中文摘要：

以锦屏II级水电站深埋试验洞内长度大于1500m的钻孔岩芯为研究对象，统计饼化岩芯断口的宏观破坏特征、饼化数量和厚度，结合声波和数字钻孔摄像测试结果，分析岩体埋深、岩体结构、洞径尺寸、钻孔直径和钻孔方位对岩芯饼化的影响，得到岩芯饼化的空间分布规律；并通过断El电镜扫描试验，得到岩芯饼化的微观断裂机制。分析结果表明：（1）饼化数量与厚度分布符合乘幂函数形式，饼化程度随埋深和洞径尺寸的增大而增大，3倍洞径内岩芯饼化数量最多；（2）饼化岩芯凹凸面的形成与应力分布、内部损伤和矿物结构类型有关；（3）岩芯饼化是地质作用和外界扰动共同作用下发生的，原生微缺陷、结构面和开挖损伤是岩芯饼化起裂的基础，开挖后地应力调整和取芯局部应力解除是岩芯断裂的动力，而持续钻进是促使岩芯周期性断裂成饼的根本原因；钻孔径向压剪、岩芯侧向膨胀和轴向拉伸是岩芯饼化断裂的力学响应；（4）岩芯饼化分区性特征是围岩损伤弱化分区、岩体结构和应力场分布叠加的综合反映。

英文摘要：

According to borehole cores with the length more than 1 500 m in deep tunnels at Jinping II hydropower station, the information of the macro-damaged characteristics, quantity and thickness distribution of discing core were collected and the spatial distribution of core discing was analyzed. Then, the influences of different buried depths, geologic structure, tunnel geometric size, drilling diameter and directions on core discing were studied in combination with the results of elastic wave test and digital borehole images. Simultaneously, by applying scanning electron microscope technique for discs＇ surface, the micro-damage mechanism was discussed. The results indicated that： （1） The relationship between the quantity and thickness distribution was similar to a power function form. The quantity of core discing increased with depth and tunnel dimension. Within the zone of 3 times of tunnel diameter, core discing occurred more frequently. （2） The convex-concave formation was related to stress distribution, internal damage and mineral structure types. （3） Core discing often occurred under the joint action of geological and external effects. The native micro defects, structural plane and external disturbance werethe discing foundation; the local stress concentration and stress release were the power of discing; the continuous drilling was the intrinsic cause of core broken into pies; the radial cut-compressive, axial tensile stress and lateral expansion of rock cores were the mechanical response of rock mass fracture. （4） Discing zone characteristics were the comprehensive reflection of rock damage weakening, rock mass structure and local stress concentration.