Using the Core Strangle Test for Determining Uniaxial Compressive Strength of Intact Rock by an Indirect Method

Uniaxial Compressive Strength (UCS) of rock material is one of the most important and effective parameters in geotechnical and mining projects. Direct evaluation of UCS is expensive and time-consuming, therefore indirect tests such as point load, Schmidt hammer and sound wave velocity tests have been developed, among which the point load test is very commonly used, simple and economic. However, this method has limitations such as the effect of loading direction, the application of load to a small part of the rock and the high dependency of the results on the dimensions of the sample. In 2009, the Core Strangle Test (CST) was developed, which has the advantage of applying load through a circle perpendicular to the core axis. In this paper, the results of designing and manufacturing a CST machine, which has been performed for the first time in Iran, are described in order to estimate the UCS of rocks with high accuracy and low cost. The design and construction of the machine were done in the rock mechanics laboratory of Yazd University. In order to calibrate the machine, 70 standard rock and concrete samples with lengths of 20, 10 and 5 cm and a diameter of 54 mm were prepared. In addition to CST, point load and direct UCS tests were performed on these 70 specimens. Then, the relationship between UCS obtained by direct, CST and point load methods was investigated. Calculations showed that the relationship between UCS and machine oil pressure at the moment of failure in the CST method is a linear relationship with a correlation coefficient of 0.78 and the relationship between UCS and point load index is also linear with a correlation coefficient of 0.63.