Abstract
The objective was to optimize the existing solution for the limit support pressure of a tunnel face. Firstly, based on the numerical simulation results, the existing three-dimensional analytical solution for pore water pressure distribution is expanded to a three-dimensional solution considering the pore water pressure distribution in the upper formation behind the tunnel face. Then, according to the results of physical model tests, a failure model considering the failure range in the upper formation behind the tunnel face is established, and the newly established three-dimensional solution for pore water pressure is introduced into the model, and then the limit effective support pressure of the tunnel face considering seepage is obtained by the method of soil–water joint calculation. Finally, the calculation results in this paper are compared with the experimental results, numerical simulation results and existing theoretical solutions. The major findings are as follows. The distribution of pore water pressure in the front and back strata above the tunnel face is basically symmetrical. The limit effective support pressure of the tunnel face will increase linearly with an increase in the hydraulic head difference between the tunnel face and the ground surface. The calculated results of the new limit equilibrium theory are obviously larger than those of the existing theory and numerical simulation and closer to the results of the physical model tests. Therefore, the new limit equilibrium model can better predict the limit effective support pressure of the tunnel face considering seepage and provide a reference for actual projects.
Highlights
It is easy to form a seepage field near a tunnel face when the shield is excavated in a saturated sandy soil layer, which is not conducive to the stability of the tunnel face
Based on the results of physical model tests by Mi and Xiang [3], an instability failure model considering the failure range behind the tunnel face was established, and the newly established three-dimensional pore water pressure solution was introduced into the model to obtain the limit support pressure of the tunnel face
[3], aa failure failure model considering the failure range behind the tunnel face is established, the newly model considering the failure range behind the tunnel face is established, established the newly established three-dimensional solution for the pore water pressure is introduced into the model, and, the limit support pressure of the tunnel face is solved by the limit equilibrium method
Summary
It is easy to form a seepage field near a tunnel face when the shield is excavated in a saturated sandy soil layer, which is not conducive to the stability of the tunnel face. Perazzelli et al [11] and Cao et al [12] fitted the pore water pressure distribution expression based on the numerical simulation results and combined the classical wedge model to study the effect of seepage on the limit support pressure of the tunnel face. Lü et al [16], respectively, combined the seepage force and pore water pressure obtained from the numerical simulation results, and expressed the calculation of the limit support pressure of the tunnel face considering seepage. Based on the results of physical model tests by Mi and Xiang [3], an instability failure model considering the failure range behind the tunnel face was established, and the newly established three-dimensional pore water pressure solution was introduced into the model to obtain the limit support pressure of the tunnel face. The calculation results in this paper are compared with experimental results, numerical simulation results and existing theoretical solutions
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