local source. Material from new sources should be tested by the Government 

 for quality to determine acceptability. When the contractor desires 

 materials from a source not listed, or if the Government elects to retest a 

 source that is listed, suitable samples for quality evaluation should be 

 taken by the contractor under the supervision of the contracting officer. 

 Samples are generally delivered by the contractor to the nearest Corps of 

 Engineers laboratory for testing. 



No standard testing procedures have yet been developed for the determina- 

 tion of the quality of stone. The Waterways Experiment Station (WES) and 

 some Corps Division laboratories have devised tests to evaluate such 

 material, but the test procedures employed in these different laboratories 

 vary somewhat. In any case, judgment is necessary in applying the test 

 results. Any testing program for the determination of the quality of rock 

 for use as stone in coastal structures should include petrographic examina- 

 tion: determination of absorption and bulk and specific gravity {ASTM 

 Standard C97-47 (77) or C127-77}; a soundness test {American Association of 

 State Highway and Transportation Officials (AASHTO) Test T- 104-46 or ASTM 

 Standard C88-76}; and an abrasion test {ASTM Standard 535-69 (75)}. Other 

 tests that may also prove useful include a slaking or wetting-and-drying test, 

 and a freeze-thaw test. See Lutton, Houston, and Warriner (1981) for details. 



Properties contributing to durability of stone may be both physical and 

 chemical. Tests usually measure physical properties and therefore the 

 results provide only an indication of how chemical change has already 

 affected the stone, not the susceptibility to future chemical change. 

 Wetting and drying tests have been used to evaluate rock which disintegrates 

 badly as a result of chemical change, but there is still a question as to 

 what the test actually measures and what the results mean. Chemical 

 changes can best be evaluated by experience. 



The best data for evaluating stone to be used in coastal structures are 

 service records. If a stone has not been previously used, the quarry 

 should be visited and old surface outcroppings examined for signs of 

 weathering. 



b. Stone Size . To make optimum use of local materials, designs should 

 not only have a wide range of stone sizes to choose from, but also an 

 adequate number of classes within this range. Each class available for a 

 specific use should be limited in range. Physical limitations in the size 

 of armor stone that is feasible to use must also be considered. These may 

 be truck or highway capacity or the handling limits of the quarry equipment. 

 The geological structure of the rock quarry may also limit the quantity and 

 size of stone that can be obtained. 



The total weight or size of the armor units, the side slopes, the 

 density of armor material, and the degree of interlocking or wedging 

 between units are interrelated and comprise the principal factors in the 

 design of a stone structure. Armor stone may be rubble mound placed at 

 random, individually placed, or it may be rectangular blocks of stone 

 carefully fitted together. Several empirical formulas have been derived 

 for determining the size of armor stone required for the stability under 

 wave action. These are contained in the appropriate design manuals. In 

 the Hudson equation for design of armor stone {U.S. Army, Corps of Engineers, 

 Coastal Engineering Research Center (CERC) 1977}, the required size of 



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