SEA-DEFENSE PROBLEMS - SUCCESS AND FAILURE OF SOME STRUCTURES

M. Dreyfous-Duoas Dreyfous-Duoas

Abstract


Considering the studies which have been published and the tests which have been made on models in past years, the author analyzes the reasons of failure or success on various defense works against the action of the sea. Groins and dry-wall breakwaters built since 1830 in the southwest of France are discussed.

Discussed first are the cases where the failure of the structure resulted from the nature of the construction. Structures of wood, masonry shell, and reinforced concrete are discussed, with solid masonry being considered as the most durable. Next these same types of construction are considered from the standpoint of their cross section. For groins, some permeability to sand is desirable; for dry wall breakwaters, a. small reflection of the waves is effective in causing a flattening of the beach. A flat rough slope is desirable as the face of a breakwater. Low permeability is also desirable.

With regard to the general layout of structures, the danger of long groins in the vicinity of channels , and of open type construction with longitudinal structures is shown.

The attention of engineers is directed to the importance of the ends of structures where the most critical conditions often, occur. In conclusion, construction features which are effective on a sandy coast are shown, and the difficult problems of a clay soil coast are considered.

Keywords


breakwater construction; groin construction; structure permeability

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