Abstract: The generations of blocks and discontinuities network model of rock mass are the basis of various mechanical analyses and field analyses. The cutting process of complex blocks is analyzed, the corresponding algorithms are described, and a C++-based program is developed. The concept of oriented shell is added to the data structure of block in order to describe the multiply-connected characteristics of block. The discontinuities can be simple convex polygon and complex concave polygon. General blocks are cut by finite discontinuities, through calculating the intersecting lines of faces, generating loop vectors by searching intersecting lines, generating face vectors by analyzing the relationship of loop vectors, generating shell vectors by topologically searching face vectors, generating blocks by analyzing the relationship of shell vectors and so on, and then a general method of block cutting is proposed. The validity check of obtained loop vector, face vector, shell vector and blocks is conducted during the cutting process. The final blocks and discontinuities network model are obtained when satisfying with topological validity check. Four examples are selected to validate the method. The results show that the method can effectively cut complex blocks and the discontinuities can be complex polygon including concave surface, and indicate that the method is universal.

Key words: finite discontinuities, block cutting, complex block, discontinuities network model