单轴压缩强度是岩石工程建设中广泛使用的力学参数,直接确定单轴压缩强度相对耗时且较为麻烦。点荷载试验可以间接估算岩石的单轴压缩强度(UCS),试验方式简洁。通过收集到的岩浆岩点荷载试验成果,分析结果表明,(1)大部分转换公式在点荷载强度指数较大时得到偏高的单轴压缩强度值,特别是对部分幂函数;(2)ISRM(American Society for Testing and Materials)建议的取值范围仍然高估了岩石的单轴压缩强度值。为更准确地估算岩石的单轴压缩强度,建议采用点荷载强度指数50sI的二次函数(见式(1))估算岩石的单轴压缩强度,适用范围为0.0 MPa<50sI<15.0 MPa。
The shear behavior of rock joints is important in solving practical problems of rock mechanics. Three group rock joints with different morphologies are made by cement mortar material and a series of CNL(constant normal loading) shear tests are performed. The influences of the applied normal stress and joint morphology to its shear strength are analyzed. According to the experimental results, the peak dilatancy angle of rock joint decreases with increasing normal stress, but increases with increasing roughness. The shear strength increases with the increasing normal stress and the roughness of rock joint. It is observed that the modes of failure of asperities are tensile, pure shear, or a combination of both. It is suggested that the three-dimensional roughness parameters and the tensile strength are the appropriate parameter for describing the shear strength criterion. A new peak shear criterion is proposed which can be used to predict peak shear strength of rock joints. All the used parameters can be easily obtained by performing tests.
