Abstract: Experimental studies indicate that the dynamic shear modulus of rockfill is related to confining pressure and stress ratio; therefore, it is necessary to include the influence of confining pressure and stress ratio in the dynamic constitutive model of rockfill materials. This paper briefly introduce the existing dynamic shear modulus calculation formula considering the confining pressure and stress ratio, and proposes an improved dynamic shear modulus calculation formula. Comparing with the experimental results of dynamic characteristics of Houziyan limestone rockfill, rhyolite rockfill, overburden gravel, transition material and cushion material, the model can better fit the combination of different confining pressure and stress ratios. The experimental data of dynamic shear modulus and dynamic shear strain show that the model has good applicability and prediction accuracy. The Hardin-Drnevich hyperbolic constitutive model is used to the finite element analysis of the dynamic response of Houziyan rockfill dams. The dynamic shear modulus is calculated using the conventional formula and the improved formula presented in this paper. The overall dynamic response of the dam is compared. Using the formula for calculating the modified dynamic shear modulus considering the confining pressure and stress ratio, the maximum acceleration response in all directions of the crest will increase; and the increase value will be about 20%-35%.The maximum dynamic displacement decreases by 14% in the river direction and increases by about 10% in both the vertical and horizontal rivers.

Key words: rockfill dam, dynamic response, shear modulus, confining pressure, stress ratio