Evaluation of the vertical motions of the dolosse armor units revealed that 

 some units moved upward slightly and some units slightly subsided. Average 

 movements of the armor units were on the order of about 0.061 m (0.2 ft). 



Eight broken units, four on each structure, were documented during the 1998 

 survey. Two of these were newly broken since the 1994 survey. One had a 

 chipped fluke, probably because of impact, and the other had a broken shank, but 

 was held together by reinforcing steel. A total of 17 broken units was observed 

 during the 1994 survey, but many were removed during the 1997 CORE-LOC 

 rehabilitation. 



Detailed position data obtained for the CORE-LOC armor units during the 

 current survey will establish a base from which to evaluate the movement of 

 these innovative armor units in the future. 



In general, methodology has been developed to assess the long-term response 

 of the jetties to their environment at Manasquan Inlet. Comparison of armor unit 

 data in future years will be conducted under the Periodic Inspections work unit 

 to gather data by which assessments can be made. Insight gathered from these 

 efforts will allow definite decisions to be made based on sound data as to 

 whether or not closer surveillance and/or repair of the structure might be 

 required to reduce its chances of failing catastrophically. Also, the periodic 

 inspection methods developed and validated for these structures may be used 

 to gain insight into other Corps' structures. 



The methodology used to determine concrete armor unit movement for the 

 Manasquan Inlet jetties was developed in 1984. It included monitoring the 

 movement of concrete armor units based upon a fixed target and sketching the 

 unit's position from the stereo model for current versus past periods. The scope 

 of the work presented herein was essentially the same as conducted previously to 

 achieve direct comparisons. Subsequently, however, procedures have changed 

 for armor unit position analysis at other projects. Currently three targets are 

 established, and the centroid of the armor unit is calculated. Not only target data 

 but also the armor unit's centroid is tracked through time. The position of the 

 axis of the armor unit relative to the vertical and horizontal planes is also 

 included in the analysis. The use of this methodology for future monitoring of 

 the armor units on the Manasquan Inlet jetties may be considered, time and 

 funding permitting. 



Chapter 4 Summary 



59 



