Abstract: It is difficult to search the dangerous block combination and acquire the safety factor precisely because of the numerous planes of weakness, the complicated block system and the diverse slip modes in rock slopes. Based on block element method, the search of dangerous block combination and the calculation of stability safety factor are conducted. At first, a new method for searching dangerous block combination is proposed, according to the results of block element method through strength reduction calculation. Then, the method for computing safety factors is studied; and the double line intersection method is suggested to calculate the safety factor when the abrupt theory of displacement is adopted. At last, several typical examples are calculated with the proposed methods; and the results are compared with those obtained by using the rigid body limit equilibrium method. The results show that it is more accurate by adopting the block element method, because the force and bending moment equilibrium and the nonuniform distribution of stress on the planes of weakness are considered. The proposed method is expected to be widely used to solve stability problems in complicated rock slopes.

Key words: block element method, rigid body limit equilibrium method, safety factor, block combination