Page 173 - Moving the Earth_ The Workbook of Excavation

BASEMENTS

BASEMENTS 4.13

that has a torque converter. If the wall is high, the machine must be moved forward again after the
bucket lip gets above the push arm hinges.
This back-and-forth motion compensates for the curved path of the rising bucket. The same
effect may be achieved by careful regulation of the bucket tilt, as it makes a shallower cut when
rolled back than when flat.
Any jogs or irregularities can be cut by digging into the wall from the excavation without mak-
ing additional ramps. It is easiest to take these out in layers as the floor of the hole is worked
down, but they can also be dug after completion of the main work.
Soil carried out of the hole may be spread or distributed to nearby low spots much more easily
than by a dozer, and can also be readily loaded into trucks.
Crawler loaders are usually preferred for basement work, but it is done by four-wheel-drive
machines also.

Digging under Buildings. A special feature of most small front-end loaders is their ability to
dig basements under existing buildings. Particular attention must be paid to bracing the structure
over the hole through which entrance is effected, and across any interior pillars which are to be
moved. Digging should be done cautiously to avoid damaging the building through collision with
rocks, beams, or soil pipes in direct contact with it.
If the building is not large enough that the machine can dig a turning place inside it, it will be
necessary to use hand labor to cut back to some of the walls.
Ventilation is very important, and usually requires at least the use of a powerful electric fan to
keep the air reasonably free of exhaust fumes.
A machine that is to do much work indoors must be diesel, with a scrubber (fume reducer) on
the exhaust.
Hydraulic shovels equipped with telescopic booms can dig under a building from outside,
either directly or by removing hand-dug dirt.

BACKHOE EXCAVATOR

The backhoe is a principal competitor for small basement work. There are two types: full-revolving
hydraulic or tractor-mounted part-swing hydraulic. Tractor mountings get into difficulties because
of restricted swing, and often limited reach. But they can dig a basement efficiently.
Any hoe is capable of shallow digging, but compares most favorably with the dozers when the hole
is to be over 6 feet deep, or when unfavorable bottom conditions, such as water, mud, boulders, or
ledge, are encountered. It is able to take care of any necessary ditching without change of attachments.
It is recommended that the digging lines be set a few inches outside of the required excava-
tion, although in even-textured soil the backhoe can do a very exact job. In addition to the corner
stakes, intermediate guide pegs should be set at short intervals along the digging lines, as the oper-
ator cannot sight along these lines without getting down from the shovel, and the finished wall is
established with the first cut.
Figure 4.13 shows the 20 by 30 basement with the depth increased to 8 feet.

Lining Up. Accurate lining up of the machine is essential for a clean job. If the cut is to begin
along the south line, the shovel is placed as in (A), with the bucket about three-quarters extended
and resting a few inches beyond the southwest corner. The boom and the tracks are parallel with
the south digging line. Lining it up in this manner is greatly simplified by marking the width of
the bucket (including side cutters, if used), centered, on the bottom of both dead axles, with paint,
or better yet, with stubs of welding rod. Sighting across the outside pair of these marks from the
rear, the outer edge of the bucket should be exactly in line with them, and all three points should
be on the digging line.

Digging. A ditch is now dug to bottom grade with its left edge on the digging line, and the spoil is
dumped to the south. The far end of the ditch will curve rather sharply inward. When the backhoe