jjsim, No sure if this will answer your question, but I had some correspondence with Professor Paul Mayne about this. I asked him a question related to a paper he wrote for the settlement analysis for a dormitory building in Atlanta (Unexpected but foreseeable mat settlements on Piedmont residuum). You can google and download it.
My question was about a paragraph in page 7:
"....Calculations of total displacements due to drained primary consolidation are best handled by either the classical evaluation of elastic stress distributions beneath surface foundations coupled with e-logσv' data, or elasticity theory using displacement influence factors and appropriate moduli."
My question was: does this means that elastic settlements analysis can be also used in lieu of consolidation settlement analysis? Are any other special considerations when conducting an elastic settlement analysis to predict settlements due to consolidation? My understanding is that consolidation analysis considers volumetric changes due to dissipation of pore pressures, however the elasticity approach does not consider variation in volume. Furthermore, I have been considering elastic settlements in saturated soils to be zero.
Here is Prof. Mayne's answer:
The short answer is that when you use consolidation theory, you also use elastic theory to calculate the stress distributions with depth. The stresses are used to position where you are on the e-log sv’ curves. An alternate (used moreso outside the USA) is to represent consolidation data as “constrained modulus” (See Lambe & Whitman 1979).
Otherwise, the (same) elastic theory can be used to obtain displacement influence factors – here, the stresses attenuated with depth are represented as strains
All things equivalent, you would get same answer, either using stresses or strains.
For the case study in the Piedmont geology, the coefficient of consolidation is high (sandy silt) and the time it took to build the dorm hi-rise (12 months) was essentially all drained settlements. That is, it consolidated quickly as the building was constructed (slowly).
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In Prof. Mayne's paper, you can see that he calculated the settlement using the elastic theory with the constrained modulus. My interpretation is that he used this approach because the Piedmont soils consolidate rapidly. On the other hand, I think that if you have fat clays, using the consolidation coefficients (Cv as f-d mentioned above), it is a better approach. So, basically, this is governed by the permeability of the soils and boundary conditions (again, as f-d mentioned above: the time of consolidation to occur).
