Abstract: The demarcation of homogeneous structural domains within rock mass is normally the first step of rock engineering design, since mechanical and structural properties vary largely from one homogeneous domain to another. Most of researches focus on occurrence or the other joint parameters to statistically identify homogeneous regions or structural domains in jointed rock mass. However, only few studies have been conducted by integrating both of them. In this study, by considering the factors of joint occurrence and trace length, a novel method is developed for dividing the statistical homogeneous area of jointed rock mass, which is known as the Wilcoxon rank sum test. It is used to evaluate the degree of the similarity between two samples and then to realize the division of this region. Based on the data of occurrence and trace length of rock mass from four adits at two levels of the left abutment of Maji hydropower station in Yunnan province, the proposed method is applied to statistically identify different homogeneous domains, and to analyze the influence of multi parameters of jointed rock mass on a statistical homogeneous division. The results indicate that, the rock masses within the adits of PD241 and PD253, PD201 and PD241 are incorporated into a statistical homogeneous area, respectively, but those of PD201 and PD251, PD251 and PD253 are situated at different structural domains. Compared to Miller method, the results obtained by the proposed method are more likely to be reasonable and reliable. In comparison with field investigation, it is found that the results from the new method are more agreement with the actual situation.

Key words: statistical homogeneity, occurrence, trace length, Wilcoxon rank sum test, jointed rock mass