Seismic responses of high concrete face rockfill dams:A case study

Seismic responses of the Zipingpu concrete face rockfill dam were analyzed using the finite element method. The dynamic behavior of rockfill materials was modeled with a viscoelastic model and an empirical permanent strain model. The relevant parameters were obtained either by back analysis using the field observations or by reference to parameters of similar rockfill materials. The acceleration responses of the dam,the distribution of earthquake-induced settlement, and the gap propagation under the concrete slabs caused by the settlement of the dam were analyzed and compared with site investigations or relevant studies. The mechanism of failure of horizontal construction joints was also analyzed based on numerical results and site observations. Numerical results show that the input accelerations were considerably amplified near the top of the dam, and the strong shaking resulted in considerable settlement of the rockfill materials, with a maximum value exceeding 90 cm at the crest.As a result of the settlement of rockfill materials, the third-stage concrete slabs were separated from the cushion layer. The rotation of the cantilever slabs about the contacting regions, under the combined action of gravity and seismic inertial forces, led to the failure of the construction joints and tensile cracks appeared above the construction joints. The effectiveness and limitations of the so-called equivalent linear method are also discussed.

Hydrodynamic pressure on concrete face rockfill dams subjected to earthquakes

The hydrodynamic pressure is an important load on concrete face rockfill dams (CFRDs) subjected to earthquakes,the influence of which,however,is not clear as compared with that in concrete dams.In this paper,the coupling effect between the CFRDs and the reservoir water is studied based on two-dimensional finite element simulations by using a verified procedure.It is found that neglecting the solid-fluid coupling effect not only results in an overestimation of the acceleration response within the rockfill materials but also makes an overestimation of the dynamical stresses in the concrete slabs.For a reliable seismic response analysis of the CFRDs,therefore,the hydrodynamic pressure should be taken into account,particularly when the dam is subjected to a simultaneous excitation in both horizontal and vertical directions.Numerical results show,however,that the compressibility of the water can be safely neglected in the seismic response analyses of the CFRDs even when the dam is as high as 300 m,except when the excitation is quite abundant in high frequency contents.