Identification of structural domain boundaries at the Songta dam site based on nonparametric tests

• We propose a method for identifying structural domain boundaries in rock masses.
• The 34-sector network is utilized to process joint orientation data.
• Nonparametric tests are used to evaluate the homogeneity of structural populations.
• The new method provides a quantitative, standard scale to determine domains.

Identification of structural domain boundaries in a rock mass is an essential step for rock engineering design, because mechanical and hydraulic properties vary from one domain to another. A new method in which structural domain boundaries were determined by comparing the number of joint poles occurring in corresponding sectors on stereonets was proposed. The Kolmogorov–Smirnov and Wilcoxon rank sum nonparametric tests were used to evaluate the homogeneity of the structural populations collected from four adjacent adits at the Songta dam site. Based on a significance level of 0.05, the structural domain boundaries in the rock mass of the study area were determined. A major advantage of the new method is that it provides a quantitative, standard scale to evaluate the homogeneity of structural populations without the knowledge about joint sets. It can produce more reliable evaluation results attributed to using different statistical tests. In addition, it is applicable to structural populations with small sample size.