attempted, and during each test the penetrometer was prematurely triggered 

 hundreds of feet above the seafloor. On the first test the penetrometer 

 was arrested by the recovery line and returned to the tug. On the 

 second test it snapped the recovery line and was lost. It has been 

 hypothesized that uneven cable payout or the heaving of the tug caused 

 the premature triggering. In 1,200 feet of water, a penetrometer was 

 cast free at the water's surface to f reef all to the seafloor with no 

 lines attached to impede its progress. The signal from the sound source 

 was lost after the penetrometer reached a depth of about 450 feet. The 

 penetrometer seemed to be approaching a terminal velocity of about 80 feet 

 per second. It has been hypothesized that the signal was lost because 

 the acoustic output of the sound source reached its limit of overcoming 

 ambient noise and range distance. A calculation error caused the acoustic 

 output to be set too low. 



Table 1 . Comparison of Field-Measured Penetrations 

 to Penetrations Calculated From Data Taken 

 in 100 Feet of Water 



Test No. 



Measured Penetration, 



P (inch) 



m 



Calculated Penetration, 



P (inch) 

 c 



P /P 



m c 



1 

 2 

 3 

 4 



33 

 30 

 30 

 30 



30.0 

 27.6 

 26.4 

 26.4 



1.10 

 1.09 

 1.14 

 1.14 



The third series of tests was conducted from the CEL LCM-8 about 1 

 mile south of Port Hueneme in 70 feet of water. For these tests the 

 penetrometer was released at the water's surface and allowed to f reef all 

 to the seafloor with only a small cord attached to it. This facilitated 

 location of the penetrometer by divers so they could mark the penetration 

 and attach a recovery line. Four tests were conducted. Data gathered 

 were of very good quality (Figure 5) . Penetrations measured on the body 

 of the penetrometer and penetrations calculated from the data compared 

 excellently for two tests and reasonably well for the other two tests; 

 the comparisons are shown in Table 2. Penetrations were shallow because 

 the penetrometer was impacting at only 40 feet per second and because 

 the soil was a dense sand. Penetrations ranged from 2 to 3.5 feet. In 

 Figure 5 it is easy to identify changes in slope of the velocity trace 

 which are indicative of changes in deceleration. This, in turn, means 

 that, an observable change in resistance took place. This change is due 

 to both increased soil strength and the fact that more penetrometer in 

 the ground means more resistance. However, because of the shallow 

 penetration, it was not possible to separate these two effects. 



14 



