Abstract:

A largediameter slurry shield used in Mawan subsea tunnel continuously crosses through fullface soft stratum, uppersoft and lowerhard strata, and fullface slightlyweathered rock stratum. To investigate the influence of slurry pressure of slurry shield on face stability under complex strata conditions, 3D numerical simulation models under different strata are established to obtain corresponding displacement distribution laws and ultimate minimum supportstress ratio of tunnel face. In addition, the rectangular load mode is often used to simplify the slurry pressure in previous researches, the differences between the actual trapezoidal load mode and the simplified rectangular load mode in the stability analysis of tunnel face are compared and analyzed. The results show the following. (1) In the case of fullface soft stratum, the displacement of the tunnel face is relatively uniform in the middle of tunnel face, while it is quite different at both ends, whereas in the uppersoft and lowerhard strata, the displacement decreases linearly from the arch crown to the bottom. (2) The maximum supportstress ratio of the tunnel face obtained by tangent intersection method is the largest in the fullface soft stratum, followed by that in uppersoft and lowerhard strata, and that in the fullface slightlyweathered rock stratum is the smallest. (3) In the case of trapezoidal load distribution, both the upper soil displacement and the obtained ultimate minimum support stress ratio are far larger than that of rectangular load distribution, indicating that it is unreasonable to ignore the influence of unit weight of slurry in calculation.

Key words: large-diameter slurry shield tunnel, face stability, slurry pressure, complex strata, numerical analysis