Face stability analysis of large diameter shield tunnel in soft clay considering high water pressure seepage

Abstract

The aim of this paper is to study the influence of high water pressure seepage on the stability of large diameter shield tunnel face in soft clay. Based on allowable displacement rate field of the established double logarithmic spiral collapse body, the theoretical solution of limit support force of large diameter shield tunnel face under seepage was derived, the theoretical solutions of limit support force under different water levels were verified. And the influence of water levels and internal friction angles on the stability of large diameter shield tunnel face under seepage was also analyzed. The results show that the seepage force is the main part of the total limit support force. The influence of seepage on the stability of large diameter shield tunnel face in theoretical analysis can be regarded as seepage force on tunnel face and pore water seepage force in collapse body. The seepage effect in collapse body can be considered as the downward seepage in soil layer above the tunnel face, and the horizontal seepage in soil layer where the tunnel face is located. The influence of water levels and soil internal friction angles on the face stability is obvious when considering seepage effect.