Jacob H. Douma
Cavitation Erosion
Well, it sounds from the discussions of
and other projects that a lot of the
problems that arise in these cavitation erosion areas arise from less than adequate
construction techniques. That means the construction is not the way it's designed. How
much did you get involved in that kind of thing with the Corps?
While a job was under construction, I very frequently went to see how things were coming
along. I remember when I was on the consulting board for Magat Dam in the Philippines.
The last time I was there to inspect, it was under construction. The spillway had a
concrete ogee section, followed by a long concrete chute, about 1,500 feet long and 300
feet wide, on a 1 on 10 slope.
I walked over the spillway with the man who was in charge of construction inspection
there. Construction of monolith joints was not done very well. I showed the inspector
one joint that was a half inch higher on the upstream end of the monolith than it was on
the downstream end of the monolith just upstream.
I explained the whole thing about cavitation erosion at monolith joints that I just explained
to you. I said to the inspector, "Normally, this wouldn't be called good construction, but
this dam isn't high enough and the velocity isn't high enough, to cause serious cavitation
erosion. Also, the spillway will operate about once in 5 years, so there will be plenty of
time to repair any cavitation erosion between floods.
But it was an important requirement for you to get out and look at these construction
projects?
That's right.
Also, from what you say, it's only the areas where you had a lot of high-velocity discharge
that you had the problems.
That's right. When the velocity was under about 50 feet-per-second, or there was not a
lot of discharge with velocities over 50 feet-per-second, cavitation erosion was not a big
problem. I told the districts that anytime large flows occur, they should check to see if
there's any cavitation erosion.
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