Investigating the correlations between point load strength index, uniaxial compressive strength and Brazilian tensile strength of sandstones. A case study of QwaQwa sandstone deposit

Abstract

Investigating the correlations between mechanical properties of rocks and rock masses is important in the design of underground openings and deep foundations in civil engineering. Mechanical properties serve as input parameters for evaluating the stability analysis and to understand the realistic behaviours of the rock. Sandstone specimens were subjected to point load index test, uniaxial compressive strength test, and the indirect tensile strength test. A set of five specimens were used for each test. The results of the laboratory tests were statistically analysed and these showed that point load index test results had strong correlation coefficient with the UCS test results. However, the point load diametral results indicated a very weak correlation coefficient with the Brazilian tensile strength test results. An inconsistency in the results between the UCS and the indirect tensile strength was observed and this can be attributed to the heterogeneity of the sandstone specimens which influenced the failure mode and strength of the rock.