Chapters authored
Practices in Constructing High Rockfill Dams on Thick Overburden Layers
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
Using Clay-Gravel Mixtures as the Impervious Core Materials in Rockfill Dams
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