10---Thursday---Outbursts Flashcards
What are the Main outburst Conditions indicators at a mine list 5?
WARNING SIGNS
Conical cavity in the face or ribs
Mylonite or crushed coal thicker than 500 mm
Any sign of abnormal stone in the face, fault dyke, white calcite.
Abnormal geological features, slickensides
A change in frequency or orientation of joints in the coal
Coal spitting from the face during mining
Coal face bulging
Increased face noises
Abnormal red/brown dust on roof or ribs
Gas or water hissing from face under pressure
Resin ejected from rib dowel holes
All these sign could represent a change from the normal situation
CHANGE IS THE MAIN WARNING SIGN FOR POSSIBLE HAZARDS AHEAD
WHAT TO DO IN THE EVENT THAT AN OUTBURST DOES OCCUR.
Make your way to the nearest fresh air location (intake airway, cribroom).
If you are in the immediate face area you MUST immediately don your oxygen self rescuer.
Do not remove your oxygen self rescuer until you know that the atmosphere is free of contaminants (oxygen deficiency or carbon dioxide).
If possible keep the ventilation fan running
Notify the ERZ Controller as soon as possible
Conduct a head count to establish that all of the crew are accounted for.
The ERZ Controller to notify the Shift Undermanager
DO NOT attempt any rescue unless you are competent and confident in the use of the specialised rescue equipment (generally Compressed Air Breathing Apparatus – CABA
WHAT IS AN OUTBURST?
An outburst is a sudden release of coal and gas under pressure from a working face area.”
As the mining process approaches an outburst prone zone, the barrier between the approaching face and the zone is reduced until such time as the pressure becomes too great and invades the cavity created by the mining. Generally outbursts invade the face area from in front of the mining but, have been known to originate from the rib (side) of a development panel face area.
Outbursts have occurred along the face of an operating retreat longwall.
list some of the features of a gas outburst
The violence associated with the outburst is proportional to the gas pressure
gas content
gas composition.
A significant increase in the gas released from the face area.
Outbursts generally occur over a period of several seconds.
A cone shaped cavity is a usual remnant following an outburst.
Outbursts are related to localised stresses within the seam.
The energy released is proportional to the gas pressure, the gas content and the gas composition in or behind the structure
There are four main features associated with outbursts. What are they?
CONDITIONS ASSOCIATED WITH OUTBURSTS
1.HIGHER THAN NORMAL SEAM GAS
higher than normal seam gas usually results in higher gas pressure and thus higher gas concentrations at the working face.
2.GEOLOGICAL STRUCTURES
these may include intense jointing, mylonite zones, fault zones, strike slip faults, cutters through the roof, changes in the angle of cleat.
3.STRESS
increase or changes in the localised stresses in the strata.
4.COAL STRENGTH
the more cleats and bedding planes, the weaker the coal. weak coal may be ejected by higher gas pressure more easily than strong coal.
