paper indicates that ground loss can change the static and seismic response of the shaft and it is a potential unsafe factor. Ground loss should be avoided as much as possible during shaft construction, and the impact of ground loss should be considered as appropriate in the design.