NUMERICAL ANALYSIS OF THE EFFECT OF EARTH PRESSURE BALANCED SHIELD TUNNELING ON SOIL STRESS-DEFORMATION BEHAVIOR

Abstract

 Three-dimensional (3D) finite element analysis programs are widely used for numerical simulation of tunneling with different degrees of approximation and various approaches. This study deals with the effects of earth pressure balanced (EPB) tunneling on the stress path and drainage condition of the soil during tunnel advancement. First, by using the Mohr-Coulomb criterion, the 3D stress distribution of the area near the crown and spring line of the tunnel is investigated, after which the tunnel stress path with respect to the Mohr-Coulomb yielding surface is presented. It was concluded that in the case of EPB shield tunneling, the soil around the cutter head tended to be in the elastic domain. Next, the effect of EPB tunneling on the drained and undrained behavior of the soil is examined. By taking into account the three significant factors of a) advance rate of the tunnel face, b) consolidation coefficient of the soil, and c) overburden depth of the tunnel, a parametric study is conducted and a numerical experimental equation proposed for determining drained or undrained soil condition during shield tunnel advancement. Finally, a case study of EPB tunneling is introduced. By using the case study data and results of EPB tunneling on stress path analyses, the proposed equation is verified.