Abstract:The weak intercalations have an impedance action on seismic wave propagation in spite of its adverse influence on engineering body. In the past,the adverse influence has been researched more than their properties of the base isolation. However,the research on the base isolation properties of weak intercalations can not only offer us more theoretic foundation for reducing damage and preventing disasters induced by the action of earthquake waves,but also help to explore the dynamic character of rock joints. In fact,the weak intercalations may be approximately regarded as a kind of joints when they become very thin. Based on some theories of plane elastic wave propagation,the transmission model of weak intercalations for P wave fields is established and used to analyze propagation properties varying with incidence angles,depth,impedance ratio of the weak intercalations. Finally,the mechanism of waveform distortion of transmission wave is also discussed.