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The Effect Evaluation of Removing Outburst Through Bedding Drilling and Borehole Combined Gas DrainageZHAO Zhong-ming WANG Lei(School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China)Abstract: In order to test the validity of prevention of outburst in 3104 coalface where takes measures of the bedding drilling and Borehole combined gas drainage, according to the relevant provisions, use Drilling index, Pre pumping index and Gas index to evaluate the effect of removing outburst in 3104 coalface. The evaluation results show that through the preliminary drainage of gas, the coalface has eliminated the danger of outburst and created favorable conditions for safety mining.Key word: removing outburst; evaluate; drilling indicators; gas pre-pumping rate0 IntroductionIn order to ensure the safe production of the outburst, in the prominent seam implement the measures of outburst prevention later, test the effect of outburst prevention measures to eliminate the outstanding requirements, to Regional measures eliminate prominent evaluation research is very necessaryReferences1 Nie Hongguo. Evaluation of The Coalface Removing Outburst MeasuresJ. Safety In Coal Mine, 2011(1):127-129(in Chinese)1.1 About coalface3104 coalface is located in the three-level of nine mine of Hebi ,the mining area is 6.58104m2. The coalface south to rail transport Lane of the northern -420m level, east to 3102 coalface, west to protection pillar of the new air shaft, north to the unexplored area; The seam floor elevation of -410 -515m, and the corresponding ground elevation between +195 +222m. The coalface was arranged to tilt, from Open-off cut to Stop Line is 548m, the average length of the coal face is 120m, and the average angle is 10 , mining height is 8.0m. Reserves of coal is 736,500 tons. According to the determination of Safety Engineering Research Center of Henan Polytechnic University, the original gas content of 3104 coalface is 20.60m3/t, the gas pressure is 0.98Mpa. The gas content and pressure has exceeded critical value of the coal and gas outburst, therefore, the 3104 coalface has coal and gas outburst dangerous.Fig 1 3104 coalface layout2 Measures of coalface Removing Outburst3104 coalface used the Bedding drilling and Borehole prevention of coal and gas outburst. Eliminate outburst principle is a by drainage certain amount of gas, resulting in gas potential and flexibility in coal can be released, so that the seam pressure has been released, coal weakening or eliminating highlight the power to increase the prominent resistance, thereby weakening or even eliminate prominent dangerous2 Zhang Jingli. Study on Outburst Elimination Test of Coal Mining Face with Outburst Danger in PotentialJ. Coal Science and Technology, 2009(3): 38-40(in Chinese)2. The drilling layout parameters: drilling diameter 94mm, hole spacing 1.5m, hole depth of 70m, the sealing length 9m, Aner sealing technology. Drilling works are shown in Table 1. Table 1 Drilling works of 3104 coalfaceLocations of constructionDrilling quantities/aDrilling engineering/mRemark3104 coalface1861136265the Bedding drilling3104 backplane Drainage Roadway195898872BoreholeTotal38192351373 Evaluation of coalface Removing OutburstAccording to the relevant laws and regulations of the pre-pumping coal seam gas,the following indicators can be used in evaluation of coalface Removing Outburst:1 drilling indicatorsDrainage hole should control the entire pre-pumping area ,and uniform layout3 State Administration of Work Safety, State Administration of Coal Mine Safty. Prevention of Coal and Gas Outburst RequirementsS. Bei Jing: China Coal Industry Publishing House, 20093. No blank tape of the strike, dip and thickness along the coalface.2 Predrainaging indicatorsPre-pumping rate of Seam gas should be more than 30%4 State Administration of Work Safety, State Administration of Coal Mine Safty. Mine Safety regulationsS. Bei Jing: China Coal Industry Publishing House , 20114.3 Gas indicatorsAfter gas drainage of Stope, the gas content of coal should be reduced to less than 8m3 / t, or the gas pressure of coal seam should be reduced to less than 0.74MPa5 State Administration of Work Safety, State Administration of Coal Mine Safty. (AQ1026-2006)Basic Index of Coal Mine Gas Drainage and ExploitionS. Bei Jing: China Coal Industry Publishing House , 20075 .Meanwhile, analysis the reasonableness of the Cell division, the representativeness of the measuring point and the normative of measures of Gas indicators.3.1 Residual gas contentUsing cuttings desorption method for the determination of the gas content. The principle of the method for the determination of the gas content is: first, using the desorption method for the determination of the amount of gas desorption of coal samples; Then based on the amount of gas desorption of coal samples, desorption law calculate the lose gas content; Again combined residual gas content in the coal sample to calculate the total gas content in the coal samples. According to the relevant provisions, and combined with the actual situation of the mine, determination of the gas content were arranged 14 holes. The drilling layout shown in Figure 2. According to the field measured data and laboratory analysis, gas content measurement results are shown in Table 2.Fig 2 Drilling layout of 3104 coalfaceTable 2 The gas content of determination in 3104 coal faceHole IDNatural gas composition（%）Desorption gas content（m3/t）Loss of gas content（m3/t）Residual gas content（m3/t）Total（m3/t）1# 76.080.820.431.843.092# 75.670.780.361.933.073# 74.520.420.113.874.404# 62.810.580.242.463.285# 77.690.260.124.454.836#78.830.210.104.494.807# 78.460.230.144.705.078# 70.590.830.242.473.549# 69.870.780.261.822.8610# 65.180.930.481.112.5211# 59.640.850.361.642.8512# 27.000.830.411.702.9413#70.720.790.381.462.6314# 70.020.810.331.923.063.2 The residual gas pressureThe measured using a direct method of measuring residual gas pressure. Residual gas pressure measured by drilling in a suitable rock lane. In order to ensure the reliability of pressure measurement, select the measurement locations principles:Locations should be selected in Shimen or rock lane, with no faults, fissures and other geological formations. And the status of its gas occurrence to have a representative.The manometry drilling should avoid the aquifer, cave, and shall ensure that the manometry drilling to its distance not less than 50m.The test sites of the pillar should be denser, and from the coal seam vertical thickness of not less than 10m.Drilling see the coal-point and Shimen see the coal-point of the straight line distance should not be less than 20m. And same position of two drilling see coal-point of the straight line distance should not be less than 20m.According to the coal seam, the roadway layout and other conditions, the pressure measurement are selected in the two areas. These two regions are East return airway and 3104 backplane Drainage Roadway. East return airway construction of six boreholes, the 3104 backplane Drainage Roadway construction of a borehole. The specific location as shown in Table 3.Table 3 Determination of the gas pressure of the drilling parametersHole IDDetermination of locationDrilling parametersDip/Azimuth/Drilling diameter /mmDrilling depth /mAEast return airway16117542BEast return airway4117599CEast return airway16117555DEast return airway301817548EEast return airway301817545.5FEast return airway301817546.5G3104 backplane Drainage Roadway18267546.5Observation time for a week, the results of gas pressure measurement are shown in Table 4.Table 4 The results of gas pressure measurementHole IDABCDEFGResidual gas pressure /Mpa0.010.020.010.020.010.010.023.3煤层瓦斯预抽率工作面投产前瓦斯抽出率计算公式：式中：工瓦斯抽出率，%；Q抽已抽出瓦斯总量，万m3；Q瓦储工作面瓦斯储量，万m3；Q储煤层资源储量，万t；W煤层气瓦斯含量，m3/t；K围岩瓦斯涌出量系数，取1.15。3104工作面和底抽巷瓦斯抽放管路安装有孔板流量计，每天对瓦斯抽放量进行记录。从2008年3月抽放开始到2012年4月工作面开始回采前，累计施工钻孔个数3819，钻孔工程量235137m，瓦斯抽放量845.37万m3；累计风排瓦斯量91.15万m3，共计936.52万m3（见表5）。3104工作面原始瓦斯含量20.60m3/t，煤层可采储量73.65万t。将数据代入式中得出： 表5 3104工作面瓦斯抽排量汇总表抽放地点抽排时间瓦斯抽放量（万m3）备注3104工作面瓦斯抽放量2008.03-2012.04845.373104工作面风排瓦斯量2010.5.10-2012.2.2891.15合 计936.523.4防突效果评价3.4.1钻孔指标根据该矿资料，二1煤层瓦斯抽采钻孔有效抽采半径为2.85m。3104工作面上、下顺槽布置本煤层钻孔预抽工作面煤层瓦斯，上顺槽上帮钻孔呈双排排列，孔间距1.5m，排间距0.5m，孔深60m，孔径94mm；下顺槽下帮钻孔呈双排排列，孔间距1.5m，排间距0.5m，孔深7073m，孔径94mm。在3104外切割向工作面布置本煤层钻孔预抽工作面煤层瓦斯，钻孔孔间距1.5m，孔深60m，孔径94mm。在3104切眼向工作面布置本煤层钻孔预抽工作面煤层瓦斯，钻孔孔间距1.5m，孔深60m，孔径94mm。在3104第一中切眼向工作面、外切割方向布置本煤层钻孔预抽工作面煤层瓦斯，钻孔孔间距1.5m，孔深80m，孔径94mm。3104底板抽放巷布置穿层钻孔预抽工作面煤层瓦斯，孔间距0.5m，排间距0.5m，孔深30m，孔径94mm。工作面开切眼至停采线长度548m，采面平均长度120m，通过上下顺槽相向施工钻孔，保证了采面没有空白带。钻孔布置满足“抽放钻孔控制整个预抽区域并均匀布孔，沿回采工作面走向、倾向和煤层厚度没有空白带”。3.4.2瓦斯指标1）瓦斯含量指标3104工作面共布置了14个瓦斯含量测定钻孔，其中3104工作面上顺槽7处，3104工作面下顺槽7处。经实测，3104工作面残余瓦斯含量为2.855.07m3/t（除去漏气煤样），符合煤矿瓦斯抽采基本指标（AQ1026-2006）第4.1条“煤层瓦斯含量降到8 m3/t一下”的规定。2）瓦斯压力指标根据3104工作面实测残余瓦斯压力数据，残余瓦斯压力0.010.02MPa，符合煤矿瓦斯抽采基本指标（AQ1026-2006）第4.1条“煤层瓦斯压力降到0.74 MPa（表压）一下”的规定。3.4.3煤层瓦斯预抽率3104工作面煤层瓦斯预抽率为53.7%，大于煤矿安全规程第190条第2款“煤层瓦斯预抽率大于30%”的规定。综上所述，3104回采工作面在采取了预抽煤层瓦斯措施和长时间的排放后，各项指标均符合消突效果评价的相关判别标准，因此，3104回采工作面已经消除了煤与瓦斯突出的危险性。4、评价结果的可靠性分析4.1评价单元划分的合理性“在进行预抽回采工作面煤层瓦斯防突措施效果评价时，如果评价范围内各钻孔的抽排时间差别过大及钻孔间距过大，则应将评价区域划分为不同的评价单元分别进行评价”6 State Administration of Work Safety, State Administration of Coal Mine Safty. (MT/T1037-2007) Evaluating Method of The