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Abstract The maximum principal stress of Jinping II headrace tunnel is more than 70 MPa. In such a high stress condition，there must be sharp conflict between rock mass strength and geostress. Understanding the fracture characteristics of marble and grasping the damage evolution law of surrounding rock，are important to the optimization design of support and evaluation of the stability of surrounding rock. Depending on the research achievements of brittle rock fracture，the characteristic strengths of marble under different confining pressures are confirmed by inflection points of crack volume strain and marble volumetric strain matching with acoustic emission test. The characteristic strengths are expressed in principal stress space；and the stress envelope is set up，which can be used in field. The stress state in excavation damage zone(EDZ) is analyzed by crack initiation strength envelope and the scopes of different zones of EDZ are calculated. The EDZ evolution of monitoring section by tunnel face driving is described. In order to further analyze the evolution law of EDZ above，the acoustic wave and acoustic emission test are conducted. The relaxation depth by acoustic emission detection is mainly corresponding with failure zone in damage zone. The acoustic emission test can obtain the whole EDZ distribution，which is more helpful to understand the complete EDZ distribution characteristics. The results can provide scientific basis for the optimization design and timing of support.
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Received: 16 April 2012
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2012, Vol. 31 
