Page 164 - Moving the Earth_ The Workbook of Excavation

BASEMENTS

4.4 THE WORK

FIGURE 4.3 Basement digging sequence.

pushed to the spoil pile. If a ripper or subsoil plow is available, it might be profitably used to break
up layers of dirt in advance of digging.

Ramping Down. A hydraulic dozer can cut hard soils, but will usually not cut a steep ramp
down without special handling. Figure 4.4(A) shows a dozer cutting down from a line in soft soil.
If digging is good, the blade will penetrate rapidly until maximum depth is reached. It will make
a level cut until the machine’s center of gravity moves over the cut. It will then fall forward, and
the blade will resume cutting until full penetration is reached, when it will level off again. Such a
series of steps makes an unsatisfactory ramp.
One way to make a smooth ramp, shown in (B), is to start it well back from the edge with a
gradual curve that is made steeper at the digging line. Cutting is then regulated so that the full
depth of penetration will be reached as the center of gravity crosses the steepened part of the
curve. Several passes are made in digging this ramp as indicated. This curve may be made steadily
steeper as depth increases, because the tractor itself is at a downward slope.
If the cut cannot be made far enough back into the bank for ramping in, the procedure shown
in (C) may be followed. Dirt is pushed out of the excavation into a steep pile, the dozer is backed
up on this, and is thus pitched down a steep enough angle to cut down sharply.

Piling. The area to be occupied by the pile should be calculated or guessed at, and the first piles
placed at its far side. Successive loads may be dropped toward the excavation, then a load carried
over these, pushing the tops off some of the heaps, and dropped at the back. The pile is thus built
up in a series of wedges, with their thin ends toward the excavation, as in Fig. 4.5(A).
Or the first load may be dropped at the near side of the intended pile, and the next pushed through
it with a raised blade so that the approximate upslope is established from the beginning, and suc-
cessive loads dumped off the back as in the (B) series. In either case the pile may show a tendency
to build toward the hole, and may have to be dug into severely to cut it back to proper distance.