A two-conductor cable used for completing the circuit between the electric
blasting cap (or caps) and the blasting unit or other source of electric
energy. Syn:blasting cord
A pair of insulated copper conductors which lead from the exploder to the
detonator wires. It may be either twin-core (both conductors contained in
the one cable) or single-core (each conductor contained in a separate
cable). Twin-core cables having cores of four strands, each 0.018 in
(0.046 cm) in diameter (4/0.018) with a resistance of approx. 5 Omega per
100 yd (91 m), are commonly used. Actual choice of cable must depend upon
conditions of use and the relevant regulations.
Syn:twin-core shot-firing cable
The methods of testing twin-core and single-core cables are identical. Two
tests are applied, one for insulation and one for continuity, and where
large and important charges are being fired, as in tunnel, wellhole, and
quarry blasts, tests are made before every blast. For the cable insulation
test, an approved circuit tester or ohmeter is connected to one end of the
cable, the two conductors at the other end being separated. No current
should flow, and the resistance should be infinite. For the continuity
test, the two far ends of the cable should be joined. The tester should
show that the current is complete, or if an ohmeter is used, this should
show the correct resistance of the shot-firing cable. Nelson
Extends from the exploder along the shot-firing cable, detonator wires,
and finally the detonator. The shot-firing circuit is the path taken by
the electric current from the exploder when a shot is detonated.
Nelson
A steel chain mat suspended from the roof about 9 to 12 ft (2.74 to 3.66
m) from the face of an advancing tunnel to limit damage to equipment and
danger from flying debris when shot firing at the face. It consists of a
steel frame with chains suspended about 6 in (15 cm) apart.
See also:blasting curtain
The firing of a number of shots in a tunnel, or shaft sinking at one
operation with instantaneous or delay detonators. Nelson
See:blasting unit
a. A hole drilled for the purpose of shot firing. BS, 12
b. A hole drilled in coal, ore, or rock, usually from 3 to 9 ft (0.9 to
2.7 m) in length (underground), for breaking down the material by means of
explosives. Nelson
c. The borehole in which an explosive is placed for blasting.
See also:blasthole
d. See:shot point
e. A borehole drilled with a shot drill. Long
f. In seismic prospecting, a borehole in which an explosive is placed for
generating seismic waves. AGI
a. When an obstruction in the shothole makes it difficult or impossible to
get the charge deeper, the hole is said to be bridged. A narrow diameter
in the hole due to a resistant bed often makes it difficult to get the
charge down the hole. A mechanical device that purposely bridges the hole
at a shallow depth in order that the hole may be filled. AGI
b. An obstruction in a shothole that prevents an explosive charge from
going deeper. It may be accidental or intentional. AGI
Lightweight pipe, usually about 4 in (10 cm) in diameter. A typical joint
of casing is 10 ft (3 m) long and has threaded connections on both ends.
The primary use of casing is to prevent the shothole from caving and
bridging. The lightweight casing may be considered as an expendable item.
AGI
a. Generally, a rotary percussion or auger type drill for making shotholes
for blasting.
b. Drills for shotholes are of two general types: (1) the rotary drill and
(2) the churn drill. Rotary drill methods can be subdivided into (1)
mechanical feed and (2) hydraulic feed. Both types provide a means for
rotating the pipe, and both make provisions for circulating fluid down
through the pipe, thus washing the cuttings away from the bit and
conveying them up to the surface in the annular space between the wall of
the hole and the string of drill pipe. The churn drill is similar to the
larger cable-tool type. It is seldom used except in areas where
underground cavities hamper the return flow of the circulating fluid used
in the rotary methods. Portable drills, water jets, and airblast equipment
and augers are also used in certain areas. Syn:blasthole drill
AGI
The elevation of the ground at the top of the shothole. AGI
Phenomenon causing observed travel times to a fixed receiver point to
increase with successive shots in the same hole. AGI
The drillers' record of the depths, thicknesses, and lithologic
characteristics of the formations encountered in the seismic shothole.
AGI
A plug, usually of wood, used by seismic field parties to plug a hole upon
completion of shooting. This prevents caving, protects the public from
injury, and protects the exploration company from damage claims that might
result from open holes. AGI
The elevation of the explosive charge in the shot hole. Not to be confused
with shothole elevation. Syn:shot break; time break; shot moment.
AGI
Metal in the form of small, spherical, or nearly spherical, pellets. It is
usually made by causing molten metal to fall, dropwise, from a suitable
height into a quenching medium. Also called shot. Henderson
See:time break; shot instant.
An electric line wrapped around a dynamite charge and connected to a
telephone or radio circuit. The explosion breaks the circuit to record the
shot instant or moment. Use is largely obsolete. AGI
A method of breaking coal from the solid seam by the use of explosives,
when the seam has not previously been cut or sheared to prepare the coal
for blasting. Also called shot fast. BCI
The point at which a charge of dynamite is exploded for the generation of
seismic energy. In field practice, the shot point includes the hole and
its immediately surrounding area. See also:shothole