Numerical investigation of anisotropic and time-dependent behaviors of tunnel invert structure in layered rock mass

Abstract

In this paper, the bottom of the tunnel structure is uplifted with time under the condition of layered surrounding rock, and the influence of the change in slope angle on the bottom uplift is discussed. In addition, the finite difference method is used to simulate the limitation of the uplift deformation of the tunnel bottom structure by adjusting the rise span ratio of the inverted arch. The conclusions are as follows: (1) The “weak plane” in layered rock mass produces anisotropy of deformation. The creep speed of the surrounding rock is fast at the initial stage and then stabilizes after a certain period. (2) With different dip angles of the layered rock mass, the peak vertical displacement of the inverted arch filling layer is accordingly affected by the dip angle. (3) In engineering, the method of adjusting the rise span ratio to increase the depth of invert is usually applied to restrain the uplift deformation of invert structure. According to the numerical analysis results, with the increase in depth, the deformation inhibition capability does not become stronger. In addition, a similar situation occurs in the plastic zone of the filling layer. Thus, the rationality of deepening depth should be fully considered when adjusting the rise span ratio. This paper analyzes the numerical simulation of the tunnel substructure of a layered rock tunnel with time effect to provide a useful reference for the tunnel design under such surrounding rock conditions.