Abstract:For gravity dam with weak intercalated layer in foundation,the shear strength of the weak intercalated layers is the main factor in the control of the dam stability. It is the key point of geological and experimental work to ensure the shear strength to satisfy safety and economy of dam. The material composition,mineralogical composition and structure,genetic type and characteristics of shear stress and strain of weak intercalated layer in dam foundation of Majiayan reservoir are analyzed,the valuation rule of the shear strength of weak intercalated layer with plastic failure mode is discussed,and finally the recommended geological value of shear strength of weak intercalated layer in this project is proposed.