Cemented marine soils exhibit behavior not found in comparable land soils and the evaluation of their engineering properties requires special procedures. This paper focuses on methods for evaluating the engineering properties of cemented deep-ocean soils using data from cores taken in the Southern Labrador Sea. Selected empirical relations are presented and discussed to elucidate the affect of carbonate cementation on engineering soil properties related to problems in ocean engineering. Such empirical relations are useful in preliminary analysis and in extending the results of a laboratory testing program.


During recent years several hundred feet of deep-ocean sediment core has been tested in the Geotechnical Laboratory at the University of Rhode Island. In addition to routine identification tests, a number of one-dimensional consolidation tests and travail strength tests have been performed. Travail tests have been conducted at pressures both above and below computed overburden pressures and apparent overburden pressures as determined from one-dimensional consolidation tests.

In the course of testing and analyzing these sediments, certain characteristics have become apparent. Of particular interest is the apparent over consolidation of many samples when the normal reasons for over consolidation are absent. Noorany and Gizienski (12) have discussed such behavior, particularly the relationship between delayed consolidation and apparent over consolidation. In addition to delayed consolidation actual cementing of soil particles through precipitation of cementing agents at particle contacts is possible. The causes of apparent over consolidation are interrelated, and one factor will not control in all cases.

When large amounts of data are collected, means of insuring the reliability of the data are necessary. Wilun and Starzewski (17) suggest the use of graphical correlation in which a "leading parameter," such as water content, is systematically compared with other parameters such as shear strength and compressibility. In this way a continuous check of the testing program is available and empirical correlations between parameters such as plasticity index (PI) and the ratio of untrained shear strength to overburden pressure (c/p) may be developed.

Data to be presented herein as well as data in the literature (8) indicates that carbonate content is an important geotechnical parameter in some deep-ocean sediments. As already mentioned, carbonates may precipitate at interpretable contacts causing rigid bonds with the obvious effects on strength and compressibility. Carbonate contents may also be related to other anomalous behavior in marine sediments as reported by Silva (14).

The carbonate contents reported herein were determined using the acid dissolution' technique (1). While the actual values may be too high (13), the percentages determined by this method serve as an index of the amount of carbonate present.

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