UNCERTAINTY IN KARKHEH DAM FOUNDATION PERMEABILITY

Karkheh Dam is the largest dam, in terms of reservoir capacity and volume of fill placed, constructed in Iran. Its foundation presents an unusual alternation of highly pervious conglomerate and layers of very low permeability mudstones. The pervious conglomerate is extremely inhomogeneous in nature with different matrix materials and different grade of cementation. At different stages of dam design, construction and impounding comprehensive study was performed to estimate the permeability of the conglomerate, which was a difficult engineering task. Due to complexity of the conglomerate formation, and the nature of procedures used, the estimated permeability values were significantly varied. Thus with data obtained from feasible methods of investigation and testing there remained significant uncertainty, especially in design stage. In this paper the results of these investigations are compared and discussions are made.