Soil consolidation using surcharge method . Any other alternative?

http://cr4.globalspec.com/thread/11379#comment106943

Try using 7-part sand and 3-part silt and have it compacted at every layer of 150mm to achieve the 95% compaction factor. If failed, increased the silt % to a maximum of 50% silt and 50% sand.

The sand piles you mention are dry wells, to allow the water in the peat to migrate out of the ground, with little or no pumping of the peat. Placing of your surcharge has to be monitored for sudden differential settlement indicating fluidization of the peat. As the water is forced out, a reasonably stable and moderately bearing, low porosity base is established.

An alternative would be floating your roadway on 2 to 4 meters of rigid foam in blocks of 2 meters³ . This has been used with some success for about the last 10 to 15 years in the US. I think sand wells would still be a good idea.

Rich

Mebbe constructing an elevated highway would be a better choice; both technically and financially.

It depends on so many other factors...

There may be others but the ones I have used successfully are :

1.The "Menard' theory is a trusted method which consists in dropping a flat steel weight generally up to 20 tonnnes from a height of a crane free-wheeling the drop.Generally this is from a height of at least :12 to 15 meters. A good operator will drop it flat on the ground area to be solidified.This creates a mini earth-quake and is effective provided the soil is the right type (best is soft and fine sandy soils)

2.the second system is a Japanese system wherein a special machine places into the ground a "wick" made of paper. In effect this imitates but is much faster than the "sand- wick" or chimneys . The latter are generally used precisely in conjunction with the situation you suggest i.e. of overloading the area to be consolidated with a constant earth or sand loading. In certain soils even pre-loading will not work unless you complement the overloading action with these "chimneys " whereby the underground water is bought to the surface and is rid- of either by surface drains or by evaporation.

Keep us advised .

Labor Omnia Vincit.

Vertical drainage system is only a temporay solution, for eventually ground water from surrounding regions and storm/rain water shall re-flood the sub-terrain region. Then the roads will have bumpy surfaces, as if constructed over marine clays.

Roller compacted Cement Treated Base (CTB) may be another alternative.

Dear All

I express my heartfelt thanks for your kind contribution of ideas. I will study these proposals prior detail discussion with my consultant.

Thanks again

Dave

If you've ever heard of a place called the "Truttman Sink" you'd know that deflection-per-year does not have to go to zero, ever...

You might also want to explore the idea of excavating at least twice as deep, and wide, as you currently think is the maximum allowable, and then lining said excavation with a relatively high-tensile strength, impervious geo-fabric, and back-filling with dry, fine-grained sand, very carefully compacted, extending the fabric entirely around the embankment cross-section laterally, and placing an appropriate roadway section on top of it all. Essentially, it would be a large pontoon placed length-wise under the roadway centerline. It would be more likely to (float), and provide a longer service life, with less maintenance. It would not be cheap, but it would tend to work better...