Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

Re: surcharging a site

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Regarding the questions:

1   Most likely the fatty clays will swell if they are within the uppermost 3
ft of the soil mass.

2   Definitely strip the organics, they will interfere with surcharging.

3   Not recommended to install any foundations until surcharging is complete,
the downdrag cannot be accurately estimated.  Clean consistent soil mass is
preferred to calculate friction and lateral stability in the soil mass.

4   Risk is higher than I would accept (IMHO) for spread footings.
Differential movement may be more than tolerable to structure and possibly for
building components that may be carrying additional loads due to uses inside.

I recommend your Geotechnical Engineer reassess methods for increasing site
soils stability.  There are other methods available such as friction piers for
all concentrated loads and soil admixtures tilled in for slab stability.  I
would also recommend additional lab testing (if not already done) for shrink
swell such as UBC standard 18-2, results will give an indication of expected
dimensions for shrink and swell.  Exudation pressure test is another valuable
lab test and will provide indication of upward lift pressures from soil.  With
more information on how the soils are expected to perform you can make more
rational decisions.  My experience with expansive clay has been an expensive
learning ordeal, caution and sophisticated information are the best way to
arrive at reasonable designs.

Good luck,
James D. Fruit, AIA