Abstract: Classifying the orientations of rock discontinuities is a fundamental but critically important routine of engineering geology and hydrogeology. The commonly-used rose diagrams of dip directions and strikes and poles to orientations are subjective. It is appreciated to resort to mathematical approaches. In this paper, an automatic grouping method is proposed based on the algorithms of K-means cluster analysis and cluster validity index I, and a Rock Discontinuities Auto-classification Program (RDAP) is developed. By comparing with Shanley and Mahtab’s result (1976), the reliability of the new grouping method or RDAP is verified. In the end, RDAP is used to cluster the gushing fractures to aid in the selection of the optimum position of grouting drillings of a project, which provides a basis for the prevention and control of water gushing.

Key words: rock discontinuities, automatic classification, K-means cluster analysis, cluster validity index I, RDAP, grouting drillings, optimum position