The traditional block theory is just used to analyze the static stability of the block

while not concerned with the dynamic stability analysis. Based on block theory

the located block’s dynamic stability under the action of earthquake is studied by utilizing the concept of accumulated slippage of Newmark method. Several important results are obtained. ① By using accumulated sliding displacement and dynamic safety factor commonly to evaluate dynamic stability of the block. ② A contact area identification and area computation algorithm

considering the adverse influence on the block stability caused by the variation of contact area and can do large displacement analysis during block’s sliding. ③ The shear strength evolution of structural plane is considered during the earthquake. ④ It can be used to do static-dynamic analysis to the complicated convex and concave blocks. At last it is applied to analyze the stability of the left slope of shiplift boat box in Three Gorges Project. The results show that the block slides for a distance in the process of the severe earthquake

but it still keeps stable after the earthquake.