economical haul distance is the mass diagrammethod.A mass diagram is a graph or curve on which thealgebraic sums of cuts and fills are plotted againstlinear distance. Before these cuts and fills aretabulated, the swells and compaction factors areconsidered in computing the yardage. Earthwork thatis in place will yield more yardage when excavatedand less yardage when being compacted. An exampleof this is sand: 100 cubic yards in place yields 111cubic yards loose and only 95 cubic yards whencompacted. Table 10-1 lists conversion factors forvarious types of soils. These factors should be usedwhen you are preparing a table of cumulative yardagefor a mass diagram. Cuts are indicated by a rise in thecurve and are considered positive; fills are indicatedby a drop in the curve and are considered negative.The yardage between any pair of stations can bedetermined by inspection. This feature makes the massdiagram a great help in the attempt to balance cuts andfills within the limits of economic haul.The limit of economic haul is reached when thecost of haul and the cost of excavation become equal.Beyond that point it is cheaper to waste the cut fromone place and to fill the adjacent hollow with materialtaken from a nearby borrow pit. The limit of economichaul will, of course, vary at different stations on theproject, depending on the nature of the terrain, theavailability of equipment, the type of material,accessibility, availability of manpower, and otherconsiderations.The term free-haul distance means a distance overwhich hauling material involves no extra cost. Thisdistance is usually taken to be about 500 feet–meaning that it is only for hauls longer than 500 feetthat the limits of economic haul need to be considered.Table 10-1.—Soil Conversion Factors (Conversion Factors for Earth-Volume Change)10-11
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