Page 200 - Moving the Earth_ The Workbook of Excavation

DITCHING AND DEWATERING

5.2 THE WORK

in many sizes, ranging from compact, self-contained systems, mounted on skids or trailers, to
larger truck-mounted models.

DITCHING WITH A BACKHOE

Types. There are two types of backhoe used in ditching. We have the full-revolving hydraulic
hoe, with crawler- or wheel-mounted undercarriages. And there are smaller hydraulic hoes car-
ried on the backs of tractors (or rarely, trucks), whose arc of swing is 200° or less.
Design and operation of these various machines are discussed in Chap. 13.
The hydraulic models provide complete control of most bucket motions, with power for up and
down, and pull and push. A “wrist action” bucket can be adjusted in angle during the digging pass
for precise control of cutting, for tremendous breakout force on obstructions, for nonspill carry-
ing of bucket loads to the dumping point, and for selection of place and rate of dumping.
Some crawler-mounted hydraulics have separate speed and direction control of the two tracks,
a refinement that helps maneuvering in restricted space and reduces cutting up of the ground.

Width. Ditching with any machine is easiest and neatest if the trench is the same width as the
bucket cut. This width is that of the bucket itself, plus any side cutters it may carry. The bucket should
be wider at the front than the back, to prevent the sides from binding in the cut and to simplify
dumping.
Standard bucket widths, with or without side cutters, are 18 to 42 inches. Small machines may
be as narrow as 12 inches, and big ones 5 feet wide or more.

Direction of Work. A hoe should start at, and dig away from, any obstacle it cannot cross, such
as a building. If there are two such obstacles, separate starts are made at each, and an extra-work
connection is made between the two trenches.
If the centerline is on a grade, working in the uphill direction makes digging more difficult, by
reducing digging force and increasing the tendency of the bucket to pull the machine into the ditch.

FIGURE 5.1 Lining up a hoe.