A Systems Approach to Evaluation of Riprap and Armor Stone Sources

Abstract

The quality of riprap and armor stone for a particular project is occasionally determined through the use of ambiguous and subjective specification requirements. These requirements are often unrelated to true rock quality and result in placement of stone of unknown quality. Instead, a method for evaluation of the stone to determine the stone9s ability to provide adequate service life is needed. This method should include all aspects that have an effect on the service life. In other words, a systems approach that would take into account all aspects, even non-geologic aspects, of exposure conditions is required. The systems approach includes a complete geologic evaluation of the stone source; an evaluation of the project site in terms of climate and waterborne attrition agent; and a complete laboratory evaluation to measure block integrity and resistance to breakage, abrasion, and weathering. The systems approach should also include an evaluation of the specifications in terms of objectivity versus subjectivity plus a determination of the flexibility of the interrelationship between the specifications and the design parameters. This method has been successfully used for prediction of service life of several stone types and from igneous sources used on a breakwater project in British Columbia, Canada.