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Model Experiment and Numerical Simulation of Characteristics of Stress Disturbance Induced by Tunnel Excavation in a Soft Rock Mass
(1 Key Laboratory of Road and Traffic Engineering of Ministry of Education, Tongji University, Shanghai 201804; 2 Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092; 3 The Second Engineering Co. Ltd. of China Railway Seventh Group, Xi′an, Shanxi 710032)
Abstract Based on the Wuning-Ji′an highway tunnel projects, and taking soft and fractured rock masses as a research object, model experiments and numerical simulations were conducted to study the progressive failure mecha?
nism and the stress development sequence of surrounding rock, with and without faults, above the tunnel crown, providing a reference for the prevention of collapse and the design of lining structures. Research results show that: 1)shear failure of the rock mass often occurs below the tunnel haunch after tunnel excavation due to highly concentrated stress; 2) in a tunnel with faults, the rock mass below the fault can be placed in a cantilevered state and is prone to tension and shear failure; 3) the influence zone caused by tunnel excavation is mainly located between two inclined planes starting from the arch springline with an angle of 45°+φ/2 to the horizontal plane—the collapsed rock mass only accounts for a small part of this affected area; 4) due to the existence of the fault, the radial stress in the rock mass above the tunnel crown is reduced after excavation, and the scope of such stress reduction is larger than if
there is no fault; and 5) the tangential stress concentration of the rock mass above the tunnel crown gradually develops from the tunnel perimeter towards the outside, accompanied by rock cracking and collapse when there is no fault; the concentration of tangential stress occurs at a farther position from the crown when there is a fault.
Abstract：
Based on the Wuning-Ji′an highway tunnel projects, and taking soft and fractured rock masses as a research object, model experiments and numerical simulations were conducted to study the progressive failure mecha?
nism and the stress development sequence of surrounding rock, with and without faults, above the tunnel crown, providing a reference for the prevention of collapse and the design of lining structures. Research results show that: 1)shear failure of the rock mass often occurs below the tunnel haunch after tunnel excavation due to highly concentrated stress; 2) in a tunnel with faults, the rock mass below the fault can be placed in a cantilevered state and is prone to tension and shear failure; 3) the influence zone caused by tunnel excavation is mainly located between two inclined planes starting from the arch springline with an angle of 45°+φ/2 to the horizontal plane—the collapsed rock mass only accounts for a small part of this affected area; 4) due to the existence of the fault, the radial stress in the rock mass above the tunnel crown is reduced after excavation, and the scope of such stress reduction is larger than if
there is no fault; and 5) the tangential stress concentration of the rock mass above the tunnel crown gradually develops from the tunnel perimeter towards the outside, accompanied by rock cracking and collapse when there is no fault; the concentration of tangential stress occurs at a farther position from the crown when there is a fault.
XU Qian-Wei- 1 Cheng-Pan-Pan- 1 Zhu-He-Hua- 2 Ding-Wen-Qi- 2 Chen-Guo-Zhong- 3
.Model Experiment and Numerical Simulation of Characteristics of Stress Disturbance Induced by Tunnel Excavation in a Soft Rock Mass[J] MODERN TUNNELLING TECHNOLOGY, 2016,V53(6): 154-164
2016, Vol. 53 