SEISMIC PERFORMANCE OF A CONCRETE FACED ROCKFILL DAM USING AN ADVANCED NONLINEAR 3D NUMERICAL ANALYSIS

摘要

A general methodology is presented for advanced nonlinear 3D dynamic finite element analysis of concrete faced rockfill dams and applied to a dam build in a narrow canyon. Initially a detailed simulation of the phased construction and reservoir impoundment is conducted, using the Duncan and Chang (1970) constitutive model. After calculation of the initial stresses and deformations at the end of impoundment, the dynamic analysis is initiated using a nonlinear hysteretic model that is based on the initial dynamic stiffness of the rockfill material. The model produces hysteresis loops that are in agreement with the experimental data regarding the variation of the shear modulus and damping ratio with the amplitude of cyclic shear strain. The methodology is applied here to investigate the effect of (a) rockfill dynamic stiffness and (b) the possible development of seismic settlements on the seismic the response of the dam and the performance of the concrete slab and joints. Results are presented on the development of (a) tensile stresses at various locations within the concrete slab panels (b) joint separations due to movement of the slab panels and (c) high compressive stresses at the slab-to-slab vertical interfaces that may potentially lead to concrete fracture.