Laboratory, 1 964; Toske, 1 969) . The larger tower, Stage One, is located in 

 1 00 feet of water and has overall dimensions of 1 05 by 1 05 feet. The struc- 

 ture is supported by sixteen 30-inch-diameter piles embedded 60 feet into a 

 medium dense to very dense gray silty sand. Pile capacity is 760,000 pounds. 

 Stage Two, the smaller tower, is 60 by 84 feet and is located in 60 feet 

 of water. Eight 24-inch-diameter steel piles arranged in a 60- by 60-foot square 

 support the structure. The upper 50 feet of sediment at the site contain medium 

 dense blue, green, and gray coarse sands. Below that depth is a dense gray silty 

 sand. Each pile, which has a capacity of 540,000 pounds, is embedded approxi- 

 mately 70 feet. No foundation problems have been reported. 



NELC Tower. An oceanographic research tower was constructed for 

 Naval Electronics Laboratory Center (formerly the Navy Electronics Labora- 

 tory, San Diego) in 1959 (LaFond, 1965). The tower is located in 60 feet of 

 water off Mission Bay, San Diego. The main tower extends 90 feet above the 

 waterline. Four 1 2-3/4-inch-diameter open-end steel piles support the struc- 

 ture. Maximum load on each leg is 1 40,000 pounds compression and 1 1 5,000 

 pounds tension. 



Subsurface exploration with probing and drilling techniques was 

 utilized at the site to establish sediment logs (Dames and Moore, 1959). 

 Water-jet probing reached 63 feet below the seafloor. A weathered conglom- 

 erate was encountered at that depth. Borings were made approximately 10 

 feet from the probings. A log of one of the borings is shown in Figure 38. 

 Undisturbed samples were taken and tested. In addition to routine tests for 

 soil engineering properties, the laboratory study established friction charac- 

 teristics between soil and steel. An effective angle of friction of 21 degrees 

 was measured between steel and medium- to coarse-grained sands with shells 

 (material found in the upper 30 feet), and a value of 19 degrees was measured 

 between steel and loam and fine-grained sands (material found below 30-foot 

 depth). No foundation performance problems have been reported. 



Tektite I Pile Guide System. During the on-site preparation phase of 

 the Tektite I program, a pile foundation system was used in 32 feet of water 

 for stabilizing and guiding a habitat-transporting barge (General Electric, 1969; 

 Hallanger, 1970). After the barge was flooded and lowered, the habitat was to 

 be floated off. A steel pile (about 21 inches in diameter) was driven to refusal 

 through each of the four corner guides on the barge. The barge was left moored 

 and floating in this condition overnight with plans to commence the controlled 

 flooding and lowering operation the following morning. Seas were reported to 

 be calm during the night; however, the next morning it was found that all four 

 piles had snapped off at the mudline. Subsequently, the piles were redriven, 

 and the flooding and lowering operation commenced immediately. This 

 approach was successful. 



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