A Calculation Method for Safety Distance Between the Confined Karst Cave and the Shield Tunnel Based on Upper Bound Theo
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ORIGINAL PAPER
A Calculation Method for Safety Distance Between the Confined Karst Cave and the Shield Tunnel Based on Upper Bound Theorem Quanwei Liu . Shangqu Sun . Hongbo Wang . Jixian Dong . Huanchun Hu
Received: 6 May 2020 / Accepted: 6 July 2020 Ó Springer Nature Switzerland AG 2020
Abstract As typical karst products, caves are highly concealed, thus resulting in the increase of rock permeability and the deterioration of rock mechanics. When the shield tunnel passes through karst area, the confined water cave near the excavation face can easily result in hazards such as water inrush, shield head drooping. Therefore, it is important to determine the critical safety distance between the karst cave and the shield tunnel. In this paper, a three-dimensional failure model was built when the karst cave was located in front of the tunnel. And then the corresponding analytical solution to the critical safety distance between regular karst cave and tunnel was deduced based on upper bound theorem of limit analysis. Additionally, the sensitivity curve of different parameters to critical safety distance was drawn by using the Matlab program, aiming to analyze the effects of rock mass parameters, karst cave parameters and geometric parameters on critical safety distance. Based on the optimizing dichotomy and rock mass instability criterion, the reliability of the above critical
Q. Liu Qingdao West Coast Rail Transit Co., Ltd., Qingdao, China S. Sun H. Wang (&) J. Dong H. Hu Shandong Provincial Key Laboratory of Civil Engineering Disaster Prevention and Mitigation, Shandong University of Science and Technology, Qingdao 266590, Shandong, China e-mail: [email protected]
safety distance formula was further verified by using COMSOL Multiphysics. The results confirmed that this method can provide reference for the design and construction of karst tunnel in the future. Keywords Shield tunnel Karst cave Upper bound theorem of limit analysis Critical safety distance Numerical verification
1 Introduction With the rapid development of cities and urban population, traffic congestion has become one of the greatest problems in most cities in China. Metro construction makes full use of underground space and reduces congestion on the ground, which has become the main form of urban infrastructure and traffic in China in the twenty-first century (Li et al. 2020a, b; Cui et al. 2015; Wang et al. 2017; Shen et al. 2014; Sun et al. 2020). By the end of 2019, a total of 6730.27 km of urban rail transit lines were in construction and operation in 40 cities. As one of the tunneling method, Shield tunneling has advanced mechanization and would cause little interference to urban ground traffic. Because of the advantage of safe, efficient and environment-friendly, it is now the preferred tunneling method in most cities. However, due to the complex urban geological conditions, a large number of metro tunnels run through karst geological areas. Most of the
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Geotech Geol Eng
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