GRADING AND EXCAVATINGGrading and excavating are cutting the high spotsto grade and filling in the low spots. In cutting downthe high spots, enough suitable fill material may beremoved to fill in low spots. However, it may benecessary to develop other sources of fill material. Ifthe site is on hard and rocky terrain, loosen and breakthe soil with a dozer ripper. Before fill material can beplaced in low spots, a suitable foundation must beprepared. Material of a low-bearing capacity may haveto be dug up before the fill is placed.Base CourseThe base course distributes wheel load stressesfrom the surface pavement to the subgrade. Sincestresses in the base course are more concentrated thanin the subgrade, the base coursePlacement and CompactionWhen placing and spreadingon a prepared subgrade, start atmust be stronger.base course materialsthe point nearest the15-42source or at the point farthest from the source. Thenplace the material progressively away from or towardthe source, respectively. The advantage of workingfrom the point nearest the source is that haulingequipment can be routed over the spread material,which helps compact the base course and avoidscutting up the subgrade. An advantage of workingfrom the point farthest from the source is that thehauling equipment further compacts the subgrade,reveals any weak spots in the subgrade, and interferesless with the movement of spreading and compactionequipment.Base course compaction must produce auniformly dense layer, conforming in every way tospecification requirements. The thickness of the liftsshould NOT exceed that which can be compacted tothe required density. The thickness of the lifts isdetermined by the size of the compaction equipment,such as 6 inches for rollers and 3 inches or less whenusing tampers.NOTE: Optimum moisture content must bemaintained during compaction.
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