Table 7. Summary of Long-Term Loading Data From Spheres Tested in Pressure Vessel (after Ref 5) 







Sustained 

 Pressure, 



Ps 



(psi) 



Uniaxial 



Predicted 



Relative 







Sphere 

 No. 



Condition 

 of 



Compressive 

 Strength,^ 



Implosion 

 Pressure, 



Load 

 Level, 



Time to 

 Failure 



Comment 



Concrete 



fc 



pP 



Ps 



(day) 









(psi) 



(psi) 



^L 







CWL-5B 



wet 



2,280 



7,900 



2,395 



0.95 



0.14 

 (200 min) 





CWL-6 



wet 



1,670 



6,740 



2,040 



0.82 



41.82 



Test intentionally 

 terminated 



CWL-7 



wet 



1,940 



7,170 



2,170 



0.89 



0.06 

 (90 mm) 





CWL-8 



wet 



1,845 



7,210 



2,185 



0.84 



0.47 

 (680 min) 





CWL-9B 



wet 



1,905 



7,440 



2,255 



0.84 



3.77 





CDL-10 



dry 



2,405 



9,420 



2,855 



0.86 



0.19 



(270 mm) 





CDL-11 



dry 



2,065 



7,940 



2,415 



0.85 



20.92 



Test intentionally 

 terminated 



^Strength given for weaker hemisphere. 



bn.P 



0.303 f^ obtained from short-term loading tests. 



Permeability 



Table 1 gives the change in nunnber 

 of chain links suspended off the seafloor 

 by the spheres. The change in link count 

 was due to a loss of buoyancy by the 

 spheres because of weight gain fronn 

 water absorption and permeability. The 

 loss of buoyancy was converted to a 

 volume of seawater taken on by the 

 spheres. 



Total water intake by a sphere 

 included the quantity of seawater 

 absorbed by the concrete and permeated 

 through the wall. The quantity of 

 seawater absorbed by the concrete was 

 calculated by assuming 3% by weight 



absorption. Three percent absorption 

 was determined for identical concrete by 

 extrapolating data obtained at 550 feet 

 (l68 m) pressure head for 86 days (Ref 

 li) to a time period of 3 years when it was 

 estimated that absorption was complete. 

 For Sphere no. 12, which was 

 uncoated, it was predicted from the 

 chain link count that the interior 

 contained 1.38 cu ft (39 liters) of water. 

 The actual measured volume of water 

 was 1.2^^ cu ft (35 liters). This close 

 prediction of the actual permeated 

 seawater not only indicates the 3% by 

 weight absorption is a fair estimate, but 

 also that the initial calculations of the 

 original number of chain links suspended 



30 



