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Tunnel face stability model for layered ground with confined aquifers
Highlights Face stability model is formed for shield tunnel in ground with confined aquifers. Tunneling-induced seepage flow shows distinct pattern from that under phreatic water. Analytical seepage flow model is combined with a multilayer wedge mechanism.
Abstract Confined aquifers with high fluid pressures pose severe risks for the stability of the face of earth-pressure-balanced shields. This study presents a method to compute the limit face pressures in the layered ground with confined aquifers. Seepage analyses based on the finite element method (FEM) are conducted to investigate the underground water flow patterns in the above ground due to shield tunneling. These analyses show: the presence of confined aquifers enhances the hydraulic gradient around the tunnel face; the hydraulic heads display distinct distribution patterns in the confined aquifers and adjacent aquitards; the hydraulic gradients exhibit abrupt jumps at the aquifer-aquitard interface. These characteristics are in strong contrast to the distribution functions assumed in existing studies. Therefore, a new analytical flow model is proposed based on the hydraulic fields obtained from the seepage analyses. An approach to evaluate necessary face pressures is constructed by combining the flow model and a limit equilibrium model (LEM). By comparing against the results from drained FEM analyses under seepage flow, this paper shows that the proposed LEM can reasonably represent the influences of confined aquifers on the critical face pressures and the collapse mechanism of soils in front of the tunnel face.
Tunnel face stability model for layered ground with confined aquifers
Highlights Face stability model is formed for shield tunnel in ground with confined aquifers. Tunneling-induced seepage flow shows distinct pattern from that under phreatic water. Analytical seepage flow model is combined with a multilayer wedge mechanism.
Abstract Confined aquifers with high fluid pressures pose severe risks for the stability of the face of earth-pressure-balanced shields. This study presents a method to compute the limit face pressures in the layered ground with confined aquifers. Seepage analyses based on the finite element method (FEM) are conducted to investigate the underground water flow patterns in the above ground due to shield tunneling. These analyses show: the presence of confined aquifers enhances the hydraulic gradient around the tunnel face; the hydraulic heads display distinct distribution patterns in the confined aquifers and adjacent aquitards; the hydraulic gradients exhibit abrupt jumps at the aquifer-aquitard interface. These characteristics are in strong contrast to the distribution functions assumed in existing studies. Therefore, a new analytical flow model is proposed based on the hydraulic fields obtained from the seepage analyses. An approach to evaluate necessary face pressures is constructed by combining the flow model and a limit equilibrium model (LEM). By comparing against the results from drained FEM analyses under seepage flow, this paper shows that the proposed LEM can reasonably represent the influences of confined aquifers on the critical face pressures and the collapse mechanism of soils in front of the tunnel face.
Tunnel face stability model for layered ground with confined aquifers
Huang, Maosong (author) / Li, Yishan (author) / Shi, Zhenhao (author) / Lü, Xilin (author)
2022-12-12
Article (Journal)
Electronic Resource
English
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