In-Situ Determination of the Strength of Marine Soils

Minor emphasis is placed on three topics: (1) marine soil properties, distribution, and state of stress; (2) in-situ testing methods, in which it is noted that only the cone penetrometer, piezocone, and field vane are routinely used by the offshore geotechnical industry; and (3) the drilling-wireline and the seabed deployment systems and their principal subsystems. Major emphasis is placed on two topics: (1) quality assurance of in-situ testing and (2) a discussion of test descriptions and test standardizations, particularly with respect to the field vane and cone penetrometer. Some of the more important findings are that the in-situ strength distribution, particularly in the horizontal plane, is not well known; industrial offshore in-situ testing is a complex system involving ships, operational stability, deployment equipment, drilling or seabed subsystems, and probes and sensors; and how in-situ strength may be degraded by drilling and in-situ testing procedures. In addition, the offshore geotechnical industry recommends that full test descriptions be provided, unless supplemented or replaced by recognized standards. Only the field vane and cone penetrometer tests are reasonably standardized. The principal conclusion is that in-situ strength testing usually involves fewer significant problems than sample collection and laboratory testing.