Does anyone have experience with use of cemented filters?
We have a project with a very-very large canal. In certain
areas it has been determined that there is a requirement for
0.2 to 0.3 m thick sand filter behind the concrete lining. To
complicate matters, the sand must be compacted to 70-80%
relative density. This project is one of the largest
canal/wasteways built in the world. Attempts have been
made to compact the sand with a canal paving machine - but
the density could not be obtained. It would not be very
economical to roller compact on the side slopes.
The sand is a pit run material with 5-7 % fines. Washing is
also a major cost to be avoided.
An option would be to make a slightly cemented filter, with
say 2% cement. This material must have K > 1x10-3
cm/sec. We have shown we can make it. The question is
the long term performance.
The filter will serve to draw down natural groundwater table
and to drain behind the lining for rapid drawdown conditions.
The area is arid and likely to have akaline groundwater
conditions.
Has anyone out there dealt with the long term performance of
cemented filters? Will the material serve it's purpose 30
years down the road? Our guess is, under akaline
conditions, there should not be major attack on the cement
bonds, but we are looking for some proof!
Your input is appreciated.
Jeffrey A Farrar
Bureau of Reclamation
Earth Sciences and Research Laboratory
PO Box 25007 D-8340
Denver CO USA 80225
303-445-2333
fax 445-6341
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