requirements for disposal of the spoil. In all cases, thestarting point and digging sequence must be planned, sothe backhoe conveniently works itself out into the clear.Improper procedures will not only trap the machine, butcan lead to situations where the machine cannot bepositioned to complete the job. In this situation, handdigging may be required to complete the excavation.An accepted starting and digging sequence that canbe followed for excavating a small foundation is shownin figure 9-63. Remember that digging time is lost eachFigure 9-63.—Foundation excavation.time the machine must be moved. The digging sequenceis planned, so a maximum amount of spoil can beexcavated before the machine is moved to the nextposition.For example, the first cut is to be made on the westline (fig. 9-63, view A). The starting position of themachine would be on the west line at a point where theboom and dipper stick will reach the northwest corner.The machine and boom are lined up parallel with thewest cutting line, so the outer edge of the bucket isexactly in line with the cutting line.The first cut is made by digging a ditch along thewest cutting line. The ditch should be dug to its full depthand grade. This depth and grade serves as a depth guidefor the other cuts. When the west wall has been dug asclose as possible to the machine position, you thenswing the boom to reach near the center of the northcutting line. The second cut, as shown in figure 9-63,view A, is made by digging a trench back from the northwall. The material cut in the angle formed between thesetwo trenches is removed in layers until the bottom gradeis reached.NOTE: Ensure that the desired grade is reachedbefore moving the backhoe.The backhoe is then backed up into the secondposition, as shown in figure 9-63, view B. Digging iscontinued in steps, as shown in figure 9-63, view A. Theditch is dug first along the west line. The boom is thenswung around to cut the angle trench and the material isremoved to grade. Digging is continued in this manneruntil the south line is reached.The backhoe is then moved to the unexcavatedportion of the south line. This position is shown in figure9-63, view C. Here, the backhoe is positioned with thebucket in the excavation at the southwest corner to beginthe ditch along the south cutting line. Again, after theditch is dug along the cutting line, you should swing theboom toward the center to remove as much spoil aspossible from this machine position.You should continue to move the backhoe aroundthe excavation, repeating the digging steps until all fourcutting lines are cut and the spoil removed. To make thefinal cut to remove the material, you may have toposition the machine at the edge so the bucket can digstraight up. This cannot be done unless the soil type isknown to have good-bearing qualities. Cave-ins willresult if the soil will not support the weight of themachine.NOTE: Before excavating at a jobsite, alwaysconsult with the project supervisor or crew leader aboutyour excavation plans. Keep in mind that the area you9-28
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