Seafloor penetration tests : presentation and analysis of results / by H.J. Migliore and H.J. Lee.

Abstract

A series of eleven in situ penetration tests was conducted by the Naval Civil Engineering Laboratory (NCEL) at two seafloor sites. The objectives of these tests were to illustrate the capabilities of existing penetration evaluation equipment and to acquire data for use in evaluating a series of proposed penetration prediction techniques. The tests consisted of allowing two types of objects to free-fall into the seafloor with the accelerations experienced by the objects during penetration being recorded mechanically. The resulting data were subjected to a regression analysis which yielded information about the penetration mechanism but no practical results. This was followed by a physical analysis based on static soil mechanics relations. The latter analysis was shown to yield predictions of penetration depth which were within 50 percent of the measured values. A suggested prediction technique based on this analysis is presented.

Measurements and Estimates of Engineering and Other Physical Properties, Leg 19

“…The NCEL vane has the capacity of operating at a variety of rotation speeds, although for Leg 19, the rotation speed of 83 degrees/min was chosen. This speed is significantly higher than the 6 degrees/min usually used in vane shear testing and it has been shown (Migliori and Lee, 1971) that variations in rotation speed of this magnitude can cause changes in measured strength on the order of 10 percent. The faster speed was chosen because it permitted the performance of many more tests and anticipated changes in strength resulting from disturbance (at least 100%) were much greater than any possible rate effects.…”