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Cause Analysis and Treatment Measures of a Collapse Event for a ShallowBuried Mountain Tunnel in Soft Rock
(1 Jincheng College of Sichuan University, Chengdu 610071; 2 Power China Chengdu Engineering Corporation Limited, Chengdu 610072; 3 Port and Channel Shandong Engineering Company, Shandong Luqiao Group Co. Ltd., Jinan 250021)
Abstract Based on a shallow-buried mountain tunnel in soft rock, the causes of a tunnel collapse in soft rock are analyzed and summarized. It is concluded that: 1) the index of allowed blasting vibration velocity of 10 cm/s is too large for soft rock mountain tunnels, and repeated blasting vibrations will exceed the tolerance value of the rock blasting vibration during excavation by steps; and 2) the frequency of monitoring and measuring should vary with changes to the tunnel construction method, which is necessary to establish a dynamic warning system for tunnel collapses. The blasting vibration velocity of a mountain tunnel in soft rock can be controlled more effectively using the general principles of stabilizing the collapse cavity, filling the collapse cavity, advance grouting of the collapse cavity and cautious passage. The blasting vibration velocity can be reduced by using different arrangements of drill holes at various sections, simultaneous initiation and millisecond delay initiation, which will facilitate rapid passage in the soft rock section.
Abstract：
Based on a shallow-buried mountain tunnel in soft rock, the causes of a tunnel collapse in soft rock are analyzed and summarized. It is concluded that: 1) the index of allowed blasting vibration velocity of 10 cm/s is too large for soft rock mountain tunnels, and repeated blasting vibrations will exceed the tolerance value of the rock blasting vibration during excavation by steps; and 2) the frequency of monitoring and measuring should vary with changes to the tunnel construction method, which is necessary to establish a dynamic warning system for tunnel collapses. The blasting vibration velocity of a mountain tunnel in soft rock can be controlled more effectively using the general principles of stabilizing the collapse cavity, filling the collapse cavity, advance grouting of the collapse cavity and cautious passage. The blasting vibration velocity can be reduced by using different arrangements of drill holes at various sections, simultaneous initiation and millisecond delay initiation, which will facilitate rapid passage in the soft rock section.
.Cause Analysis and Treatment Measures of a Collapse Event for a ShallowBuried Mountain Tunnel in Soft Rock[J] MODERN TUNNELLING TECHNOLOGY, 2018,V55(2): 201-207
2018, Vol. 55 