As one of the most serious hazards in slope engineering,the collapse is hard to be controlled because the fracture failure mechanism of rock slope with excavation is not clearly.In order to treat this problem,based on the structural character of natural rock slope and by the aid of Rock Mechanism,the stress states of crack initiation before and after the excavation were studied firstly.Then according to Fracture Mechanics,the condition of crack initiation under two stress modes of tension-shear and compression-shear was analyzed,respectively.Meanwhile,taking energy method as main way, by studying the mechanism of input-dissipation of deformation strain energy during unloading, the calculation of the crack growth amount was proposed.Furthermore,the propagation direction was also given and the slope failure mechanism was researched clearly.Finally, an example was given to prove the theory.The result showed that the failure of rock slope under excavation is mainly the result of the discontinuous propagation and continuous accumulation of cracks with special direction under different unloading stress environment,which essence is a process of energy input-dissipation and stress adjustment.
