Small strain characteristics and threshold strain of dynamic Hardin-Drnevich model for soils

Based on the hyperbolic skeleton curve of Hardin-Drnevich,small strain dynamic dissipation function was formulated by adopting the Masing rule.Then the corresponding yield surface and energy dissipation characteristics were analyzed.It was indicated that there existed two threshold strains which were defined as the first threshold strain and the second threshold strain respectively for dynamic characteristics of non-cohesive rockfill material.The two threshold strains divided the soil dynamic characteristics into three sections.When the dynamic strain is below the first threshold strain,the yield of soil was controlled by friction dissipation of the constant friction coefficient.When the dynamic strain was between the two threshold strains,the yield of soil was controlled by that of the variable friction coefficient.However,when the dynamic strain was bigger than the second threshold strain,the dilatancy-related structural variation was shown.The two threshold strains decreased when the maximum dynamic shear modulus coefficient and exponent increased.In addition,the friction angle of cohesionless soil would also influence them to some extent.