Page 429 - Moving the Earth_ The Workbook of Excavation

BLASTING AND TUNNELING

BLASTING AND TUNNELING 9.29

Portable magazines to hold a few cases of powder or boxes of caps are most easily made from
large metal tool or packing boxes fastened with padlocks. When properly marked these are legal
in most states, although many laws and regulations recommend more complicated units. When a
portable magazine is to be left on a job, it should be chained and locked to a tree or other anchor.

Handling. Dynamite may cause severe headaches. This is especially apt to occur if it is unwrapped
and handled with bare hands. Different brands and strengths differ in headache-producing qualities,
and individual reaction is highly variable.
Persons handling explosives should not smoke and preferably should not carry matches. A com-
plete list of safety precautions recommended by the manufacturers will be found in each box of dynamite.
A complete list of the “don’ts” issued by the Institute of Makers of Explosives is included in the Appendix.
Boxes. Dynamite is usually packed in 50- or 60-pound boxes, although 25 pounds may be available.
The wooden box, which was inseparable from blasting operations for many years, is no longer used.
The standard box is now made of fiberboard, with a full lift-up cover whose overlap provides
double sides for the container. Sealing is by means of tape.
The box is lined by a polyethylene bag, which is an effective moisture and chemical barrier,
and can be readily opened and reclosed in the field.
A small possibility of damage to both the dynamite and the liner, with resultant contamination
of the fiberboard with explosive, is the reason that these boxes should not be burned, except with
the same precautions as with dynamite itself.

LOADING

Holes may be loaded in a number of ways. These may be classified as solid, string, spaced, deck,
and spring.

Solid. In solid loading as much explosive is crammed into the hole as possible. Free-running
explosive is poured into the hole, or blown in pneumatically from bulk carriers or from portable
hoppers. The air tends to build up static electricity, so the unit must be grounded, and other pre-
cautions taken. (See Fig. 9.23.)
Water gels are usually loaded in their plastic containers, which may be intact or slit, but may
be poured in. On large-scale operations it is economical to use a truck pumper, which may mix
the ingredients also.

FIGURE 9.23 Grounding a loading hopper. Note: Mounted Du Pont Airloaders should be
grounded to the ground with cable or wire. DO NOT use chain.