Based on the hierarchical block element method presented earlier

a new concept of subordinate cover and a method to simulate the tension crack in rocky block are proposed. In the new method

each block and its covering element are conceptually divided into many cells that are called as the subordinate covers. The smeared crack model is introduced to the cracked cell and the cracking is regarded as a viscoplastic flow procedure. The out-of-balanced or residual forces arisen in cracking are transferred and the structures will get to equilibrium through the iteration. Thus

both the structural discontinuities and the tension crack propagation of rocky block can be effectively taken into account. Numerical examples show that the proposed method can give reasonable results.