Parametric Study of Concrete-Face Performance in Cfrds Considering Hardening Behavior of Rockfill Material

Concrete-faced rockll dams (CFRDs) have been widely used for multi-purposes over the world. The construction of CFRD involves placing the rockll in nite thickness layers as a dam body material, and compacting them to reach desired height. A reinforced concrete slab is then constructed at the upstream face of the dam. The concrete face will transfer the water pressure imposed by reservoir to the rockll and nally to the dam foundation. During impounding of CFRDs reservoir, the upstream concrete face undergoes deformations, resulting in the development of compressive and tensile stresses in the impermeable face. Where, generated stresses exceed allowable values, some cracks would develop in the face and cause deciencies in the performance of CFRD as a water barrier structure. Regarding the fact that the dam body deformation as a result of reservoir imposed pressure, has a direct eect on concrete face deformation, adopting a suitable constitutive model to simulate rockll material behaviour, is of particular concern in predicting deformation and developed stresses in the concrete-face of CFRDs. With regard to the previous works on the behavior of rockll material using large scale test equipments, the behavior of rockll is found to be non-linear, inelastic and pressure dependent which claries the signicance of adoption of a convenient model as dam body material. In this paper, to evaluate the capability of dierent models to predict the deformation of dam body material and subsequence eect on upstream face, two elasto-plastic constitutive models have been selected and calibrated using triaxial test results. After selection of more proper model based on comparison by measured data in Da'ao dam, the performance assessment of concrete-face in terms of maximum deformation and developed in-slope direction strains, under dierent conditions was continued. Two-dimensional analyses wereconducted employing Finite Element Analysis (FEA) software, ABAQUS. This software has the ability of simulating multi-step analysis as applied for modeling of dam body in multi layers, placing the concrete face and applying water pressure of reservoir during impoundment, in this study. The analyses results, revealed the importance of rockll material behavior in the performance of concrete-face, in addition to the remarkable role of dam height and the friction properties of face-rockll interface.