Technical Challenges and Design Features of the 247-m DaShiXia Concrete-Faced Sand-Gravel Dam

Abstract

The 247-m DaShiXia (DSX) concrete-faced sand-gravel dam (CFSGD) is currently the highest structure of its type under construction in the world. By reviewing the specific conditions of this dam and common problems that have occurred in other comparable cases, this paper analyzes the technical issues that undermine the safety of the dam. Measures for controlling dam deformation and seepage, improving its aseismic performance, and reinforcing its concrete slabs are explained with the aid of experimental and numerical results and previous experience. The results of the analysis demonstrate that the deformation of the dam under static and dynamic loads is within the range of existing successful cases, thus providing fundamental confidence that the design is feasible. The use of L-shaped drainage within the dam is emphasized because of the vulnerability of sand and gravel material to seepage erosion, uncertainties in the results obtained from laboratory seepage tests, and the need to lower the phreatic surface. Numerical results show that the acceleration response is strong within the upper 4/5 part of the dam, which leads to confined aseismic measures within this particular portion. Reinforcing schemes for concrete-faced slabs and their joints are outlined, and some special design features, including the use of a high toe retaining wall, a stepwise toe plinth, and a deep empty tunnel in this dam, are also explained. The measures adopted are expected to result in acceptable performance of the dam and its impermeable system.