Arctic slope protection structures are a developing technology. As such, protection techniques are often used in the arctic that do not see wide use in other areas of the world. Thus, the performance of these systems is not fully known, especially when the role of ice in causing damage to offshore structures is concerned. All this points to a need for a monitoring and inspection program to document post-construction status, to define areas where protection may not be adequate, and to re-examine the structure for needed repairs after summer storms and in the spring after breakup.
Techniques for the inspection of the submerged portions of structures by side scan sonar have been developed, field tested, and utilized in the arctic. Side scan records of sand bag slope protection and other shore protection structures have been obtained. Real-time side scan records were reviewed and interpreted and certain portions of the under-water structure were "spot check" inspected and filmed by a diver-deployed video inspection system.
This paper is based on the preliminary investigations leading up to the inspection techniques and the subsequent insights achieved by field tests and applications in the arctic. The paper outlines the systems and technology available, describes in general the results obtained, and points out various applications.
Since the construction of the first artificial islands in the Beaufort Sea, sand bags overlying a filter fabric have been the typical method for shore protection. While sand bags have been sufficient for many applications, it is becoming important to establish proper design guidelines in order to define the limits of satisfactory sand bag performance and to explore ways to improve their performance. The uniformity, orientation, and integrity of the cover on the underwater sand bagged slopes have been found to be important factors governing their stability under wave attack.
Neat and uniform sand bag placements can be achieved near and above the waterline (see Figure 2), however, the bags cannot be placed in the same manner on the underwater portions of the island due to turbidity in water column and the need for rapid construction. In view of the importance of the underwater bag integrity to stability of the slope protection structure, a specific course of action is indicated: to perform inspections of the existing sand-bagged islands which are exposed to substantial wave activity in order to assess the integrity of the underwater slope protection. This will serve to identify the locations and magnitude of potential slope protection problems so that appropriate measures might be planned.
Inspection of the underwater slope protection in the Beaufort Sea involves several problems. First, during virtually all of the open water season, the underwater visibility is usually less than only a few feet. Second, because of the large size of the bags (about eight feet long) and the large extent of the underwater slopes involved (half an acre or more) it is necessary to view the slope from some distance in order to assess the integrity of the slope protection. These factors eliminate several techniques as effective methods of inspection. Direct observations by divers is limited to ineffective close range observation.
