Design and test of a torsional vibratory core sampler for marine sediments

Studies of marine sediments for geological, biological or engineering purposes is an area of increasing importance as more investigations are directed toward surveys of submerged bottoms of oceans, lakes, and rivers. This paper summarizes a project initiated in Jan. 1969, to design, develop, and test prototype coring equipment for marine environments. The torsional system of vibration offers several specific advantages with respect to penetration of a marine sediment probe: (1) shear stresses, for inducing tixotropic transformation in the sediment, are obtained without involving the preload mass in the vibratory system, by swivel mounting; (2) a sawing action is provided at the leading edge of the probe; and (3) a square tube in torsion generates an envelope by soil compression, both outside and within the tube. The square tube has further advantages in facilitating construction of a core retainer and in allowing transverse sampling for daughter cores through ports in the sidewall.