Soil Stabilizations for small house project

[sybie99]

Hi

I am the design engineer on a house project. The geotech report found the underlying soil to be unsuitable for bearing the foundations down to 1.7m where a rock layer is found. The QS priced different options we presented to bring the foundations up to ground level. The cheapest would be to stabilize the in situ soil with cement. We will get a lab to test the soils suitability for stabilization. My question is, for such a small project, how is the cement mixed with the the in situ soil in an economic way?

 

[salman85]

hi Sybie99,

After you get the spesification (mix design), you can do this thing :
- Spread the select granular fill (as per spesification) upto 250mm thickness
- spread the cement
- mixed with shovel/trowel/hoe
- add water as per specification (eg 4% depend on spesification)
- compaction with hand stamper/baby roller

Do this sequence upto design level...remember, reaction between water and cement could be 4 hours..

 

[moe333]

For a 1.7m depth, I would have thought remove and replace (or recompact) might be the best/easiest option

 

[cvg]

depends on how deep you need the cement treatment. mixing with existing soil, in place is possible and cheap but not the best method for quality control. not sure why you would import expensive select granular and then mix with cement in place. better to remove existing and mix in pug mill and then place or just haul in pre-mixed soil cement from the nearest batch plant.

 

[Mercycity]

Dear Syble99.

We will appreciate if we can have the soil test results here then we can recommend the appropriate method to be used.
In our area we have clay soil and collapsible sandy soil. In Clay area we do replacement of the granular soil to a depth of 2B where B is a width of foundation if the rock is deep but such cases of 1.7m we do replacement up to the rock. In collapsible area we do pre-collpsing the soil or we stabilize with 3% Portland cement to form soilcrete and placed in a layer of 300mm or 150mm depends on compaction machine you have and each layer should compacted to achieve at least 90% Mod AASHTO density.

 

[Ron]

sybie99...it is impractical to successfully stabilize 1.7m of soil with cement. It is not likely that you can mix the material uniformly and get reasonable results. Further, if the poor soil is organic, it will impede the cement reaction and strength gain. For only 1.7m, I would consider removal and placement of select fill, compacted in thin lifts to provide a good bearing soil as moe333 noted.