UNDERSEA TECHNOLOGY 



77 



NCEL in situ sea-floor plate bearing device after test in 1 200 ft of water. The 

 device is capable of determining the short-term bearing pressure and settlement re- 

 sponse of marine sediments. 



Soil tests are also being conducted in pressure vessels to determine the 

 effects of a high-pressure, low-temperature environment on the engineer- 

 ing properties of ocean bottom soils. The environmental effects were in- 

 vestigated through consolidation, direct-shear, and vane-shear tests on four 

 different ocean bottom sediments within pressure chambers at hydrostatic 

 environmental pressures up to 10,000 psi. The pressure chambers were 

 also refrigerated to provide a 1° to 3°C environmental temperature. Re- 

 sults obtained have confirmed that soO properties vary with increased 

 environmental pressure. 



Concrete foundations have been constructed in shallow water for many 

 years for bridges and dams. Two methods of placing concrete have been 

 used in the past. One method is by pumping concrete into forms which 

 have been placed on the ocean bottom. The second is by the assembly of 

 precast concrete units on the bottom. Both of these techniques will have 

 to be studied for application to deep water. 



The placement and recovery of heavy loads in deep water pose prob- 

 lems. The mechanics of raising and lowering heavy loads in the deep 

 ocean require special precautions but are within the state of the art. 



