The Problem 



As reviewed earlier in this report, the east and west breakwaters at Kahului 

 Harbor have undergone many repairs since the U.S. Army Corps of Engineers 

 became involved with the project in 1913. Most of the repairs were only 

 marginally successful before a unique breakwater capping method, referred to 

 as a concrete rib cap, was developed and tested on the prototype structures. 

 The ribs increase crest stability, reduce wave overtopping, provide buttressing 

 for crest armor units, allow ease of access for maintenance, and are less 

 reflective than solid concrete caps. Initially, rib caps were cast first, with 

 subsequent placement of the armor units. During construction, it was 

 discovered tiiat it was difficult not to leave a gap between the armor units and 

 rib cap on the upper sea-side slope. This procedure was later reversed (armor 

 units are placed first and then the rib caps are formed and cast in place) in 

 order to try to achieve better armor unit buttressing. Periodic photogrammetric 

 surveys of the Kahului breakwaters will aid in understanding the long-term 

 performance of the rib caps and their stabilizing effects on the armor units and 

 the breakwaters as a whole. They also will give a basis for comparing the 

 stability of areas which used different construction procedures. 



The 250-ft-long dolos armored breakwater constructed at the Laupahoehoe 

 Boat Launching Facility also utilized a concrete rib cap. Due to the interior 

 geometry of the structure, cylindrical reinforced concrete pipes were stood on 

 end and backfilled to provide a stable support for the rib cap. The structure 

 also used a unique toe entrenchment technique to assist in stabilizing the toe to 

 the 30-ton dolosse on the hard basaltic bottom. These unique design features 

 appear to the eye to be performing well structurally, and periodic photogrammetric 

 surveys will provide a basis for a long-term structural assessment of the 

 project and its possible application at other sites. This fits well with the 

 Periodic Inspections' hypothesis that "Periodic remote inspections can provide 

 long-term response data. " 



Purposes 



The purposes of the study reported herein were: 



a. To develop methods using limited land -based surveying, aerial 

 photography, and photogrammetric analysis to assess long-term 

 stability response of armor unit layers and concrete rib caps on the 

 Kahului and Laupahoehoe breakwaters. 



b. To conduct initial land surveys, armor unit breakage inspections, 

 aerial photography, and photogrammetric analyses to (1) test and 

 improve developed methodologies and accurately define armor unit 

 movement over the entire above-water armor unit fields, and (2) set 

 base conditions for breakwater armor units and rib caps, which can be 

 used as controls when the structures are revisited in the future under 

 the Periodic Inspections work unit. 



13 



Chapter 1 Introduction 



