The use of soil fabric studies in evaluating the strengths of clays in a North Sea site investigation

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Abstract
Soil fabric features influence both the large-scale engineering properties and measurements made in laboratory and field tests. The effects on the large-scale parameters and different types of tests can vary appreciably. In the absence of relevant full-scale test data from the site being investigated, fabric studies can play a vital role in the evaluation of design parameters from laboratory and small in situ tests. This is especially the case where relationships between test and large scale behaviour have previously been obtained in soils with similar fabric features and stress histories. The potential value of fabric studies is particularly important in offshore investigations where large-scale in situ tests are not feasible and even the data from laboratory and small in situ tests are severely limited. During a major investigation for a gravity platform in the Norwegian sector of the North Sea in 1981 it was found that the relationships between the results obtained from the different types of tests did not fit into the patterns previously found at other North Sea sites. The need to explain these anomalous results and the availability of adequate numbers of good quality samples provided an excellent opportunity to make extensive observations and measurements of the soil fabric features and to use them in the interpretation of the test data and the evaluation of design parameters. This paper describes the detailed macro-and micro-fabric studies which were made and their role in explaining the anomalies in the test data and in the evaluation of the design parameters.