1998 – Repair of Two Dams Suffering Leakage – Two Case Studies

Nikifor Petrovic

One of the most important issues during design and construction of an earthfill dam is how to secure a dam against unwanted events which may occur as a result of water flow (uncontrolled seepage, leakage & piping) through the dam.

Although earthfill dams are the largest by volume compared with other types of dams and they are designed to cope with seepage, their integrity is most sensitive to the effects which may be caused by it. The reason being that the earthfill materials are generally extremely heterogeneous and only one “unwanted” pocket is enough to create problems.

Another critical area is the foundation. In many situations it is not possible to avoid the complex geology which includes faults and joints as part of the foundation. An additional complication may be the presence of dispersive clay in the foundation.

In the area of tailings dams, the problems with seepage are slightly reduced as in most cases, tailings provide a degree of sealing. Tailings dams are very often designed as leaky dams. However, there is a hidden danger in approaching the design this way as at any stage of their lives they can retain water.

This paper presents two case histories of repairs carried out to tailings dams suffering leakage. One case describes leakage through the embankment wall while the other describes seepage through the foundation which contains dispersive soil.

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