Total unit weight 103to105pcf 



Specific gravity 2.73 to 2.76 



Water content 50% to 80% 



Void ratio 1 .40 to 1 .90 



Unconfined compressive strength 1 .0 to 4.3 psi 



The seafloor topography was relatively smooth with slopes varying from 3 to 

 20 degrees. 



Each hydrophone structure included: (1 ) an open space-frame, with 

 a major lateral dimension of 30 feet, for supporting the individual hydrophones; 

 (2) a universal joint and buoyant sphere for maintaining the hydrophones on 

 the space-frame in a fixed, stable plane; and (3) a base for anchoring the con- 

 figuration. The bases for the first structures were concrete cubes with 3-foot 

 sides. The newer hydrophone structures have a 3-foot-square open box base. 



Immediately after the first structures were placed, difficulties were 

 noted with one (Linger, 1969). An anchoring base and its attached frame slid 

 down a 10- to 15-degree slope dragging an umbilical cable. A lateral distance 

 of approximately 1 ,000 feet was traversed. The possibility of sliding was 

 reduced on the seven more recent structures by designing the base with a hol- 

 low interior and open bottom so that the perimeter became a cutting edge. 

 During emplacement of these seven, the bases were dropped from approxi- 

 mately 50 feet above the seafloor in order to increase penetration into the 

 sediments. It was intended that any downslope motion would be resisted by 

 the lateral stress mobilized against these "keying edges." No subsequent dif- 

 ficulties with foundation performance have been reported. 



Other Acoustic Ranges. The University of Miami installed a transducer 

 and two receivers for measuring environmental fluctuations in the Straits of 

 Florida between Miami and the Island of Bimini (Sykes, 1969; Steinberg, 1969). 

 Bottom sediments were hard, and equipment weights were low. No foundation 

 performance problems have been reported. 



The Lockheed Ocean Laboratory, San Diego, installed a hydrophone 

 system off San Clemente Island in the early 1960's (Inderbitzen, 1969). The 

 purpose of the range was to demonstrate the Laboratory's ability to perform 

 oceanographic work. A concrete block base held the hydrophone array in 

 place for 3 months without incident. 



Other similar structures have been used by Woods Hole Oceanographic 

 Institute, Columbia University, Bedford Institute of Oceanography, and on 

 Project CAESAR. No foundation problems have been reported; however, in 

 these cases, the only information available is that the structures exist. 



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