Study On Technology Of Continuous Flow About Outburst Hazard Prediction During Driving In Soft Coal Roadway

There are lots of soft-coal seams in the outburst coal. For the soft-coal has low hardness, high speed of gas scattering, poor permeability, the outburst risk of coal seams becomes higher and it threats the workers'safety seriously, meanwhile, outburst prevention workload greatly increasing, excavating speed greatly slower, leading to the mining imbalance during driving in the coal tunnel. The conventional outburst forecast on coal roadway is point prediction and it has many defects. Based on the existing problems of outburst prediction and characteristics on the coal roadway at home and abroad, the continuous flow method is used to liner forecast the outburst risk of soft-coal. This is a kind of'liner' prediction technology.According to the view of the Soviet Union scientistsИ.В.Павлов, there is no coal and gas outburst risk when excavations in the pressure relief zone. If the pressure relief zone is short, but excavating velocity is too fast, it's easy to expose the coal in the concentrated stress zone, and the high-pressure gas desorbs fast, forming high gas pressure gradient, which likely cause outburst. Based on Professor Jiang Chenglin's theory:the principle of the "spherical shell stability losing" mechanism and the initial releasing gas expansion energy, The technology of continuous flow used to outburst forecast was proposed. Through continuous real-time recording gas flow desorbs from drilling, the scope of pressure relief zone, the regional distribution of outburst coal are determined.The several outburst phenomenon and its causes are analyzed during driving in coal roadway. The physical characteristics, damage type, adsorption of soft coal are detailed studied. The reasons is analyzed that the outburst danger of the pressure relief zone is low in soft coal, while the concentration and original stress zone is high.The mechanical model of spherical coordinates that coal body before the excavation workface is established and its balance equation is derived, and the tangential and radial stress solution and the plastic zone radius are solved. Conclusions are obtained by numerical:the elastic-plastic region radius increases along with the excavation depth increases, but increases along with the cohesive force and the angle of internal friction reduces. Stress field is simulated using FLAC3D, The coal body biggest principal stress, the elastic-plasticity radius and the coal bed inclination angle change relations, elastic-plasticity radius and elasticity coefficient relations are analyzed. The gas emission law from drilling is summarized; That the gas's radial flow model around the coal drilling, spherical flow model of coal around the driving workface and gas flow model from the drilling cuttings were established, and flow equations were deduced, its analytical solution were solved; That the gas emission law in the borehole in case of the steady-state and unsteady flow were analyzed through numerical calculation; That the litter gas emission laws were simulated with the empirical equations.The use, the principle and operation process of every components of continuous flow method prediction device were analysised. A method was put forward that sealing gas with coal duff as dynamic and open type, using the manner that plusing coal duff to increase the resistance of gas flow at the clinder'exit, and forcing the gas gush from drill flow out of gas flow sensor where the resistance is less during the drilling with twist drilles. It can guarantee directly use the twist drilles to drill in coal seam, and regardless sealing the twist drilles in a colsed space.The calibration scheme of Flow Velocity Sensor and Displacement Sensor were made. By a series of experiments, the electric current and gas flux linear curve of Flow Velocity Sensor, as well as the electric current and displacement linear curve of Displacement Sensor were fit.The principle of plugging gas with dynamic open coal duff and the gas leakage reason were analyzed. Through a series of leakage experiments show that the air leakage rate decreases with increasing air volume. It shows that the method is reliable.Continuous flow forecast equipment was used in theNo.II-1 soft-coal seam 11071 wind roadway of LiangBei coal mine.Through analyzing the gas flow curve, coal roadway outburst prediction indicator with continuous flow method was studied. A kind of the concept of flow-area was put forward, and then the outburst dangerous of coal roadway was judged through the flow-area and the distance from the center to its working face. The larger of the area of gas flow, and the shorter of the center distance from working face, then the greater of the outburst dangerous of coal roadway working place.In addition, compare to forecasting results of continuous flow method and traditional indexes of coal roadway outburst prediction, in the corresponding forecasting period determining drillings volume,desorption index of drill-cuttings, and observing whether there is any gas dynamic phenomenon in each circulating footage in the mining process,and then using the acquisition of the line predictor to judge whether there is outburst dangerous. At present,secure value of flow method has been given while the working face do not occur coal and gas outburst,With the accumulation of field data, the critical value will be gotten when coal and gas outburst occurs in the coal roadway.There are 94 pictures and 19 tables and 116 references.