At the Oued Meurad dam, in Algeria, 95 ft. high, constructed about 23
years ago, the earthwork layers were deposited normal to the outer slope,
and as the bank was carried up the water was admitted and allowed to rise
to near the temporary crest, and as soon as the bank had settled, the
earthwork continued another grade, and the same process repeated.
It was the practice until comparatively recently to make the discharge
outlet by laying pipes in a trench under the dam, generally at the lowest
point in the valley, or constructing a culvert in the same position and
carrying the pipes through this, and in the earlier works the valves or
sluices regulating the outflow were placed at the tail of the down stream
bank, the pipes under the bank being consequently at all times subject to
the pressure of the full head of the water in the reservoir. An instance
of the first mentioned method is afforded by the Dale Dyke reservoir,
Fig. 2, where two lines of pipes of 18 in. diameter were laid in a trench
excavated in the rock and resting upon a bed of puddle 12 in. in
thickness, and surrounded by puddle; the pipes were of cast iron, of the
spigot and faucet type, probably yarned and leaded at the joints as
usual, and the sluice valves were situated at the outer end of the pipes.
As the failure of this embankment was, as we all know, productive of such
terrible consequences, it may be of interest to enter a little more fully
into the details of its construction.
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