(a) Direct Transmission 



(b) Indirect Transmission 



Figure 9. Two methods of ultrasonic through transmission. 



The number of ultrasonic signal readings taken along each individual 

 pile was dependent on the separation length of the transducers and the 

 length of the pile. However, the transducers were held at a fixed dis- 

 tance of 19 inches in the transducer holder during all laboratory tests. 

 Consequently, the number of readings taken was dependent only on pile 

 length. The maximum number of readings (100) was taken on the standard 

 pile. Approximately 20 readings were taken for each of test piles 5x, 

 4x1, 8335D, and 8323E. Every reading was repeated to evaluate reproduc- 

 ibility of test results. If discrepancies between an initial and second 

 waveform reading were observed, a third reading (or more, if necessary) 

 was taken in the same location. 



The data recorded for each series of tests included the following 

 information: 



• digitized ultrasonic signal waveform 



• location of the transmitter and receiver 



• description of the pile, including a sketch showing damage in 

 test locations 



• separation distance of the transducers 



• distance between transducers and pile surface 



• settings on the 7854 programmable oscilloscope 



• time, date, and location of the test 



• tape and file number 



• any changes in test setup or execution 



• comments, including noticeable changes in recorded waveforms 



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