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Theoretical Analysis of the Stability of Tunnel Face under Pipe Roof Presupport
(1 Hunan University of Science and Technology, Xiangtan 411201; 2 China Construction Tunnel Corp., Ltd., Chongqing 401320;3 China Railway 16th Bureau Group Road and Bridge Engineering Co., Ltd., Beijing 101500)
Abstract In order to investigate the stability of the tunnel face under pipe roof support, this paper takes into con? sideration the stress characteristics of the pipe roof, establishes a Winkler foundation model for the pipe roof, and applies the foundation reaction force on the upper part of the tunnel face in the model. Meanwhile, based on the rigid limit equilibrium theory, this paper derives the calculation formula of the safety coefficients for the stability of the tunnel face. Finally, taking the No. 3 transverse adit of Badong tunnel as the engineering background, this paper analyzes the stability of the tunnel face with and without the pipe roof, and discusses the effect law of each parameter on the deflection of the pipe roof and the stability of the tunnel face. The results show that the maximum deflection of the pipe roof and the displacement near the tunnel face will decrease and the safety factor for the stability of the tun? nel face will increase, as the diameter of the pipe roof increases, the displacement of the support at the end of the pipe roof decreases, the advance per round and the height of excavation bench decrease, and the internal friction angle and cohesion of the surrounding rock increase; shorter advance length has more obvious effect on improving the stability of the tunnel face under better surrounding rock conditions, lower excavation heights and smaller pipe roof support displacements; as the tunnel buried depth increases, the safety factor for the stability of the tunnel face first decreases before it increases, and then remains constant. This is related to the calculation formula for the surrounding rock pressure specified in the code, for a shallow buried tunnel, the larger the buried depth, the larger the load; for a tunnel located between the deep buried depth and shallow buried depth, due to the existence of the confining effect from both sides of the surrounding rocks, the surrounding rock pressure will decrease when the buried depth increases; for a deep buried tunnel, the load will remain constant due to the collapse arch effect.
Abstract：
In order to investigate the stability of the tunnel face under pipe roof support, this paper takes into con? sideration the stress characteristics of the pipe roof, establishes a Winkler foundation model for the pipe roof, and applies the foundation reaction force on the upper part of the tunnel face in the model. Meanwhile, based on the rigid limit equilibrium theory, this paper derives the calculation formula of the safety coefficients for the stability of the tunnel face. Finally, taking the No. 3 transverse adit of Badong tunnel as the engineering background, this paper analyzes the stability of the tunnel face with and without the pipe roof, and discusses the effect law of each parameter on the deflection of the pipe roof and the stability of the tunnel face. The results show that the maximum deflection of the pipe roof and the displacement near the tunnel face will decrease and the safety factor for the stability of the tun? nel face will increase, as the diameter of the pipe roof increases, the displacement of the support at the end of the pipe roof decreases, the advance per round and the height of excavation bench decrease, and the internal friction angle and cohesion of the surrounding rock increase; shorter advance length has more obvious effect on improving the stability of the tunnel face under better surrounding rock conditions, lower excavation heights and smaller pipe roof support displacements; as the tunnel buried depth increases, the safety factor for the stability of the tunnel face first decreases before it increases, and then remains constant. This is related to the calculation formula for the surrounding rock pressure specified in the code, for a shallow buried tunnel, the larger the buried depth, the larger the load; for a tunnel located between the deep buried depth and shallow buried depth, due to the existence of the confining effect from both sides of the surrounding rocks, the surrounding rock pressure will decrease when the buried depth increases; for a deep buried tunnel, the load will remain constant due to the collapse arch effect.
AN Yonglin1 LI Jiahao1 OUYANG Pengbo2 LIU Wenjuan1 SU Guangming3 ZHOU Jian3
.Theoretical Analysis of the Stability of Tunnel Face under Pipe Roof Presupport[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(3): 115-122
2021, Vol. 58 