Three-dimensional stress-transfer mechanism and soil arching evolution induced by shield tunneling in sandy ground

• Published in: Tunnelling and underground space technology Vol. 93; p. 103104
• Main Authors: Lin, Xing-Tao, Chen, Ren-Peng, Wu, Huai-Na, Cheng, Hong-Zhan
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.11.2019; Elsevier BV
• Subjects: Earth pressure; Earth pressure balance shield (EPBS); Evolution; Excavation; Finite element analysis; Finite element method; Grouting; Mathematical models; Numerical modeling; Parameters; Soil analysis; Soil arching effect; Soil investigations; Soil settlement; Soil stresses; Soils; Stress redistribution; Subway construction; Subways; Three dimensional models; Tunneling; Tunneling shields; Tunnels; Underground construction; Underground structures; Changsha China; China; Numerical modeling; Stress redistribution; Earth pressure balance shield (EPBS); Soil arching effect
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2019.103104

•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. 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 0.73D (D = tunnel diameter) above the tunnel crown in vertical direction. The height of the arch zone above the loosened zone is about 1.27D. 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 0.6P1 − 2.2P1 and grouting pressure of 1.0P2 − 1.8P2, where P1 is initial horizontal stress at the tunnel axis and P2 = 1.2P1.