fore important that the sequence of operations, type of equipment, rate of 

 production, and number of times the material is handled be evaluated and 

 controlled. 



The best time to control the gradation of quarried stone is during the 

 quarrying. Control of gradation to meet specifications is usually carried 

 out by visual inspection. In order to calibrate the judgment of the in- 

 spector, it is very helpful to establish, at a convenient location in the 

 quarry, a pile of stone with the desired gradation. This standard pile 

 should contain 44.5 to 89 kilonewtons (5 to 10 short tons) of material, and 

 should be formed by measuring and selecting the individual stones to be 

 combined in the correct proportion. In the case of riprap, or other large 

 stone, there may need to be a larger volume in the pile used for visual 

 calibration. 



Some projects may permit the use of "quarry run"; i.e., whatever 

 quality and gradation of stone that may come from the quarry without any 

 special control or processing. However, when specifications are being 

 prepared, it is very important to the project owner that any limitations be 

 carefully identified. He may expect quarry run to be the product of very 

 cautious blasting using controlled methods and he may encounter either a 

 design problem or contractual problem if entirely different methods are 

 used by the contractor. 



It should be anticipated that even fresh rock will contain up to 5- 

 percent fines due to blasting and careful handling, and that the quantity 

 of fines can be increased substantially depending on the equipment and 

 methods used in handling. Commonly, another 5-percent fines are generated 

 in crushing and processing. Of course, the greater the number of times the 

 material is handled and processed, the greater the percentage of fines 

 generated or material lost (such as in stockpiling) . 



To minimize further degradation of the materials, the contractor should 

 use large-size loading equipment in the borrow area and rehandling should 

 be kept to a minimum. With large- size loading equipment, it should not be 

 necessary to use dozers on the muck pile. Such use can be expected to 

 cause a significant degradation of the stone particles. Further, the use 

 of large loading equipment minimizes the need of using excessive quantities 

 of explosives to provide excessive rock fragmentation. 



Excavation of materials is usually carried out with power shovels, drag- 

 lines, scrapers, front-end or side-delivery loaders (Sherard, et al . , 1963). 

 In quarries, the most common items of equipment are shovels and front-end 

 loaders. Power shovels provide the greatest reaching capacity and greatest 

 digging capacity in poorly fragmented or poorly loosened materials (Fig. 5). 



This digging capacity is important when production of large stone is 

 desired for riprap. The reaching capacity often contributes greatly to 

 overall efficiency by permitting higher benches. Large front-end and side- 

 delivery loaders are probably the most economical in a medium-size operation 

 producing crusher feed, where blasting is designed to produce fine fragment- 

 ation, and on those projects where high mobility is desirable. (It is a 

 slow process to move a large shovel any distance.) Small front-end loaders 

 are probably the least efficient, since they can only handle small-size 



38 



