Statistical Correlations of Engineering Properties of Clay Deposits

ABSTRACT A thorough statistical study of engineering properties of the Gulf of Mexico clays was conducted. An extensive amount of data covering a wide range of offshore clay properties was assembled and analyzed. The data represent the results of strength, consolidation and classification tests on clay samples from the upper coast of the Gulf of Mexico. The analysis included a total of 759 samples from depths ranging from about 2 ft. to 446 ft. The samples were obtained by 65 undisturbed-sample borings drilled in water depths varying from 3 ft. to 382 ft. Several forms of single and multiple correlations were developed among the engineering properties of Recent and Pleistocene offshore clay deposits. The established relationships were evaluated statistically. The significant correlations were compared with similar equations developed earlier by other investigators for offshore and on land clay formations. It is concluded that several valuable relationships exist between certain properties of Gulf of Mexico clays. Examples are correlations between the plasticity index and liquid limit, between the undisturbed cohesion and preconsolidation pressure, and between the compression index and liquid limit. These correlations agree favorably with results of previous studies. The consolidation and strength characteristics of the clays can be practically predicted from the index properties of the soil. Equations relating the compression index, preconsolidation pressure, remolded and undisturbed cohesion of the Recent and Pleistocene clays, with such soil properties as the liquid limit, moisture content and unit dry weight, are reported. INTRODUCTION Significance Correlations which establish reliable relationships between soil properties can be quite useful in soil engineering practice. The value of such correlations is even greater in connection with offshore studies due to the adverse conditions faced in collection of soil data. Securing sufficient information in marine soil investigations involves considerable cost and difficulty. The prediction of consolidation, strength and other characteristics of undisturbed offshore deposits from the index properties of the soil is particularly helpful. Previous Studies Earlier investigations have shown that there are reliable correlations between soil properties of the Mississppi River deposits (15). McClelland (11, 10) studied the engineering characteristics of the Gulf of Mexico soils and established valuable relationships between the properties of offshore clays. Casagrande (3) related the plasticity index and the liquid limit of fine-grained soils for classification purposes. Skempton (16) correlated the compression index of remolded clays with their liquid limits; Terzaghi and Peck (17) developed a similar relationship for undisturbed, normally consolidated clays of moderate-to-low sensitivity. Objectives and Scope This study is a continuation of earlier work on correlation of engineering properties of the Gulf of Mexico clays to confirm and to extend these relationships. An extensive volume of data was analyzed statistically to determine interrelationships among the offshore clay properties.