Ground subsidence characteristics caused by construction of shallow-buried tunnel in a sandy soil composite formation
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ORIGINAL PAPER
Ground subsidence characteristics caused by construction of shallow-buried tunnel in a sandy soil composite formation Peng Zhang 1 & Yajing Pan 1 & Zhaocheng Yu 2 & Xiaoming Guan 1 & Gang Wang 1 & Jianyong An 3 & Haibo Lei 3 Received: 8 December 2019 / Accepted: 20 August 2020 # Saudi Society for Geosciences 2020
Abstract In dry fine sand and medium-coarse sand strata, large surface subsidence and even collapse are common issues related to tunnel excavation. In the Liu-Huo Section of Line 1 of Shijiazhuang Subway, transverse and vertical surface subsidence were examined by analyzing the measured subsidence data. The width coefficient of the settling tank and the loss rate of the sand mixed stratum were determined using the Peck formula. The settlement of the vertical and transverse surface and vault was further analyzed by establishing a three-dimensional numerical model of the tunnel. Results show that the deformation and surface subsidence vary rapidly for the dry sand mixed stratum, and the subsidence trough is “narrow and steep,” which is different from the general clay stratum. In the Peck formula, the ground settlement tank width coefficient is i = 6.55, and the formation loss rate is Vi = 4.81%. Ground settlement increased nonlinearly with the excavation of the pilot tunnels using the double-sided drift method. The settlement caused by the left No. 1 pilot tunnel was the largest, next was the right No. 3 pilot tunnel, the left No. 2 pilot tunnel, and the right No. 4 pilot tunnel. The settlement caused by the middle No. 5 and No. 6 pilot tunnels was smaller. The vertical settlement is divided into three stages: the small settlement stage, rapid stage, and stable stage. The settlement caused by the excavation of the No. 1, No. 2, and No. 3 pilot tunnels was the largest. After excavation of the No. 3 pilot tunnel, the settlement occupied about 78.3% of the final settlement. Monitoring of the No. 1, No. 2, and No. 3 pilot tunnels should be strengthened during the excavation, and the settlement should be strictly controlled. Keywords Sand mixed stratum . Shallow-buried subway tunnel . Double-sided drift method . Transverse surface subsidence . Vertical surface subsidence
Introduction With the rapid development of urban subways, surface subsidence disasters caused by subway construction are becoming more common. The study of strata deformation and surface Responsible Editor: Zeynal Abiddin Erguler * Peng Zhang [email protected] * Xiaoming Guan [email protected] 1
School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, China
2
Operating Branch, Qingdao Metro Group Co., Ltd, Qingdao 266000, China
3
China Construction Second Engineering Bureau Ltd, Beijing 100160, China
subsidence induced by urban large-section shallow-buried mined subway tunnels has been focused for many domestic and foreign scholars. The poor stability of sandy soil composite formations allows for the excavation of large-section shallow tunnels to cause disturbances, such as excessive surface subside
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