One correlation for compression index that I've seen and used is as follows:
Cc=1.15x(10^-2)xWn (Wn=native moisture content in decimal form)
My experience with consolidation tests indicate this correlation may be conservative in my area (Wisconsin). In the book "Correlations of Soil Properties" by M Carter and S P Bentley (Pentech Press - London)it notes Cc can range from 10 to 15.
I assisted a buddy of mine in running some tests on peats from Minnesota a couple of years ago for his graduate work. We obtained peat samples (as undisturbed as possible) and ran consolidation tests along with SG, moisture, etc. The peat was very moist and moderately fibrous, probably bordering on what some would call "muck."
Here are some of the results we had:
initial void ratio 7.5
initial moisture 619%
SG (solids) 1.24
Cv (1.5psi) 0.8in^2/sec (over stress increments tested)
Cc 4.5
Cr 0.16
C(alpha) 0.07 to 0.147 (secondary-tertiary)
other info for our site:
initial overburden 1.5psi
preconsolidation stress 6.2psi
Keep in mind that it is difficult to obtain good quality samples of peat. We did the best we could, but the effects of the sampling certainly changed some of the insitu parameters. We also monitored settlement of an earth embankment on the same site using settlement plates. The actual settlement values of the new embankment were compared with the theoretical settlement estimate. The two agreed fairly well given the factors involved and using judgement as to how the consolidation parameters were altered during sampling. Hope this helps.
