Stability analysis of earth pressure balance shield tunnel face considering soil arching

Abstract

Face stability in tunnels excavated under pressurised shields in compound strata is a major issue in tunnelling projects. An analytical method is proposed to predict the horizontal earth pressure at the tunnel face of an earth pressure balance shield in compound strata using a silo–ring model. Three-dimensional arching effects and the friction between cutter plates are considered in the method. The fourth-order Runge–Kutta method is used to evaluate the horizontal earth pressure of loosening soil in the quarter-ring body on the cutter plates. The method can be used to evaluate the horizontal soil pressure at a tunnel face in compound strata and to predict the most vulnerable area during excavation. A parameter study was conducted to assess the influence of soil cohesion and friction angle on the horizontal soil pressure. It was found that the friction angle has more apparent influence than cohesion. A comparison of results indicated that the proposed method is in generally good agreement with field-observed behaviour and the results calculated using other approaches.