An Analysis of Sediment Shear Strength.

The part played by laboratory testing in the successful application of underwater soil mechanics to problems concerning ocean engineering depends both on the uniformity of the natural strata and on the skill and experience of the engineer. The empirical relationships developed in terrestrial soil mechanics for designing foundations and determining soil mass stability are based to a major extent on triaxial tests, while virtually all data on marine sediments have been acquired using vane shear tests. The standard vane shear test has been most widely used because it can be performed quickly, with a minimum of sample disturbance, and the equipment is relatively simple and inexpensive. This study concerns the determination of laboratory shear strength for a marine soil, and evaluates the relationship between the vane shear test and triaxial test results. For the particular sediment tested (a clayey silt), the initial tests indicate the vane shear peak strength to be 10% of the triaxial test peak shear strength, however, thus far, the writer has found virtually no correlation between the two tests.