Research And Application Of A Thermodynamic Constitutive Model Of Granular Materials

Concrete faced rockfill dam is an important dam type in China’s current dam construction. As a major part of the dam, the study of rockfill’s stress and deformation behavior is particularly important. The traditional models of soil as Duncan Zhang, Tsinghua KG nonlinear model and Shen Zhujiang yield surface model are widely used in practical engineering calculations. These models can reflect part of the features of the soil, but they also have some drawbacks, such as too many parameters,unclear physical meanings, no reflection of the stress path, not conformed to the thermodynamics theory.This paper analyzes the change process of the stress ratio of Pankou and Shuibuya CFRD dams during construcion and draws a conclusion that the stress ratio remains nearly constant. And in the framework of thermodynamics, this paper derives a nonlinear elastic model of rockfills under the law of conservation of energy, analyzes the index of the model and verifies the conservative energy in the closed stress paths, uses the fitting parameters to calculate the three axis test and compares the results.This model conforms to the laws of thermodynamics and can reflect nonlinearity, dilatancy and stress induced cross-anisotropy of soils. More importantly, the model has only four independent parameters with clear physical meanings.Using the model to calculate the world’s highest CFRD Shuibuya of 233 m height, this paper does 2D and 3D finite element analysis under completion and water-storage conditions. Compared with other models and the measured data, this model’s results are nearer to the measured data than others thus further validating the reliability of the model.This paper does parameter sensitivity analysis using orthogonal experiment method. By dividing each parameter into five levels, 25 calculation experiments of different combinition of parameters are taken. Analyzing the results of three points of the downstream section, the results show that parameter n located at the index position has the highest sensitivity and the sensitivity order from high to low is n, G, K, M.