Comparison and combination of Leeb hardness and point load strength for indirect measuring tensile and compressive strength of rocks

Uniaxial compressive strength (UCS) and tensile strength (BTS) of rocks are very important parameters in the practice of mining engineering, tunneling, slope engineering, etc. The method of obtaining the BTS and UCS of rocks by indirect measurement through point load test is very widely used. In order to improve the accuracy and convenience of indirect measurement, this paper obtained point load strength (IS(50)), Leeb hardness value (HL), UCS, and BTS of six different rocks by indoor tests, compared the results of point load test and Leeb hardness test for indirect measurement of UCS and BTS, and analyzed the correlation of each parameter. The test results showed that both HL and IS(50) could establish better relational functions with BTS and UCS, and the relationship between HL and UCS was more significant as a power function; the relationship between HL and BTS was more significant as a linear relationship; there was a significant linear relationship between both IS(50) and BTS and UCS, and in comparison, the fit between IS(50) and BTS was better. In particular, comparing the error magnitude respectively of indirect measurement of BTS and UCS by ISRM method, point load method, Leeb hardness method, rock classification method, and two-parameter method, it was found that the ISRM method calculates UCS with a high relative error of 10 to 50%, and the rock classification method and two-parameter method calculate results with a small relative error of +/- 10%.