Application of Displacement Direction Angle Theory on Excavation Methods Conversion Opportunity of Zi-Zhi Tunnel
Stratum in shallow buried excavation section of Zi-Zhi Tunnel is generally upper-soft and lower-hard. To reduce the rock disturbance and ensure the construction progress, excavation method conversion from Cross Diaphragm with Step method to bench method should be conducted ahead of schedule. To determine the excavation methods conversion opportunity, considering different positions between tunnel face and the interface of stratum, based on displacement direction angle theory, the change laws for the displacement direction angle and three-dimensional deformation of surrounding rock under different conditions were analyzed by FLAC3D. Then, an excavation methods conversion opportunity is derived. Meanwhile, the rationality of the opportunity is validated by the field monitoring data. The results indicate that: when the distance of working face cutting through the interface is 1.5B (B = tunnel width), displacement direction angle of surrounding rock reaches a stable state and the longitudinal stress concentration is weakened. It is conducive to utilize the self-bearing capacity of the rock mass. Hence, it is suggested to convert the excavation methods when the distance is greater than 1.5B; the stable value and the convergence rate of vault subsidence in site were both below warning value, which can meet the safety and economic benefits of engineering.
KeywordsShallow-buried tunnel Displacement direction angle Upper-soft and lower-hard Excavation methods conversion
The authors appreciate the support of Science and Technology Plan Projects of Hunan Province, China (2010GK3173) and co-sponsored by the China Railway Tunnel Group Science and Technology Innovation Project (2013–30).
- 1.Lunardi, P.: The Design and Construction of Tunnels Using the Approach Based on the Analysis of Controlled Deformation in Rocks and Soils. T&T International ADECO-RS Approach (May 2000)Google Scholar
- 2.Zhao, C.: Research on key technology of shallow-buried tunnel’s construction method conversion in upper-soft lower-hard strata. J. Railw. Sci. Eng. 6, 1444–1451 (2015)Google Scholar
- 4.Diao, Z., Li, C.: Study on construction method of large-section tunnels in upper soft and lower hard layers. Tunn. Constr. S2, 433–436 (2007)Google Scholar
- 5.Zhang, J., Guo, F., Lei, G.: Study on construction methods of shallow-buried tunnel under condition of upper-soft lower-hard ground by numerical simulation. Chin. J. Undergr. Space Eng. S1(7), 1416–1421 (2011)Google Scholar
- 6.Liu, T., Zhao, S., Sun, F.: Security analysis of dismantling temporary supports of large-span shallow tunnel in upper-soft and lower-hard stratum. Rock Soil Mech. S1, 306–310 (2014)Google Scholar
- 7.Wang, Z., Qiao, C., Song, C.: Calculation method of relaxation pressure of shallow large span tunnel in up-soft/low-hard rock stratum. Rock Mech. 35(8), 2342–2352 (2014)Google Scholar
- 8.Schubert, W., Budil, A.: The importance of longitudinal deformation in tunnel excavation (1995)Google Scholar
- 9.Zhang, Y., Wu, X., He, C.: Study on application of displacement vector orientation trend line to wushaoling tunnel. Chin. J. Rock Mech. Eng. 26(7), 1448–1456 (2007)Google Scholar