Tensile strength test of coal and rock with different coal structure

Coal and rock, as a special sedimentary rock, mostly undergoes multiple phases of tectonic movements after its formation, resulting in the diversity of coal structures. Therefore, it is difficult to directly use a certain method to test the tensile strength of coal and rock with different coal structures. In order to obtain the tensile strength of coal and rock with different coal structures, taking No.10 of Suntuan Coal Mine of Huaibei Mining (Group) Co., Ltd. as an example, the Brazilian splitting test and the point load test are conducted on coal and rock with different coal structures. The results show the following three points. ① The average tensile strengths of primary structure coal and fractured coal measured by Brazilian splitting test are 1.174 and 0.710 MPa respectively. The average point load strengths of primary structure coal, fractured coal, crushed coal and mylonite coal measured by point load test are 0.368, 0.248, 0.112 and 0.041 MPa respectively. ② The point load strength and tensile strength of coal have a good linear correlation. The point load strength and tensile strength test results are linearly fitted to obtain the conversion equation between the point load strength and the tensile strength. According to the equation, the calculated average tensile strengths of crushed coal and mylonite coal are 0.345 and 0.126 MPa respectively. ③ From primary structure coal to fractured coal, crushed coal and cinder coal, the tensile strength of coal rock decreases significantly with the increase of the damage degree of coal structure, and the decline tends to increase gradually.