Behaviour of Square and Rectangular Tunnels Using an Improved Finite Element Method

Abstract

Due to its advantages (fast and accurate calculations), the Hyperstatic Reaction Method (HRM) was used to calculate the internal forces of circular tunnel linings in former works. This paper presents an improved HRM method that is developed to estimate the internal forces induced in square and rectangular tunnel linings. Based on the comparison of the internal forces induced in these linings obtained from the HRM method and the finite element method (FEM), the improved HRM method was validated. An extensive parametric analysis of the tunnel lining and ground parameters was then carried out using both the HRM and FEM. The results indicated a great influence of the lateral earth pressure coefficient K0, and the tunnel lining flexibility ratio F on the internal forces induced. Accordingly, the bending moments M, normal forces N, and shear forces T, induced in the tunnel lining decrease when the flexibility ratio of tunnel lining F increases. The maximum bending moment is observed at the tunnel sides that are perpendicular with the larger principal stress direction.