1.Coal Mining Branch,China Coal Research Institute,Beijing ,China;2.Coal Mining and Designing Department,Tiandi Science&Technology Co.,Ltd.,Beijing ,China;3.State Key Laboratory of Coal Mining and Clean Utilization,Beijing ,China

It is difficult to obtain the standard coal samples for the fragile coal samples, and the uniaxial compressive strength cannot be measured directly.The point load meter is used to test the laboratory point load strength of the broken coal in the form of cylinder and irregularity, and the 30 sets of test data are analyzed by mathematical statistics method. The distribution law of coal block point load strength index and its relationship with equivalent diameter were obtained. At the same time, combined with the previous uniaxial compressive strength and point load strength index formulas and its applicable scope, the uniaxial compression strength of fragile coal body in Xinyuan Coal Mine was obtained. The results show that the coal load intensity index follows the Weibull Distribution,and there is no significant difference in the shape distribution with the block size.For the point load test data clustering analysis, the point load intensity index is inversely proportional to the equivalent diameter.By establishing the relationship between uniaxial compressive strength and point load strength index, it is concluded that the uniaxial compressive strength of the coal body in the broken area of Xinyuan Coal Mine is 0.7～4.9 MPa. It is of great significance to study the load strength test of fragile coal body and quantitatively estimate its uniaxial compressive strength, which provides a basis for surrounding rock support of broken coal roadway.