Assessing In-situ Nonlinear Model Parameters for Material of Changheba High Earth Core Rockfill Dam Through Finite Element Analysis

The in-situ material engineering parameters of Changheba dam, the highest ECRD built on thick overburden in China, is studied through FE analysis. The nonlinear model proposed by Duncan is selected to simulate the stress-strain relationship of soil and rockfill materials. The dependence of the permeability coefficient of clayey material on the void ratio is considered. FE analysis based on laboratory tested parameters is performed. Meanwhile, parameters back analysis is conducted based on monitored deformation and pore pressure at the end of construction. The analyzed results show that the in-situ parameters of some dam material are quite different from in-lab tested parameters. The in-situ modulus and friction angle of blast rockfill material is smaller than in-lab tested values. The difference might be caused by scaling effect of particle size and depends on scaling ratio between in-lab samples and in-situ material. The overburden might have a higher in-situ modulus than laboratory tested samples, which might due to the in-situ long-term stress history and scaling effect. Both high pore pressure and small settlement is observed in the core wall. It is shown by back analysis results that the gravelly clay core may have lower in-situ permeability and relatively higher stiffness. The stress path in in-situ gravelly clay core is different from which in in-lab triaxial test might be an important cause.