Page 201 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

DITCHING AND DEWATERING 5.3

While digging downhill is easier, the working end of the trench may fill with water if the
ground is wet or the job stands unfinished during a rain. Underwater work is sloppy, inaccurate,
and often unstable.
Starting. The machine is placed so that it is centered on the centerline of the ditch, with the tracks
or wheels parallel to it, and the bucket extended to almost its full reach and resting on the starting
point, as in Fig. 5.1(A).
Actual digging procedures with the different types of hoe are described in Chap. 13.
Briefly, the soil is taken out in layers down to the required depth. The starting point may be
squared off with a vertical face from top to base. The bottom is smoothed off and checked for
depth as it is made.
When the desired depth has been obtained along the space the shovel can reach, it is walked
away from the ditch from 2 to 12 feet, and a section of that length excavated. Short moves are
made in connection with deep ditching, cutting the bottom to an exact grade, or cutting curves;
longer moves are feasible for rough, shallow work.
Curves. Curves are dug as a succession of short, straight ditches, but a skilled operator can
bevel the edges to produce a smooth curve. The machine stands with its center a little outside of
the centerline, and digging is done in the outer half of the bucket reach. Moves are short.
Angles. Many kinds of pipe require laying in straight lines and angles rather than curves, and
trenches in which they are to be placed are dug accordingly. Angles are made by digging slightly
past the angle point, then shifting the shovel to straddle the new centerline, as in (B).
Spoil Piles. Spoil from the ditch is usually piled on one side, far enough back to allow a foot-
path or working space between it and the ditch. If a large volume of dirt is being moved, the pile

P

A

BOTTOM GRADE
B
FIGURE 5.2 Separating topsoil.