Abstract: Probability distribution of rock strength parameters is the foundation of reliability analysis and design in rock engineering. Based on the linear yielding criterion (Mohr-Coulomb and Drucker-Prager), the probability density functions (PDF) of friction angle and cohesion are obtained through the theory of distribution for function of the random variable, on the condition that intact rock compression strength follows normal distribution. The PDFs of and show: the probability distributions of rock compression strength and , are not consistent, as do the probability distribution of and calculated under different yield criteria. Then, based on the characters of and ’s PDFs under different variation coefficients and correlation coefficients of yield criteria’s coefficients, the general forms of and ’s probability distributions are analyzed according to the skewness and kurtosis. The coordination problem between the distribution of rock compression strength and shear strength parameters is solved in theory. Finally, the correctness of PDF’s theoretical deduction and the analytical rationality of the method to determine probability distribution form for and are verified by large sample statistics and analysis for and which are obtained from the lots of marble conventional triaxial compression tests. It is believed that the research can provide a theoretical guidance to choose reasonable probability distributions of rock shear strength parameters in probability analysis of rock strength.

Key words: Mohr-Coulomb criterion, Drucker-Prager criterion, intact rock strength, shear strength parameter, probability distribution