Settlement of Model Seafloor Footings 



I 

 C 5 



3 6 



h- 



7 

 8 



9 

 10 



B 

 Mugu Lagoon s g 



\ 



% 



animals ^sT* 

 undermining \ 



footing \ 



\ 



.1 1.0 10 100 1,000 



Log Time (days) 



Figure 17. Typical settlement data from LOBSTER tests. 



NCEL Plate Bearing Device. The NCEL plate bearing device (Figure 

 18) was developed in 1965 to determine the short-term in-situ bearing pres- 

 sure and settlement response of marine sediments (Kretschmer, 1967). The 

 tripod frame is approximately 7 feet tall and has overall lateral dimensions 

 which allow it to fit within a 12-foot-diameter circle. Three articulated sup- 

 port pads (each approximately 2 feet by 5 feet) connected to the legs of the 

 framework transfer the weight of the device to the seafloor. Total pad bear- 

 ing pressure when fully loaded is approximately 200 psf . 



Circular and square bearing plates, ranging in diameter from 6 to 18 

 inches, transfer loads of to 5,500 pounds to the sediment during a controlled 

 penetration-rate test. About 100 tests have been performed in water depths 

 from 1 20 to 6,000 feet, at a number of sites off the Southern California coast. 

 No difficulties have been experienced with the foundation system for the device. 

 Results of the individual in-situ plate tests are discussed in detail by Kretschmer 

 (1967), Kretschmer and Lee (1970), and Taylor (1970). 



NASL Deep-Sea Exposure Arrays. The Naval Applied Science 

 Laboratory (NASL) placed two specimen racks in the TOTO as part of a 

 material evaluation program (Macander, 1969). The racks, which were installed 



31 



