Three-dimensional stress-transfer mechanism and soil arching evolution induced by shield tunneling in sandy ground. (November 2019)

• Record Type: Journal Article
• Authors: Lin, Xing-Tao; Chen, Ren-Peng; Wu, Huai-Na; Cheng, Hong-Zhan
• Is Part Of: Tunnelling and underground space technology. Volume 93(2019)
• Publication Date: 2019-11
• Subjects: Earth pressure balance shield (EPBS) -- Numerical modeling -- Stress redistribution -- Soil arching effect; Tunneling -- Periodicals; Underground construction -- Periodicals; Tunnels -- Periodicals; Underground areas -- Periodicals; 624.193
• DOI: 10.1016/j.tust.2019.103104
• Languages: English
• ISSNs: 0886-7798

Abstract

Highlights: A method for determining the soil arching zone was proposed. The evolution of 3D soil arching zone during shield tunneling was revealed. The three-dimensional stress-transfer mechanism in soil arching zone during tunneling was disclosed. The effects of shield-driving parameters on the developments of loosened zone and soil arching zone were evaluated. Abstract: Tunnel excavation inevitably causes variations in stress and displacement fields in soil, which could affect the serviceability and safety of the adjacent underground structures. Change of the earth pressure acting on the existing structures is closely related to soil arching effect caused by a new tunnel excavation, but it is still lack of full understanding. In this study, a finite element method (FEM) model was first verified by field measurements based on a case history of Metro Line 2 construction in Changsha, China. Then, a series of simplified three-dimensional (3D) FEM models were established to investigate the stress redistribution and the soil arching evolution induced by earth pressure balance shield (EPBS) tunneling. The changes of the earth pressure, the coefficient of lateral earth pressure, and the settlement of soil mass above the tunnel during tunneling were analyzed and the soil arching zone was determined. 3D stress-transfer mechanism in soil arching zone during tunneling was revealed. In addition, the influences of shield-driving parameters (i.e. support pressure, grouting pressure) on soil arching evolution were also investigated. The results show that the loosened zone extends to nearly 0.73 D ( D = tunnel diameter) above the tunnel crown in vertical direction. The height of the arch zone above the loosened zone is about 1.27 D . The horizontal soil arching in front of EPBS occurs near the ground surface. With EPBS advancing, the horizontal soil arching gradually transforms into the vertical soil arching. After the installation of lining, the earth pressure is finally mainly transferred by vertical soil arching in the transverse section. The proper combination of shield-driving parameters for controlling the expansion of the loosened zone is support pressure of 0.6 P 1 − 2.2 P 1 and grouting pressure of 1.0 P 2 − 1.8 P 2, where P 1 is initial horizontal stress at the tunnel axis and P 2 = 1.2 P 1 .