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A Study of the Dynamic Response Characteristics of a Tunnel Structure Through an Interface of Soft and Hard Rock
(1 Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031;2 Guangzhou Metro Design and Research Institute Co. Ltd., Guangzhou 510308; 3 Fujian University of Technology, Fuzhou 350014)
Abstract Tunnel portal sections passing through an interface of hard and soft rock are vulnerable to severe damage at this high intensity seismic area. Based on the Longxi tunnelon the Chengdu-Wenchuan expressway, the earthquake dynamic response of a tunnel portal structure was analyzed using the numerical simulation method for various inclination angles of the soft/hard rock interface. The results show that: 1) the relative displacement of the tunnel lining structure increases obviously during a strong earthquake when the tunnel structure passes through the interface between soft and hard rock, and the relative displacement of the tunnel lining in the diagonal direction is higher than the relative horizontal displacement at the tunnel crown and invert; 2) the relative displacement of the tunnel structure at the soft-rock side of the interface increases with the decrease of the inclination angle, while the earthquake motion has little influence on the tunnel structure deformation at the hard-rock side; and 3) under an inclination angle ＜45°, the earthquake motion has a crucial influence on the safety of the upper tunnel structures (crown and spandrel) with some safety factors being less than 1, and under an inclination angle ＞45°, the seismic motion has a significant effect on the lower part of the tunnel structure (invert and arch springing).
Abstract：
Tunnel portal sections passing through an interface of hard and soft rock are vulnerable to severe damage at this high intensity seismic area. Based on the Longxi tunnelon the Chengdu-Wenchuan expressway, the earthquake dynamic response of a tunnel portal structure was analyzed using the numerical simulation method for various inclination angles of the soft/hard rock interface. The results show that: 1) the relative displacement of the tunnel lining structure increases obviously during a strong earthquake when the tunnel structure passes through the interface between soft and hard rock, and the relative displacement of the tunnel lining in the diagonal direction is higher than the relative horizontal displacement at the tunnel crown and invert; 2) the relative displacement of the tunnel structure at the soft-rock side of the interface increases with the decrease of the inclination angle, while the earthquake motion has little influence on the tunnel structure deformation at the hard-rock side; and 3) under an inclination angle ＜45°, the earthquake motion has a crucial influence on the safety of the upper tunnel structures (crown and spandrel) with some safety factors being less than 1, and under an inclination angle ＞45°, the seismic motion has a significant effect on the lower part of the tunnel structure (invert and arch springing).
SHEN Yu-Sheng-1,
ZOU Cheng-Lu-2,
JIN Zong-Zhen-3 etc
.A Study of the Dynamic Response Characteristics of a Tunnel Structure Through an Interface of Soft and Hard Rock[J] MODERN TUNNELLING TECHNOLOGY, 2015,V52(3): 95-102
2015, Vol. 52 