Rock quality in coastal engineering

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Abstract The majority of coastal and shoreline defence structures use large quantities of rock in their construction which will be subjected to environmental conditions quite different from rock used for other purposes. Such materials are required to conform to specific size, shape and grading criteria by the designers of coastal defence structures and rock properties such as density will also be required for the design equations. The severity of the marine environmental conditions will also necessitate adequate levels of strength, abrasion resistance and durability. A quality assurance scheme for marine structures must take account of all these requirements. Test evaluations must be carried out at an early stage in the design process when alternative materials are being compared and again at the quality control stage of extraction as well as during the construction. Tests can be divided into four groups: those concerned with the geometric properties such as size, shape and grading; those concerned with intact rock strength and resistance to abrasion; with the intrinsic properties of the rock; and those related to durability characteristics such as weathering degradation. Many of the tests used to evaluate these properties were originally designed for aggregate materials, but recently two tests have been developed specifically for rock to be used in coastal defence structures. These procedures attempt to test those characteristics of the rock materials most affected by the degradation processes found in the marine environment and to offer a method of predicting the in-service performance of the rock with time.