Application of slip line theory and core drilling in the prediction of rock c- parameters

The cohesion c and the internal friction angle phi (hereinafter referred to as the c-phi parameters) are the basic parameters that characterise rock strength. This paper proposes a method that makes use of digital core drilling in the prediction of rock's c-phi parameters. Based on slip line theory, this paper develops a core drilling rock cutting mechanical model and obtains the quantitative relationship between core drilling parameters and the rock c-phi parameters (CDP-c phi relation). Using the rock mass digital drilling test system developed in house, the digital core drilling of rock specimens in a laboratory setting was performed. Based on these experiments, a method that predicts rock c-phi parameters using digital core drilling parameters based on slip line theory was proposed. Additionally, c-phi parameters predictions and laboratory triaxial test values were used to compare and analyse the method. The results indicate that the difference and fluctuation of the theoretical values and the test values are small, and the reliability of CDP-c phi relation is high. The proposed method can obtain rock c-phi parameters at underground project sites accurately.