Figure 11-28.-Spreading.Figure 11-29.–Culvert backfilling.SPREADING.— Dozers are ideal for spreading fillmaterial brought in by haul units (fig, 11-28). Positionthe blade in a straight position, so the material is drifteddirectly under the cutting edge.BACKFILLING.— Backfilling is the process ofreplacing excavated earth, as shown in figure 11-29.When a culvert is backfilled, the dozer should not crossthe culvert unless there is at least 12 inches of compactedmaterial on top of the culvert. If a bulldozer is used tobacfill a culvert, the best method is to make diagonalpasses over the material, ending each pass with a swingthat brings the blade in line with the culvert.The angle blade is preferred for bacfilling atrench, because material can be side cast into the trenchwhile maintaining a steady forward motion, as shown infigure 11-30.Figure 11-30.Trench backfilling.When a pipe trench is bacfilled, fine material isplaced around the pipe and coarse material above it, sothe pipe is supported by well-compacted material.However, covering the pipe to full depth in short lengthsmay concentrate weight and break pipe joints; therefore,cover the pipe in successive layers, rather than all atonce.NOTE: Be careful in pipe trench bacfilling toavoid dropping large rocks directly on the pipe.FINISHING.— Whether clearing or spreadingmaterial on a roadbed, no job is completed until it hasbeen smoothed and drainage is established. This iscalled finishing and should be done at the end of eachShift.Blade the job lightly with about a half of a blade ofdirt. This fills in any low spots or holes. Leave awindrow on the side that you are working toward. At thestart of the next pass, cover half the blade width.Continue in this fashion over the project or section ofthe project you have worked that day before you shutdown for the day. Finishing the project in this mannersupports drainage and prevents having to walk overpiles of dirt or through mudholes.DitchingRough ditching can be done with a dozer by makinga series of overlapping passes at right angles to the lineof the ditch. A “V” type of ditch can be dug with a dozeras follows: First, buildup a windrow along the edge of11-15
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