I am designing my
first water-retaining structure - a series of 3 underground rectangular tamks,
each 20m x 20m x 2.5m deep with 355mm (14") wall thickness. We have 60 degrees
Celsius range of temperature here in Quebec.
The total length is
thus 60m, which is a long way to go without joints. But I would like to
avoid joints like the plague, so I have elected to use a separate structure for
each tank. So I have a double-wall between the tanks, with
the intention to pour the walls of one tank, apply a bond-breaker on the
face of the common wall, and then pour the second tank, and so
I don't like it,
because it complicates the wall ties for the second wall of the double-wall
section. And then I have to cover the joint with flashing to keep out the
water in our freeze-thaw climate. But the experts in my books seem to
agree that no joint is a good joint,... well maybe construction joints are a
necessary evil and can be done well.
What do you
think? Is it better to separate the tanks as I have proposed, or to
simplify the construction and add a joint or two ?
What do you do with
the wall ties ? Do you use conical ends, and patch the holes? Will
non-shrink grout do the trick?
about pouring the wall in alternate sections, leaving short sections to
infill after a week or two? Is it worth it?
I have been
researching this and doing my calcs for 3 days now, and I have
accumulated a lot of notes from my references, but they can't answer
everything I guess...
I have heard horror
stories of engineers in court because of leaky tanks, so I am very wary.
One reference I use is in a chapter on water-retaining structures by B.P. Hughes
at the University of Birmingham. He mentions the importance of
limiting crack widths to 0.1mm (0.004"), which usually controls the
design. And so it does in this case. Steel stresses are way down at
about 50 MPa (7,000 psi). Interesting. It's very different from