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Discussion on Classification Method and Criterion for the Deep-buried and Shallow-buried Rock Tunnels
（1 Logistical Engineering University of PLA, Chongqing 401311；2 China Construction Tunnel Corp. Ltd., Chongqing 401147; 3 Air Force Engineering University, Xi′an 710038; 4 Fujian Minwu Great Wall Geotechnical Engineering Co., Ltd., Fuzhou 350012）
Abstract The traditional classification for the deep-buried and shallow-buried tunnels is based on the Protodya? konov′s pressure arch theory and not reasonable enough due to its limitation of this theory. In view of this the finite element limit analysis method was applied to the classification for the deep-buried and shallow-buried tunnels, and three principles were put forward. For the rock tunnel with surrounding rock of Ⅳ and Ⅴ, the classification for the deep-buried and shallow-buried tunnels is based on the failure modes of tunnel, it is defined as the shallow-buried tunnel if the fracture plane cuts through ground surface while it is defined as the deep-buried one if the fracture plane doesn′t cut through ground surface, the height of pressure arch of the shallow-buried tunnel obtained by using FEM strength reduction method can be taken as the dividing line for the shallow-buried and deep-buried tunnels.For the rock tunnel with surrounding rock of higher grade, the deep-buried and shallow-buried tunnels are defined according to the stability safety factor of the unlined tunnel, it is defined as the deep-buried tunnel when the stability safety factor is more than or equals 1.5 while the failure mode should also be considered to define them when the stability safety factor is less than 1.5. In addition, the division of deep-buried and shallow-buried tunnels should still consider the effects of environment, construction, geological structure, unstable block, which will cause the surrounding rock collapse and form loose pressure. At last, it is suggested that for the deep-buried and shallow-buried tunnels it can be calculated by elastic-plastic numerical analysis method, but for the shallow-buried tunnel it should also be analyzed according to the load-structure model to ensure safety.
Abstract：
The traditional classification for the deep-buried and shallow-buried tunnels is based on the Protodya? konov′s pressure arch theory and not reasonable enough due to its limitation of this theory. In view of this the finite element limit analysis method was applied to the classification for the deep-buried and shallow-buried tunnels, and three principles were put forward. For the rock tunnel with surrounding rock of Ⅳ and Ⅴ, the classification for the deep-buried and shallow-buried tunnels is based on the failure modes of tunnel, it is defined as the shallow-buried tunnel if the fracture plane cuts through ground surface while it is defined as the deep-buried one if the fracture plane doesn′t cut through ground surface, the height of pressure arch of the shallow-buried tunnel obtained by using FEM strength reduction method can be taken as the dividing line for the shallow-buried and deep-buried tunnels.For the rock tunnel with surrounding rock of higher grade, the deep-buried and shallow-buried tunnels are defined according to the stability safety factor of the unlined tunnel, it is defined as the deep-buried tunnel when the stability safety factor is more than or equals 1.5 while the failure mode should also be considered to define them when the stability safety factor is less than 1.5. In addition, the division of deep-buried and shallow-buried tunnels should still consider the effects of environment, construction, geological structure, unstable block, which will cause the surrounding rock collapse and form loose pressure. At last, it is suggested that for the deep-buried and shallow-buried tunnels it can be calculated by elastic-plastic numerical analysis method, but for the shallow-buried tunnel it should also be analyzed according to the load-structure model to ensure safety.
.Discussion on Classification Method and Criterion for the Deep-buried and Shallow-buried Rock Tunnels[J] MODERN TUNNELLING TECHNOLOGY, 2019,V56(1): 14-21
2019, Vol. 56 