Enyue Ji

By Zhongzhi Fu, Shengshui Chen and Enyue Ji

Rockfill dams are very widely constructed all over the world due to their good adaptability to diverse geological and geographical conditions, and their relatively low cost compared to other dam types. However, natural satisfactory sites are increasingly difficult to find in many countries due to past dam development. In some circumstance, building dams over thick overburden layers is unavoidable. In this chapter, Chinese practices in constructing high earth and rockfill dams over thick overburden layers are reviewed. The geological and geotechnical investigation techniques are briefly summarized, and seepage control systems of some selected cases as well as the connection of the impervious systems of both the dams and their foundation layers are described. Commonly used foundation improvement techniques are also presented, followed by simple descriptions of aspects that require further research and development.

Part of the book: Dam Engineering

By Yijiang Zhang, Enyue Ji and Weiwei Xu

Slope instability is one of the most common forms of dam failure. The commonly used slope stability analysis methods ignore the uncertainty and randomness of dam materials, which may overestimate the stability of dams. In this chapter, a deterministic slope stability analysis based on strength reduction finite-element method is introduced first. After that, the slope is investigated using simple probabilistic concepts and classical slope stability techniques, and the shear strength is treated as a single random variable. Further, the random finite-element method (RFEM) is shown, in which spatial correlation and local averaging are illustrated in detail. Finally, the RFEM is applied to slope stability risk assessment, and the results can lead to higher probabilities of failure.

Part of the book: Dam Engineering

By Zhongzhi Fu, Shengshui Chen, Enyue Ji, Guoying Li and Yang Lu

Constructing the impervious system of an Earth Core Rockfill Dam (ECRD) usually needs a large volume of clay that may exhaust a huge area of farmland. One way to reduce the volume of clay to be filled is to use natural clay-gravel mixtures (CGM) or to add an appropriate percent of gravel materials into the clay and use the artificial clay-gravel mixtures as the impervious core materials. Using clay-gravel mixtures can also effectively increase the modulus of the core and reduce the differential settlement between the core and its adjacent rockfill shoulders, and thus alleviate the risk of occurrence of potential cracks within the core wall. The impermeability behavior of the compacted clay-gravel mixtures, however, has to be careful investigated and verified. In this chapter, four cases in using clay-gravel mixtures in constructing high ECRDs in China are reviewed, with attention focused on the engineering properties of clay-gravel mixtures and the construction and field quality control aspects of ECRDs using clay-gravel mixtures.

Part of the book: Dam Engineering