Blast Training International

An inflatable bladder used to block off a blast hole and support explosives or stemming.

A geophone is a device that converts ground movement (velocity) into voltage.

Geophones typically comprise a spring-mounted magnetic mass moving within a wire coil to generate an electrical signal. The response of a coil/magnet geophone is proportional to ground velocity.

Geophones for recording blasting vibration should be able to record from 0.1mm/sec to 300mm/sec and over a frequency range from 4.5 Hz to 250 Hz.

Geophones require annual calibration by an approved testing station (NATA) to ensure they continue to accurately record ground vibration.

There are a number of common failure modes relating to rock slope stability.

These are:

• Plane failure
• Wedge failure
• Rock fall failure
• Rock topple failure
• Rotational failure
• Block slide failure

Pertaining to heat energy extracted from reservoirs in the earth’s interior.

Grams per metre. Common expression of core loading of detonating cords. (1 gm/m = 4.7 grains/foot).

Grains per foot is a measure of the explosives loading in detonating cord. The term is in imperial units and cord from North America is often rated in these units.

A grain is a unit of weight with 1 gram = 15.43 grains.

The conversion from grams per meter to grains per foot is:

1 gram per meter = 4.7 grains per foot.

Oscillatory movement of the ground caused by the passage of seismic waves.

Ground vibration is typically measured as a velocity of ground motion in millimeters per second using a seismograph.

A seismograph consists of a data recorder connected to a geophone. Geophones are devices that convert ground movement into voltage using a moving magnet and coil arrangement.