摘要
Underground coal mining activities in the Quangninh coal basin (in the North ofVietnam) have been carried out at a depth of-130 m to-150 m,and in the near future thismining depth will become-300 m and-500 m.Together with the increasing coal output,the quantity of methane and other mine gases emitted from coal beds during mining activitieswill grow bigger and bigger.According to the forecast of the coal mining industry,ifmines go deeper downward,all underground coal mines in the Quangninh basin will beclassified into the mine group with the dangerous level of methane bearings.Mine gascontrol and management operations with conventional ventilation are less effective andentail high expenses.One of the main solutions is to carry out short,medium and longboreholes for controlling and recovering methane and other mine gases from coal bedsbefore mining activities.Efficiency of drilling activities for methane gas recovery from coalseams with horizontal bore holes at underground coal mines depends on many factors includingthe mine gas draining borehole layout at the roadways,gas content in the coalbeds,technologies for mine gas draining boring activities,and so on.Methane gas existsin the coal beds under the adhesive state with stable physical and chemical bonds.In orderto recover these gases,it is necessary to carry out boreholes and create artificial joints(collecting pits) in coal beds with the impulse method (hydraulic separation method).
Underground coal mining activities in the Quangninh coal basin （in the North of Vietnam） have been carried out at a depth of-130 m to -150 m, and in the near future this mining depth will become -300 m and -500 m. Together with the increasing coal output, the quantity of methane and other mine gases emitted from coal beds during mining activities will grow bigger and bigger. According to the forecast of the coal mining industry, if mines go deeper downward, all underground coal mines in the Quangninh basin will be classified into the mine group with the dangerous level of methane bearings. Mine gas control and management operations with conventional ventilation are less effective and entail high expenses. One of the main solutions is to carry out short, medium and long boreholes for controlling and recovering methane and other mine gases from coal beds before mining activities. Efficiency of drilling activities for methane gas recovery from coal seams with horizontal bore holes at underground coal mines depends on many factors in- cluding the mine gas draining borehole layout at the roadways, gas content in the coal beds, technologies for mine gas draining boring activities, and so on. Methane gas exists in the coal beds under the adhesive state with stable physical and chemical bonds. In order to recover these gases, it is necessary to carry out boreholes and create artificial joints （collecting pits） in coal beds with the impulse method （hydraulic separation method）.
