Abstract: As a typical oblique inclined bedding carbon slope, Jiweishan slope does not collapse laterally and results in a deposit landslide, but creeps down the dip at initial stage and then turns into an overwhelming apparent-dip rockslide. On the basis of field investigation, several causes of Jiweishan landslide are discussed in terms of lithology, structure, karstification and underground water, weak intercalation. According to failure mechanism, three dimensional stability of limited equilibrium analysis has been done based on key block theory. 3DEC software is brought in to study the apparent dip-sliding mechanism and deformation character by simulating the initial failure process. Parameters value of discontinuous and corroded rock mass for numerical analysis are also discussed. Conclusions could be drawn via analysis that the slope creeps down the dip initially under gravity and tension crack and lateral crack are generated along karstification steep-crossing joints forming independent driving blocks in the rear. Underground water continuously softens weak intercalation and that leads to rising of residual sliding force of driving blocks and stress accumulation in the key block. Finally, the intensive karstification zone is sheared, and it causes overwhelming apparent-dip rockslide. Numerical simulation results demonstrate that after shear strength reduction of weak layer the karstifiction zone is sheared and sliding masses enter into large-scale deformation stage. This shows controlling and hindering effect of the key block and the key factor of Jiweishan landslide’s occurrence is weak intercalation softening. It also indicates that mining goaf mostly leads to increment of compression stress in rock mass over the roof and does not affect displacement of sliding mass.

Key words: apparent dip slide, karstification zone, anti-slide effect of key block, discrete element method