Strain threshold of dynamic model for soils based on generalized thermodynamics

Abstract

Based on the fundamental law of thermodynamics the energy dissipation function expression of Hardin-Drnevich model for soil is established. The formula is used to combine with experimental result to discuss the energy dissipation mechanism of different materials for rockfill dam. It is found that the dynamic characteristics of materials of rockfill dam have two thresholds of strain which may define as the first threshold and the second threshold. The study result shows that the ratios of secant modulus to maximum dynamic shear modulus for these two strain thresholds are higher than 0.97 and 0.5-0.8 respectively. From the view point of engineering practice, if dynamic strain of soil is smaller than the first strain threshold, the maximum dynamic shear modulus and constant damping ratio can be used to analyze the dynamic characteristics of soils. The second strain threshold is equivalent to that defined by increase of traditional pore pressure and volume change.