soil shear strength after using PVD

[npthao121]

Dear All!
I am considering to soil improvement by using prefabricated vertical drain (PVD) method. The methods to calculate the final consolidation settlement, consolidation rate, PVD spacing ... are introduced quite clearly in most of geotechnical & foundation engineering textbook. But I could not find any lines or instruction regarding to how to calculate the shear strength of soil after a certain settlement is reached (let says 90% of final consolidation settlement reached) or pore water pressure is dissipated.

I understand that we have to make some field test & lab test to determine that parameter exactly, but how about the theory method?

Does anybody show me the way to calculate that parameter? Which book or which site contains necessary information? Also, by your experience with practical approach, how many times will the soil shear strength increase from the initial value? In my case the initial value of shear strength is 4 ton/m2 approximately, Will it increase to 8 or 10 ... ton/m2?

Thank in advance! All opinion will be highly appreciated!
Npthao121

 

[BigH]

You might want to redirect your query to the Geotechnical Thread - Foundation Engineering.

There was a technical note written back in 1975 I believe by N. Som regarding how to determine the increase in the undrained shear strength after consolidation. I have the paper, send your e-mail address to bohica@indiatimes.com and I will forward it to you - maybe, after a little procrastination (couple of days). I, too, am currently involved in similar exercise (Dr. Som is a consultant for the contractors on this one). I have very week soils and 9m high retaining walls to go on (RE Walls). Some data I found interesting from a soils boring programme here in the Calcutta area - undrained shear strength after long term (say plus 15 years) under 5m high embankment doubled the natural undrained shear strength where there was no embankment (and far enough removed, but adjacent, to not have been affected by the embankment.