S. Buchan et Dt. Smith, Deep-sea sediment compression curves: Some controlling factors, spurious overconsolidation, predictions, and geophysical reproduction, MAR GEORES, 17(1), 1999, pp. 65-81
Oedometer test have been carried out on 70 undisturbed surficial clays (at
approximately 250 mm below the mudline), mostly collected by free-fall core
rs from sites widely scattered throughout the deep-sea North Atlantic. Acou
stic measurements were also made, initially on contiguous samples and ultim
ately on the same sample using a geophysically instrumented oedometer which
also collected electrical resistivity data. Apart from those quiescent are
as below the carbonate compensation depth, such as north of the West Indies
where very fine clays exist, most of the samples are silty clays whose geo
technical-geophysical properties are dependent on the type of clay minerals
present (and their ability to take in moisture), the sand-size fraction, a
nd the quantity of carbonate present. Thus the pure clays have high compres
sibilities which decrease on the addition of coarse particles, while the co
nverse is true for the acoustic parameters, these increasing with the sand
fraction. Using the notion of the intrinsic compression line for all sample
s, and comparison to it of the measured compression curves, it is clear tha
t, contrary to some previously held ideas, most deep-sea clays are normally
consolidated; the addition of carbonate has the effect of creating an open
, stronger sediment skeleton. Interestingly, where information is available
, the variation with depth of a sample's acoustic velocity follows the void
ratio/pressure relationship of the compression curve. This allows the cons
truction of an in-situ sediment compression curve using the in-situ geophys
ical observations.