Expansion energy of coal gas for the initiation of coal and gas outbursts

In deep mine, coal is usually subjected to coupled high gas pressure and static compressive stress. The coal may be also subjected to dynamic loading due to the sudden fracture of hard roof during mining. In our previous study, the behaviour of gas-containing coals with initial gas pressure was investigated subjected to uniaxial static compression. In this study, the dynamic compressive behaviour of gas-containing coals with gas pressure and static axial preloading is investigated using a modified Split Hopkinson Pressure Bar (SHPB) system. The dynamic behaviours of gas-containing coals under SHPB tests are studied by varying initial gas pressure and axial static preloading. The testing results include strain measurements and energy dissipation. In addition, the wave impedance method is used to quantify damage of gas-containing coals under coupled gas-static-dynamic load. It is found that the dynamic compressive strength of gas-containing coal under coupled load decreases with the increasing initial gas pressure. The gas-containing coal with higher gas pressure and axial static preloading is more vulnerable to dynamic loading. The findings can be applied to mining design or support design in deep mining of high-gas-containing coal seam.

Dynamic Compressive Test of Gas-Containing Coal Using a Modified Split Hopkinson Pressure Bar System

Influence of coal moisture on initial gas desorption and gas-release energy characteristics

Simulation of the hazard arising from the coupling of gas explosions and spontaneously combustible coal due to the gas drainage of a gob

Investigation of the discharge law for drill cuttings used for coal outburst prediction based on different borehole diameters under various side stresses

Experimental research into the relationship between initial gas release and coal-gas outbursts

A method of rapid determination of gas pressure in a coal seam based on the advantages of gas spherical flow field

In the process of working face advance in longwall coal mining, a great deal of gas relieved by the strata adjacent to the mining coal seam and the residual coal in gob migrates to gob. If the gas drainage method in gob is unreasonable, gas will accumulate in the upper corner and overrun in the return air flow. In the paper, a CFD (computational fluid mechanics) model of gob based on the actual geological conditions and gas drainage mode of 1262 working face of Dingji Coal Mine, China, was established. The gas drainage modes that should be taken to effectively control gas accumulation in the upper corner and gas overrun in the return air flow at different gas emission rates were discussed. The simulation results show that when the gas emission rate in the working face is lower than 20 m3/min, buried pipe drainage can effectively control gas accumulation in the upper corner and gas overrun in the return air flow. When gas emission rate there is between 20 and 30 m3/min, the two problems can be solved through cross-measure borehole drainage combined with buried pipe drainage. When gas emission rate there is higher than 40 m3/min, they can be effectively controlled through a three-dimensional drainage mode including buried pipes, cross-measure boreholes, and surface wells. Arranging surface wells within the fractured zone near the return airway can increase the gas drainage rate, and the gas concentration can reach over 85%; the gas concentrations of buried pipe drainage and cross-measure borehole drainage are 15~20% and 70~80%, respectively.

Design of gas drainage modes based on gas emission rate in a gob: a simulation study

The invention discloses a quick pressure-relief gas discharge method for exposing a super-thick and soft outburst coal seam in a vertical wellbore. The method comprises the following steps: designing discharge drilling holes in several circles along the contour of the wellbore heading face; dividing the drilling holes into a plurality of nine-hole thrusting units, and nine-hole injection units; drilling for each nine-hole thrusting unit and each nine-hole injection unit; conducting pressure test for drilling; thrusting coal of the 9 holes of the nine-hole thrusting units and the nine-hole thrusting units sequentially; constructing a gas inspection hole in the area of the nine-hole thrusting and nine-hole injection units in the thrusting, and measuring gas content; cementing the 9 drill holes of the nine-hole thrusting units and the nine-hole injection units after measuring the gas content; thrusting and cementing all the nine-hole thrusting units and the nine-hole injection units sequentially. The quick pressure-relief gas discharge method avoids the problem of cracking of the borehole wall after the change of the punching stress, and strengthens the coal, and increases the single hole discharge under the premise of ensuring the safety, and realizes the quick pressure-relief gas discharge of the super-thick and soft outburst coal seam.

Quick pressure-relief gas discharge method for exposing super-thick and soft outburst coal seam in vertical wellbore

The invention discloses a segmental drilling flow method and device for predicting the outburst danger of a coal roadway, and belongs to methods and devices for predicting the outburst danger of coal roadways. The device is composed of a twisted drill rod, a hole sealing device, a dual-cone filtering drum, a guiding device, a flow pipe, a low-rate sensor, a high-rate sensor, a coal dust hopper, a coal dust discharge pipe, an intrinsic safety type data acquisition processor, a hand pump and an electric coal drill. According to the device, a tablet computer and the sensor technology are combined, the outburst danger of each coal body is predicted by measuring the gas emission quantity of a drilled hole section by section in the drilling process of the coal roadway; and the intrinsic safety type data acquisition processor and a battery are adopted to supply power, and the method and lightweight device for predicting the outburst danger of the coal roadway are achieved. The device is light in structure, easy to use, accurate and reliable in testing, and capable of directly judging whether dangers exist in front of a working plane of the coal roadway or not, where the coal bodies with the outburst danger and how far tunneling can be conducted safely.

Wang Chaojie

Papers

Experimental research into the relationship between initial gas release and coal-gas outbursts

A method of rapid determination of gas pressure in a coal seam based on the advantages of gas spherical flow field

Design of gas drainage modes based on gas emission rate in a gob: a simulation study

Quick pressure-relief gas discharge method for exposing super-thick and soft outburst coal seam in vertical wellbore

Segmental drilling flow method and device for predicting outburst danger of coal roadway