锦屏深埋大理岩破裂特征与损伤演化规律

 锦屏二级引水隧洞最大主应力超过70 MPa，在如此高应力条件下，必然存在岩体强度和地应力之间的尖锐矛盾。深入认识大理岩的破裂特征，把握围岩的损伤演化规律，对于支护优化设计和评价围岩稳定性具有重要意义。在已有关于脆性岩石破裂问题研究成果的基础上，借助于裂纹体积应变拐点和大理岩体积应变拐点配合声发射测试，确定不同围压条件下大理岩的特征强度，并将特征强度在主应力空间中进行表达，形成现场可用的强度包线。利用起裂强度曲线分析损伤区的应力状态，并根据计算成果确定不同损伤区分区的范围，描述监测断面随掌子面推进过程中损伤区的演化过程。为进一步分析损伤区的演化规律，在监测断面布置声波和声发射测试，声波检测获得的松弛圈深度主要与损伤区中的破坏区相对应，而声发射测试可以获得完整的损伤区分布特征，更有利于了解围岩的损伤特征，可为支护优化设计和支护时机的选择提供更加科学的依据。

FRACTURE CHARACTERISTICS AND DAMAGE EVOLUTION LAW OF JINPING DEEP MARBLE

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.