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A Study of the Trapdoor Test of the Bolt-Support Effects
in a Soft Rock Tunnel
(1 Key Laboratory of Road and Traffic Engineering of the State Ministry of Education, Tongji University, Shanghai 200092;
2 Key Laboratory of Geotechnical and Underground Engineering, Ministry of Education, Tongji University, Shanghai 200092;
3 Yunnan Broadvision Engineering Consultants, Kunming 650011; 4 Shenzhen Traffic Utilities Construction Center, Shenzhen 518040; 5 Shanghai Municipal Engineering Design Institute Group Co. Ltd., Shanghai 200092)
Abstract Instability and even failure of surrounding rock are often caused by excessive rock deformation or local stress concentration when tunneling in soft surrounding rocks, and the anchor bolt is mainly used in practical engineering for initial support. Based on soft surrounding rock of grade IV, tunnel construction with bolt support was simulated by a similarity model test, and the progressive failure feature, failure mode of the surrounding rock, and supporting effects of an anchor bolt were studied. The results show that a stress disturbance area will be formed around the tunnel by excavation, but only a part of the disturbance area really will be damaged. Because of the support of the anchor bolt, rock damage on the crown presents a partitional failure mode, and the failure area of the rock is mainly concentrated in the sector formed by two tunnel sides with an angle of 45°+φ/2 to the horizontal plane. After excavation, a pressure-bearing arch, which is mainly located approximately 1.0-1.25B (B= tunnel span) away from the crown, is formed with increasing tangential stress of the rock mass above the crown.
Abstract：
Instability and even failure of surrounding rock are often caused by excessive rock deformation or local stress concentration when tunneling in soft surrounding rocks, and the anchor bolt is mainly used in practical engineering for initial support. Based on soft surrounding rock of grade IV, tunnel construction with bolt support was simulated by a similarity model test, and the progressive failure feature, failure mode of the surrounding rock, and supporting effects of an anchor bolt were studied. The results show that a stress disturbance area will be formed around the tunnel by excavation, but only a part of the disturbance area really will be damaged. Because of the support of the anchor bolt, rock damage on the crown presents a partitional failure mode, and the failure area of the rock is mainly concentrated in the sector formed by two tunnel sides with an angle of 45°+φ/2 to the horizontal plane. After excavation, a pressure-bearing arch, which is mainly located approximately 1.0-1.25B (B= tunnel span) away from the crown, is formed with increasing tangential stress of the rock mass above the crown.
XU Qian-Wei-1,
ZHU He-Hua-2,
DING Wen-Qi-2 etc
.A Study of the Trapdoor Test of the Bolt-Support Effects
in a Soft Rock Tunnel
[J] MODERN TUNNELLING TECHNOLOGY, 2014,V51(5): 108-113
2014, Vol. 51 