Theoretical Analysis of the Joint Leakage in Shield Tunnel Considering the Typical Deformation Mode

Abstract

The joint leakage in a shield tunnel is a common defect and difficult to be accurately quantified due to the complex deformation mode and stress state, which seriously threatens the service performance of the tunnel lining. The waterproofing of the joint is divided into two stages, which are separately provided by the sealing gaskets in the joint and the normal stress on the joint interface. Combined with the two-stage characteristics of the joint waterproofing, an analytical leakage model is proposed to deal with the joint leakage. In this model, the maximum water head loss or critical water head flowing through the sealing gaskets is calculated by a general formula, in which the parameters are determined by indoor tests. The proposed analytical model for the joint leakage in the shield tunnel not only considers the joint deformation modes, including joint opening and joint dislocation, but also considers the stress state of the joint interface. The joint leakage analysis of a typical shield tunnel in Shanghai indicates that both the high external water head and the joint dislocation can reduce the critical joint opening of the initial leakage, and the critical joint opening of the waist joint is much smaller than that of the top joint. The average hydraulic pressure acting on the joint interface can be negligible, because it is less than 5% of the concrete stress at the joint. Based on the proposed joint leakage model, the waterproofing capacity of the tunnel-lining ring can be optimized by moving the sealing gaskets along the joint interface.