锦屏层状大理岩断裂机制的细观试验研究

 锦屏地下深埋岩石处于高应力状态，地下洞室开挖后围岩变形破坏所引起的工程问题十分突出。结合取自锦屏二级交通辅助洞的层状盐塘组大理岩及均质的白山组大理岩，利用扫描电镜高温疲劳试验系统，对层状盐塘组大理岩进行不同作用方向下的三点弯曲试验，并和均质的白山组大理岩试件进行对比分析研究层状大理岩不同层理方向的细观断裂机制及其与特征参数间的关系，同时，研究层理与主应力方向的关系对洞室围岩破坏机制的影响。结果表明：围岩层状特性是由于白云石及方解石矿物条带状分布所致；作用力方向对层状围岩的断裂机制有着决定性的影响，均质白山组大理岩试件细观断裂机制为沿晶断裂，作用力方向垂直盐塘组大理岩层理时为穿晶断裂与沿晶断裂的耦合作用模式，作用力方向平行层理时则以沿矿物条带间的沿晶断裂机制为主；断裂机制的不同使得宏观上的强度参数呈规律性差异，盐塘组平行层理试件与白山组试件的峰值荷载分别为盐塘组垂直层理的58%，44%，峰值断裂能分别为42%，29%；作为断裂机制外在宏观表现的3组试件断面形貌具有自相似分形特征。

MESO-EXPERIMENTAL STUDY OF FRACTURE MECHANISM OF BEDDED MARBLE IN JINPING

Because of surrounding rock deformation fracture in deep-buried and high geostress conditions,the project problem is very prominent at Jinping II hydropower station underground engineering.The bedded marble which is collected from the Jinping II hydropower station auxiliary traffic tunnel is used for three-point bending experiment on different loading directions with the scanning electron microscope(SEM) high temperature fatigue testing system.The relation between different bedding directions marble s failure mechanism and strength parameter is analyzed through comparison with homogeneous marble;then the infection to fracture mechanism of surrounding rock by the different loading directions to bedded marble is researched.The results show that the banded structure feature between dolomite mineral particles and calcite mineral particles leads to bedded features of marble;loading direction is the final factor to the fracture mechanism,the failure mechanism of homogeneous marble is that the crack propagation propagate between dolomite mineral particles,when loading direction plumb the bedding;the failure mechanism is coupling fracture with that the cracks penetrate calcite mineral particles and propagate between dolomite mineral particles;and when loading direction parallels to the bedding,the failure mechanism mainly is that the cracks propagate between mineral particles.The difference of strength parameter is disciplinary on macroscopy because of different fracture mechanisms,such as the peak load of homogeneous marble and parallel bedding specimen is 0.58 times and 0.44 times than vertical bedding specimen s;and the breaking energy is 0.42 times and 0.29 times.The three groups of marble fracture surface as the fracture mechanism expression on macroscopy has self-similar fractal features.