Mosul and Haditha Dams are built on relatively weak foundations. Both of these foundations suffer from extensive karsts which had demanded intensive foundation treatment works among other design precautions. The karst forms; however, are of different origins, activities, nature and shapes. The foundation treatment in both dams was done mainly by constructing deep grout curtains along with other secondary grouting works. Reducing uplift pressure under the dam and cutting down on seepage losses were the major considerations in these works. An additional important requirement in Mosul Dam was to reduce the permeability of the rock formation in the foundations to such a low limit that it can stop the dissolution of gypsum beds present there. This objective; unfortunately, failed due to the lithological composition of this foundation and the presence of many brecciated gypsum beds, which could not be treated successfully. This had resulted in a comprehensive grouting maintenance program which continuous up to date with the everlasting danger of dam failure. On the other hand, in Haditha dam no such complication occurs as the dam had its foundations mainly in limestone. Proper investigation and good planning and performance of the grouting works in this dam contributed highly to its success. Selecting the deep grout curtain as anti-seepage measure in Mosul Dam was not a very wise decision and constructing a positive cutoff in the form of diaphragm wall could have been the proper choice. Good and deep understanding of all geological data can contribute to the success of a dam design or, otherwise it may lead to unsafe one.
Keywords: Mosul Dam, Haditha Dam, Karst, Sinkholes, Gypsum, Limestone, Grout curtain. Diaphragm
ISSN: 1792-9040 (Print)