Influence of tunnel shape on tunnel lining behaviour

Circular tunnels are the most popular shapes in urban underground transportation systems when mechanised tunnelling is used for the tunnel excavation. However, circular tunnels have a small space utilisation ratio. With materials development, non-circular tunnels are now common as their cross-section allows for an improvement in the efficiency of usage of underground space. In this work, the influence of tunnel shape on the lining forces was evaluated by using the hyperstatic reaction method (HRM). The internal forces derived using the HRM model were then compared with the results of a numerical model (Plaxis2D). A constant soil Young's modulus was adopted in both models. A parametric study was performed in order to assess the effect of parameters such as the Young's modulus of the soil, the lateral earth pressure coefficient, the tunnel lining thickness and tunnel depth on the structural forces produced in the tunnel lining.