obtained from houlders and cobbles in a.lluvium. Crushed or broken stone 

 includes all stone in which, the shape is- not specified. Stone fox coastal 

 structures should be free from laminations, weak cleavages and be of such a 

 character that it will not disintegrate from the action of air, seawater, or 

 handling and placing. A stone of high specific gravity is desirable because 

 it increases the resistance to movement by the action of waves or currents. 

 Durability of stone, can be affected by its mineral composition, texture, 

 structure, hardness, toughness and resistance to the effects of wetting and 

 drying and freezing and thawing. Stone is generally classified as granite, 

 basalt and related rocks, limestone and marble, sandstone and miscellaneous 

 stone. 



While no standard testing procedure has yet been developed for the 

 determination of the quality of stone, other than past experience with 

 specific quarries, there are testing programs that are used. With any 

 testing program for the determination of the quality of rock, judgment is 

 necessary in applying and interpretating test results. This requires a great 

 deal of experience and should be left to geotechnical experts. Any test 

 program should include petrographic examination, determination of absorption 

 and bulk specific gravity (ASTM Standard C97-47 or C127-77), a soundness test 

 (AASHTO T-104-46 or ASTM C88-76) and an abrasion test (Los Angeles rattler, 

 Wetshot rattler or ASTM 535-69 {75}). Other tests may prove useful depending 

 on specific project requirements. Properties contributing to durability of 

 stone may be both physical and chemical and chemical changes can best be 

 evaluated by experts . 



(2) Stone Size and Shape . Stone size is important in coastal 

 structures. Bedding layer material, core rock or quarry-run material is 

 usually 15 to 20 centimeters (6 to 8 inches) or less. Underlayer stone may 

 range from a few kilonewtons to about 30 kilonewtons. Armor stone is the 

 largest size and ranges up to 220 kilonewtons. Stones larger than about 220 

 kilonewtons are generally not easily handled. While the three ranges of 

 stone sizes are required for the different parts of a rubble-mound structure, 

 an adequate number of classes within each range is also necessary. In 

 fitting stones into a structure, the shape as well as the size is important. 

 Design requirements usually specify that the greatest dimension of an indi- 

 vidual stone be no more than three times its least dimension. 



In addition to the physical properties of stone, the method of quarrying 

 will also determine the size, range and classes within a size range that are 

 produced. Depending on the area topography, a quarry will generally be 

 developed as either a side hill or a pit-type operation. The size of quarry 

 face developed in any given operation is usually determined by the thickness 

 of the formation. The method of blasting and the type of explosive, as well 

 as the geological and physical characteristics of the material, will determine 

 the degree of fragmentation that will result from the quarry operation. 

 Generally a high powder factor (quantity of explosive per unit volume of 

 rock) will produce a greater degree of fragmentation than will a lower powder 

 factor. Also, greater fragmentation will be achieved in a massive rock by 

 using a large number of small diameter holes at close spacing than by using 

 large diameter holes at greater spacing. It also appears that best fragmenta- 

 tion is achieved when holes are detonated individually rather than simulta- 

 neously . 



375 



