THE DESIGN OF BREAKWATERS USING QUARRIED STONES

Abstract

The majority of rubble mound breakwaters built in North America that use quarried stones in their armour layer contain either one or two layers of armour stone, one or two filter layers and a core of quarry run. Preparation of a design normally involves use of the Hudson equation and may be supported by physical model tests. Once the design wave conditions are defined the size of armour stones are only a function of the outer slope of the breakwater. In this paper an alternative approach to the design of quarried stone breakwaters is discussed. The basic principal involved in this concept is the use of locally available materials. It is established that the greater the thickness of the armour layer, the smaller the stones that are required to provide stable protection against wave action. Therefore, the thickness of the armour layer for a specific breakwater is determined by the gradation of the available armour stones and the incident wave climate. The final cross-section makes allowance for the practical considerations of breakwater construction. New concepts for breakwaters that have resulted from the use of this alternative design procedure are described. Construction of these breakwaters in 1983-84 has demonstrated that significant cost savings are obtained.