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Gas Bag

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

gas bag

Entry link: Gas Bag


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.

Entry link: Geophone

Geotechnical failure modes

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

These are:

Entry link: Geotechnical failure modes


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

Entry link: Geothermal


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

Entry link: gm/m

grains per 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.

Entry link: grains per foot

Ground Vibration

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.





Entry link: Ground Vibration