ABSTRACT
ABSTRACT: Tarbela Dam the largest volume rock and earth fill dam faced serious seepage problems through its 220 m deep alluvium foundation immediately after its first filling in 1974. The seepage observed surpassed manifolds the designed values. The reservoir was depleted in emergency due to serious structural failures and large seepage. On emptying the reservoir, a large number of sinkholes were noticed in the upstream impervious blanket responsible for large seepages. This paper describes in detail the seepage control measures incorporated in the original design, the reasons for its inability to perform according to designed criteria, geology of the foundation and abutments, causes for the development of sinkholes in the foundation and body of the dam, the treatment of sinkholes under dry and wet conditions and the method of monitoring of development of sinkholes under water. The paper further describes the success of under water treatment of sinkholes in controlling the undue seepages and enhancing benefits of the dam.
