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RE: Water reservoir - joints, wall ties, and alternate pours

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I've done above grade liquid-containing structures in the 150-175-ft range (45-53 meters) without crack control joints but using heavier reinforcement as recommended for liquid-containing structures and providing construction joints at a spacing of about 40-ft (12- meters). Since your structure is buried, that may help to reduce temperature and moisture changes, so you may be able to justify going longer without contraction or expansion joints. Walls have a tendency to crack near the base of wall due to restraint from the slab, so we sometimes increase our reinforcement just above the base slab. If you use a low water-cement ratio and good curing techniques, that will also help.
 
 
 -----Original Message-----
From: Kevin Below [mailto:kevin.below(--nospam--at)sympatico.ca]
Sent: Thursday, March 14, 2002 3:48 PM
To: seaint(--nospam--at)seaint.org
Subject: Water reservoir - joints, wall ties, and alternate pours

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 on.
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?
 
What 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 buildings.
 
Kevin Below
Génécor inc., experts-conseils