Rock Mechanics and Rock Engineering

, Volume 45, Issue 3, pp 289–309 | Cite as

A Top Pilot Tunnel Preconditioning Method for the Prevention of Extremely Intense Rockbursts in Deep Tunnels Excavated by TBMs

  • Chuanqing Zhang
  • Xiating Feng
  • Hui Zhou
  • Shili Qiu
  • Wenping Wu
Original Paper

Abstract

The headrace tunnels at the Jinping II Hydropower Station cross the Jinping Mountain with a maximum overburden depth of 2,525 m, where 80% of the strata along the tunnels consist of marble. A number of extremely intense rockbursts occurred during the excavation of the auxiliary tunnels and the drainage tunnel. In particular, a tunnel boring machine (TBM) was destroyed by an extremely intense rockburst in a 7.2-m-diameter drainage tunnel. Two of the four subsequent 12.4-m-diameter headrace tunnels will be excavated with larger size TBMs, where a high risk of extremely intense rockbursts exists. Herein, a top pilot tunnel preconditioning method is proposed to minimize this risk, in which a drilling and blasting method is first recommended for the top pilot tunnel excavation and support, and then the TBM excavation of the main tunnel is conducted. In order to evaluate the mechanical effectiveness of this method, numerical simulation analyses using the failure approaching index, energy release rate, and excess shear stress indices are carried out. Its construction feasibility is discussed as well. Moreover, a microseismic monitoring technique is used in the experimental tunnel section for the real-time monitoring of the microseismic activities of the rock mass in TBM excavation and for assessing the effect of the top pilot tunnel excavation in reducing the risk of rockbursts. This method is applied to two tunnel sections prone to extremely intense rockbursts and leads to a reduction in the risk of rockbursts in TBM excavation.

Keywords

TBM Rockburst Top pilot tunnel FAI ERR ESS 

Notes

Acknowledgments

The authors gratefully acknowledge the financial support from the National Science Foundation of China under Grant Nos. 2010CB732006, 51079144, and 50979104, and the National Science Foundation of Hubei Prince in China under Grant No. 2010CDB10404. The work in this paper was also supported by research funding from the Ertan Hydropower Development Company, Ltd., and an important pilot tunnel project (for youth talent) of the knowledge innovation project of the Chinese Academy of Sciences (CAS) (No. KZCX2-EW-QN115). We are also grateful for the support and assistance of the engineers at the East China Investigation and Design Institute with the headrace tunnel design and construction. Special thanks go to Prof. Giovanni Barla and the two anonymous reviewers for their constructive comments.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Chuanqing Zhang
    • 1
  • Xiating Feng
    • 1
  • Hui Zhou
    • 1
  • Shili Qiu
    • 1
  • Wenping Wu
    • 1
  1. 1.State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhanPeople’s Republic of China

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