Limit support pressure of tunnel face in multi-layer soils below river considering water pressure

Abstract

This paper presents a method to determine the limit support pressure of tunnel face in multi-layer soils below river considering the water pressure. The proposed method is based on the 3D Terzaghi earth pressure theory and the wedge theory considering the water pressure. The limit support pressures are investigated using the limit equilibrium method and compared to those calculated using a numerical method, such as FLAC3D. Four cases focusing different combinations of three layers are analyzed. The results obtained by the numerical method agree well with the predictions of the proposed limit equilibrium method. The limit support pressure obtained using the limit equilibrium method is greater than that obtained by the numerical method. The limit equilibrium method is safe and conservative in obtaining the limit support pressure. The proposed limit equilibrium method is expected to be easily adaptable and to enhance the reliability of tunnel design and construction in multi-layer soils below river.