Physical model tests and discrete element simulation of shield tunnel face stability in anisotropic granular media
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RESEARCH PAPER
Physical model tests and discrete element simulation of shield tunnel face stability in anisotropic granular media Xilin Lu¨1,2 • Sheng Zeng1,2 • Yucheng Zhao1,2 • Maosong Huang1,2 • Shaokun Ma3 • Zhiguo Zhang4 Received: 19 March 2020 / Accepted: 14 July 2020 Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The stability of excavation face in shield tunneling plays a key role for construction safety. The ignorance of soil anisotropy in most previous studies would induce inaccurate stability assessment. This paper studies the failure of shield tunnel face in cross-anisotropic granular media by physical model tests and discrete element simulation. Model tests were carried out on the tunnel face stability in anisotropic granular media, and initial anisotropy was generated by controlling the long axis of non-spherical particles. By conducting image analysis on the picture taken by HD camera, the failure mode of tunnel face was obtained. It consists of a sliding wedge and an overlying loosen area, and the inclination angle of sliding wedge varies with the bedding plane. The variation in limit support pressure with the intersection angle of the shield tunneling direction and the soil bedding plane was obtained. Discrete element simulation was further employed to study the tunnel face stability in cross-anisotropic granular media; the microscopic parameters were calibrated by fitting against the particle drop test and repose test. Clump particle consisted of three identical ball was used in the simulations, and its long and short axes were in accordance with rice particles. The obtained varying characteristic of limit support pressure with intersection angle from simulation is consistent with the test results, and the obtained failure mode is also similar to that of physical model test. The principal stress distribution at failure state was analyzed in the discrete element simulation, and the change of major principal stress direction from vertical to nearly horizontal in the loosen area clearly shows the formation of soil arches. Keywords Anisotropic soil Discrete element simulation Model test Shield tunnel face stability
1 Introduction The shield tunneling method is widely adopted in constructing underground facilities (i.e., subway tunnel, municipal pipeline, and oil storage tank) in soft ground
& Xilin Lu¨ [email protected] 1
Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China
2
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
3
College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, Guangxi, China
4
School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China
area. The maintenance of tunnel face stability plays a key role in safety during construction process; soil instability may induce strata collapse and adverse impact on adjac
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