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One of the core issues affecting the safety of high concrete faced rock-fill dams (CFRDs) is the extrusion damage of the concrete face slabs. In this paper, the causes of the face-slab extrusion damage under long-term operational conditions are studied. It is found that not only the creep behavior of the dam materials but also the circulating water load in the reservoir is responsible for the uneven deformation of the dam that induces the extrusion damage of the face slabs. The possibility of the potential extrusion damage of the face slab of the Dashixia dam, which is now under construction in Xinjiang, China, is further predicted by means of a three-dimensional finite element analysis (FEA). In the FEA, a unified generalized plasticity model that can reflect the volumetric contraction property during the unloading phase of coarse-grained materials is adopted to overcome the shortcomings of previous studies where the effects of the circulating water load are neglected because of model limitations. Then, combined with an incremental creep model, the long-term operational characteristics of the Dashixia dam are predicted and thoroughly discussed. Moreover, a submodel of the face slab is developed and introduced in the analysis to simulate the compressive stress along the thickness of the face slab. According to the results, it can be concluded that extrusion damage of the face slab of the Dashixia dam may occur under the current design conditions, and it is recommended to take some engineering measures to strengthen the slab. K E Y W O R D S face-slab extrusion damage, high concrete faced rock-fill dam, long-term characteristics 1 INTRODUCTION Recently, concrete-faced rock-fill dams (CFRDs) have rapidly developed worldwide because of their good economic efficiency. Historically, most CFRDs have been designed according to similar engineering experience, 1,2 and there have been some cases of extrusion damage of the face slabs, such as that of the Barra Grande dam and Campos Novos dam (in Brazil), and Tianshengqiao-I and Shuibuya (in China), as seen in Figure 1. It is worth noting that the extrusion damage always occurred within a narrow width range between the slabs near the riverbed, along the compression joint, and in the top area of the slabs. Previous researchers investigated this phenomenon and revealed that the uneven deformation of the rock fill under long-term conditions is the fundamental reason for the extrusion damage of riverbed slabs. 3-5 Khosravi et al. 6 used a 668

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