Intrinsic Compression Line Research Articles

Deep-Sea Sediment Compression Curves: Some Controlling Factors, Spurious Overconsolidation, Predictions, and Geophysical Reproduction

Oedometer tests have been carried out on 70 undisturbed surficial clays (at approximately 250 mm below the mudline), mostly collected by free-fall corers from sites widely scattered throughout the deep-sea North Atlantic. Acoustic measurements were also made, initially on contiguous samples and ultimately on the same sample using a geophysically instrumented oedometer which also collected electrical resistivity data. Apart from those quiescent areas 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 geotechnical-geophysical properties are dependent on the type of clay minerals present (and their ability to take in moisture), the sand-size fraction, and the quantity of carbonate present. Thus the pure clays have high compressibilities which decrease on the addition of coarse particles, while the converse is true for the acoustic parameters, these increasing with the sand fraction. Using the notion of the intrinsic compression line for all samples, and comparison to it of the measured compression curves, it is clear that, 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 construction of an in-situ sediment compression curve using the in-situ geophysical observations.

Intrinsic compression and swelling properties of a glacial till

Abstract The heterogeneous tills of Northrn England and Scotland are difficult to sample and test if using standard UK site investigation practice which was primarily developed for soft to stiff sedimented clays and sands. Application of empirical correlations and theoretical models to help select design parameters that were developed from standard tests on natural and reconstituted sands and clays may not be correct for tills because of their different mode of deposition and spatial variation in particle size and type. A geotechnical model is needed to explain the behaviour of tills which includes studies of the deposition and post-depositional processes, intrinsic properties of reconstituted till, and a database of results of natural till. Results of one-dimensional and isotropic consolidation tests on reconstituted tills, reported here, have produced compression data that define the intrinsic compression line (ICL) and a band encompassing swelling lines over a pressure range of 6 kPa to 5 MPa. The intrinsic normal compression curves for the reconstituted tills agree with the ICL, therefore developments in the application of the ICL can be applied to tills. Furthermore, a unique band, defining the intrinsic swelling properties, has potential for a baseline for the interpretation of mechanical tests on natural till.