Support pressure assessment of tunnels in the vicinity of leaking pipeline using unified upper bound limit analysis

Abstract

Pipeline leakage is a common phenomenon encountered in subway construction, which can happen before tunneling or may be induced by tunnel advancement. The strength deterioration of the surrounding soils and the downward seepage force caused by the infiltrated water will reduce the factors of safety of the tunnel. In the present work, a unified three-dimensional upper bound finite element method is established for support pressure assessment of tunnels around leaking pipelines. With the incorporation of suction stress-based effective stress of unsaturated soils, saturated and unsaturated soils could be simulated consistently. Two- and three-dimensional parameter analysis is conducted to study the evolution of limit support pressures and collapse mechanisms with the process of leakage. The effect of leaking location, ground water level, hydraulic properties, water pressure and axial length of leakage on the stability of surrounding tunnels is discussed in detail. It is shown that, the limit support pressure of the tunnel can increase rapidly after the occurrence of pipeline leakage, and a close correlation is found between the limit support pressure and the pore water pressure at the head of the tunnel.