Page 529 - Moving the Earth_ The Workbook of Excavation

PIT OPERATION

PIT OPERATION 10.35

FIGURE 10.25 Benching from the top and bottom.

the same manner as topsoil, but it is usually more convenient to dig directly, with carrying scrapers
or cable excavators.
Rooters may be used to loosen the ground for scrapers and for cable excavators except in wet
digging.
The wheeled scraper is more flexible in digging, can vary the dumping spot readily, and by
change of the number and size of the machines can excavate at almost any rate desired. The
machine may also be used in other pit work or outside jobs when the cut is idle.
Under favorable conditions, the cable excavator can dig at lower cost per yard. The fact that it
is difficult to move is sometimes in its favor, as it will be there when needed.

SURFACE WATER

Rain. Rain will usually stop excavating and hauling operations. In addition, it may soften stock-
piles and turn pit floors and haul roads into swamps or ponds so that work may not be resumed
for days or weeks.
Some pits are in such porous soil that any volume of water will soak away quickly, and neither
mud nor standing water will delay work more than a few hours. Others are in such dry climates
that it is better to run a small risk of water delay than to spend the necessary thought, time, and
money on arranging for drainage. The majority, however, are so situated that at least routine pre-
cautions should be taken to keep them usable.
A first principle is to shape pit floors so that they will drain. In cutting into a hill, the floor should
slope slightly upward toward the face so that water will flow away from this line of greatest activity.