FUNDAMENTALS

LONGWALL MINING

ROADWAY DEVELOPMENT

OUTBURST

• overview
  • definitions
    • outburst size
    • outburst cavern
  • gallery
  • about the outburst site
  
  
• factors
  • mining
    • depth of mining
    • mining induced stresses
    • faults and folds
    • seam thickness
  • gas
    • gas environment
    • gas content
  • coal
    • strength of the coal seam
    • rank of coal seam
    • permeability
    • volumetric change
    • cleats and joints
  
  
• management
  • prediction
    • geology
    • prediction indices
    • monitoring
    • geophysical
    • gas environment
    • gas content
  • prevention
    • gas threshold limits
    • gas drainage
  • control
    • ground destressing
    • gas drainage
    • hydraulic fracturing
    • pulse infusion shotfiring
    • water infusion
    • outburst management plan
  
  
• research & publication
  • ACARP Reports
  • Presentations
  • Publications Australia
  • Publications International
  • References
  
  

	factors
		gas
			gas content

Methods of estimation of gas content of coal seams (Lama and Bartosiewicz, 1982)

Method	Requirement	Method of Interpretation	Accuracy	Country	Method of Measurement	Applicability	Reference
Direct	Cores	Requires knowledge of gas emission laws	Depending upon time lost, core quality and applicability of gas emission laws. ±50%- ±20%	UK, USA, Australia	Volumetric gas emission atmospheric pressure followed by crushing	Good from surface boreholes and doubtful from underground boreholes, fractured cores etc. Degree of fracturing influences results	Graham, (1937), Bertard, et al, (1970). Belin, (1971)
Direct	Sampling of fractions	Empirical	?	Poland	Volumetric gas emission	Existing mines	Ettinger (1958)
Indirect (statistical)	Lumps of coal	Statistical analysis of gas content of lumps	± 20%, statistically measured values from face samples are consistently higher	UK	Sample (30 - 40 mm size), collection at the face and estimation of gas contents.	For seams under mining, face sampling, applicability to highly variable and high rank coals not proved
Indirect (adsorption isotherms)	Pressure measurement and sampling	Direct readings for adsorption isotherms	Depending upon pressure measurements and sampling (~10-20%)	Poland Russia, Australia, Germany	Volumetric techniques and gravimetric techniques	For seams under mining and seams lying above or below	Lama and Bartosiewicz, (1982) Aziz and Ming Li (1999)
Indirect	Proximate analysis of coal	Empirical	~30-100%	Russia, USA Poland	Chemical analysis	New and existing mines	Ettinger, (1958), Kim (1977)
Indirect	Exhaust ventilation sampling	Subtraction techniques	± 20%	Australia	CH4 or CO2 gas analysis (%)	Existing mines	Lama, (1980) Tarnowski (1972)
Indirect	Sampling of exhaust mine air	Empirical	± 50%	Germany, USA	Volumetric gas emission	Existing mines- general make of gas	Noak, (1976)