Environmental Engineering Reference
In-Depth Information
Figure 13.12.
Piping failure of a dam around the outlet conduit.
- The conduit is joined to a “stiff” structure, e.g. outlet shaft or concrete core wall;
- Poor detailing of joints in design or construction;
-Water flows in the conduit under pressure fluctuate giving a surging effect;
- The conduit is old and corroded.
(b)
Continuation and progression
- the conduit facilitates continuation and progression by:
- Maintaining an open joint;
- Carrying away the soil which erodes into the conduit - so the seepage pressures do
not have to erode the soil any great distance through the dam. However the pro-
gression of piping may be limited or slowed due to the limited width of the open
joint or crack.
(c)
Breach
- the conduit does not in itself form a breach mechanism. Those failures which
have involved erosion into the conduit have also involved erosion along the conduit.
It is possible (probable?) that the initiation of erosion along the pipe was aided by erosion
into the pipe. A breach mechanism can occur if the erosion progresses to form a large
sinkhole which collapses at the crest leading to loss of freeboard.
