Consolidation Question

[nagatalluri]

Guys:

I have a question regarding the consolidation settlement calculations. We can estimate consolidation settlement given the soil properties and pre-consolidation pressure from the laboratory consolidation test. I am trying to calculate the time taken for 90% consolidation to understand how long does it take for 90% consolidation to occur. The reason is if the consolidation settlement is going to occur over a very long period of time then it shouldn't be a big deal. I used the equation below with time factor for 90% consolidation and selecting the Hdr (one-way or two-way drainage).

My question is which Cv (ft2/day) value should we use in this calculation. From the consolidation data we have Cv values corresponding to different loads 1000, 2000, 4000, 8000psf. Which one of these should be used in the estimation ?

I would appreciate your help in this regard.

Thanks
NT

 

[tsek]

Can someone correct me if I'm wrong? I think the Cv to use would be the Cv actually expected during the period of consolidation.

 

[BigH]

The OP correctly points out that the Cv value is not a constant value but depends on the load pressures actually used. If the added load does not go beyond the preconsoliation pressure or the quasi preconsolidation pressure, then the higher Cv values should be used (corresponding to the reconsolidation range). If the loads go beyond the maximum or apparent maximum pressures you should use the Cv value in the range of your applied loading.