in early 1 967, were 1 3 feet tall and had a 1 0-foot-square base. The bearing 

 surface area was approximately 1 5 square feet; the total weight of the struc- 

 tures in air was 650 pounds. The tests were conducted in 4,500 feet of water. 

 Sediments at the site were predominantly silts with shear strengths of 1 to 3 

 psi. One unit was removed in 1968, and the other will be removed later. 

 No excessive settlement was noted on the recovered rack. 



Figure 18. NCEL plate bearing device. 



NCEL Submersible Test Unit. Seven Submersible Test Units (STUs) 

 (Figure 19), which expose material specimens to the seafloor environment at 

 and just above the sediment line, have been placed by NCEL in water depths 

 of 2,370 to 6,780 feet (Jones, 1965; Hironaka, 1966; Reinhart, 1969). An 

 eighth STU was placed in 120 feet of water. The test units have remained on 

 the bottom for intervals of 4 to 24 months. 



In most cases, the STUs were supported by two strip footings. The 

 footings applied approximately 1 10 psf to the sediments. Sediments gener- 

 ally varied between silty clays and clayey silts. The soil at the shallow-water 

 location was predominantly sand size. 



32 



