›› 2013, Vol. 34 ›› Issue (9): 2690-2698.

• Numerical Analysis • Previous Articles     Next Articles

Cracking characteristics and influential factors of surrounding rocks induced by excavation unloading in deep tunnel

ZHANG Wen-ju1, 2，LU Wen-bo1, 2，YANG Jian-hua1, 2，YAN Peng1, 2，CHEN Ming1, 2   

  1. 1. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China; 2. Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of Ministry of Education, Wuhan University, Wuhan 430072, China
  • Received:2013-04-27 Online:2013-09-11 Published:2013-09-13

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Abstract: Through the theoretical analysis and numerical calculation, cracking of surrounding rocks in deep tunnel induced by excavation unloading is studied. The cracking mechanisms and their characteristics of quasi-static and transient unloading under high in-situ stress are discussed respectively. For a case of deep circular tunnel the effect of this transient process on cracking of surrounding rocks is investigated by adopting an initiation model of crack under biaxial compression, and revised stress intensity factor is taken as cracking criterion. The analysis results show that the stress of unloading is a significant cause of surrounding rock cracking; the tensile stress zone exists under transient unloading; and the tensile stress plays an important role in the surrounding rock cracking under high in-situ stress; the less the duration of excavation unloading is, the larger the tensile zone and cracking range will be. The cracking depth and range increase with increasing lateral pressure coefficient; and the cracking region is approximately in V-shape. This study may be of great significance for further understanding the failure mechanism of surrounding rocks.

Key words: cracking mechanism, transient unloading, fracture criterion, stress intensity factor, surrounding rock

CLC Number: 

  • O 319.56
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