Study On The Prediction Methods Of Outburst Danger On Coal Roadway

Coal and gas outburst is one of the disasters threatening the production safety of coal mine.As the deepening of coal mining depth,the risk of coal seam outburst has been intensified constantly.Despite of the constant increase of safety technology investment on coal mine gas control,as well as the decrease trends of outburst accidents on casualty scale and intensity,outbursts were still existent.As compared to previous years,outburst accidents have seen great reductions in aspects of total number and casualties.However,rencent 5 years,there are still about 10 outburst accidents each year,causing about 50 deaths.In all kinds of outburst accidents,coal roadway outburst,with persistently high frequency and casualty proportion,is showing an increase trend.At present,the commonly-used prediction methods present some disadvantages and most of the outburst accidents are caused by inaccurate prediction on outburst risk.Besides,the methods used are inconsistent for the outburst predictions of different mining areas and coal seams.Meanwhile,the investigations to the sensitivity and reliability of prediction methods display certain disadvantages and are affected by many uncertainties.Therefore,it is urgent to avoid the influences of interference factors and conduct research on the prediction methods of coal roadway outburst using scientific experiment methods in the case of providing a unified experimental condition to each prediction method.In this study,ten representative coal samples were collected from 10 provinces in China and a simulation test platform for outburst risk prediction of coal roadways was established.The Initial Expansion Energy of Released Gas（IEERG）was used as the criterion to simulate the outburst risk of coal samples,and the coal roadway conditions of different outburst risk are simulated.Under the unified and known experimental conditions,various prediction index of outburst risk of the simulated coal seam is carried out,namely drilling cuttings index（S）,initial velocity of gas emission from boreholes（IVGEB）,gas desorption index of drilling cuttings（K₁,?h₂）and Initial Gas Emission from Boreholes（IGEB）.The experiment was carried out on 80 simulations of coal roadway outburst risk prediction（40 outburst and 40 non-outburst samples）and17 outburst simulation experiments,and the related auxiliary experiments were also completed.At the same time,the laboratory and filed experiments were carried out,which were based on the No.3 coal seam field conditions of Xinjing coal mine.The main conclusion and results are as follows:1)In view of the disadvantage of the current outburst risk prediction methods and evaluations of coal roadway,a method of evaluate the prediction index of outburst danger in coal roadway was proposed.That is,the IEERG can be used as a standard for assessed the outburst risk of the coal seams,and the conditions of simulation coal seams with different outburst risk were realized.Several outburst risk prediction methods were application on the simulation test platform.2)After the completion of 80 prediction test of simulated coal roadway,the conclusion of the sensitivity and accuracy of the test were reached.The results show that IGEB,with an accuracy rate of 92.5%,is superior to the other prediction method,it can distinguish the risks between outburst and non-outburst samples.In addition,the combination of various forecasting methods can be improved the accuracy and reliability of the prediction.3)The critical value of outburst risk prediction methods of coal roadway varies with the conditions of coal samples and gas type.The sensitivity of different prediction methods to gas and coal is also different.Therefore,for specific coal seam,it is necessary to study the sensitivity and critical value of these prediction indexes.In the laboratory,the platform can be used to quick predict the danger of roadway,the sensitivity and critical value of coal roadway outburst also can be prefect forecast.4)Take 3216 heading face in Xinjing coal mine as an engineering project,8different degrees of outburst risk simulated coal roadway outburst danger determination were accomplished in the laboratory.The critical value of the IGEB and the cuttings desorption index（K₁、?h₂）was obtained.The critical value of the IGEB is 47.34 L/m,and the test results are applied to the field prediction.5)The measurement uncertainty of each prediction method is calculated and analyzed.The uncertainty of manual measurement and reading should be avoided in the measurement of forecasting method.At the same time,the accuracy of measuring instrument itself is also an important factor that affects the accuracy and reliability of measurement results.