The other diver placed the transducer holder directly against the pile 

 in the designated regions of the pile. The engineer at the surface 

 viewed the movements of the diver holding the transducer, observed any 

 external damage pointed out by the diver with the video camera, and 

 monitored the ultrasonic signal from the receiver shown on the cathode 

 ray tube (CRT) screen. 



Communication was from the surface engineer to the video-equipment 

 diver. This allowed the engineer to inform the diver when a closer look 

 at damage was desired and when a reading needed to be repeated; but 

 with only one-way communication, the diver could not relay to the surface 

 engineer any problems encountered or visual observations pertinent to 

 the ultrasonic testing until after surfacing. 



The diver operating the transducer holder traveled from the marked 

 line at the waterline to the marked line at the mudline for each of the 

 quadrants on each pile. During testing two readings to check repeatabil- 

 ity were taken of each pile at 40 different locations. The data recorded 

 for each series of tests included the same information described in 

 Procedures of the NCEL Ultrasonic Laboratory Testing section of the 

 report. 



Field Test Results . Unlike the laboratory test piles, the harbor 

 test piles were not sectioned to determine the percent of cross-sectional 

 wood loss because these piles will remain in place for future inspection 

 testing. Therefore, the ultrasonic equipment can be evaluated only on 

 detection of external damage. 



For the four (three damaged and one new) harbor test piles inspected, 

 the regions of external damage were identified by combining visual, video, 

 and photographic data. Extent of the external damage (including length, 

 width, and depth of damage) was also determined. After location and 

 extent of damage for each pile were established, standard deviation of 

 the ultrasonic signal at these locations was evaluated. Based on ultra- 

 sonic laboratory test results, standard deviation of the ultrasonic 

 received signal over the 100-usec time interval held the greatest poten- 

 tial for correlation to the amount of cross-sectional wood loss. Thus, 

 only standard deviation of the ultrasonic signal received over the time 

 frame of 100 usee was investigated. 



Figures 17 through 19 give the ultrasonic field data collected at 

 and near the damaged regions. Regions of external damage were compared 

 to regions of no external damage. The location and dimensions of the 

 external damage are also shown in Figures 17 through 19, although the 

 damage is not to scale. This comparison showed the change in the standard 

 deviation with external damage; however, the amount of external damage 

 on all the piles inspected in the harbor was minimal (less than 15% 

 cross-sectional loss) . 



Figure 17 shows the relationship between the external damage of 

 pile 8 tested in the harbor and the standard deviation of the ultrasonic 

 signal received over 100 usee. Quadrants 1 and 2 of pile no. 8 were 

 analyzed; damage in quadrant 1 is substantial compared to that in 

 quadrant 2. Length and depth of damage are relevant to its detection 

 using ultrasonics. Therefore, the results in quadrant 1 (Figure 17a) 

 show a definite decrease in the standard deviation in regions where 



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