Study On The Law Of Influence Of Gas Expansion Energy And Extension Analytic Hierarchy Prediction Method Of Coal And Gas Outburst

Coal has long been the main energy source of China.However,after long-term large-scale development,shallow resources are depleting,and the exploitation of deep coal and high gas coal seams is an inevitable problem.The gas threats faced by deep mining wells are becoming more and more serious.The prediction and prevention of coal and gas outbursts are very severe,has become a worldwide problem and research hotspot,and has become a scientific problem that needs to be solved urgently in the safe production of high gas mines in China.It is an important strategic demand and breakthrough direction for national energy security.From the energy point of view,the outstanding energy mainly comes from gas expansion energy.Therefore,it is important to study the gas expansion energy of coal body and its influencing factors to predict coal and gas outburst.At the same time,the gas expansion energy can be used as an important indicator for predicting coal and gas outburst,and an effective coal and gas outburst prediction and warning method can be established to avoid or reduce the occurrence of casualties,reduce the amount of anti-burst engineering and time,and ensure the production of mining.Normal operation to ensure the safety of life and property downhole has important economic and social benefits.This paper optimized and improved the initial release gas expansion energy measurement system,and based on the system to carry out experimental research on the factors affecting gas expansion energy.Then,the gas expansion energy was used as an important part of the coal and gas outburst prediction and warning index system.Based on the physical model test,a combination of extension theory and fuzzy analytic hierarchy process was used to propose an extensional analytic hierarchy forecasting method and feasibility.The main findings of the test are as follows:(1)Optimized and improved on the basis of predecessors,a new initial release gas expansion energy measurement system was developed,and the system was introduced in detail,and the test procedures and precautions were formulated.The system adopts the modular design concept,which consists of four units:expansion unit,data acquisition control unit,high-pressure gas control unit and temperature control unit.The nozzle design,sensor layout and overall layout had been optimized and improved.Greatly improved the stability,air tightness,convenience and accuracy of the system.(2)The experimental results of the initial release of gas expansion energy are:1)In the interval of gas pressure 0.5?1.5MPa,the temperature drop of coal sample during the rapid gas emission is between 0.3?1.2?.The higher the gas pressure,the greater the temperature drop.The main reason is the high pressure gas depressurization and gas desorption endotherm,and the desorption caused by gas desorption can reach up to 0.5 ?.2)In the interval of gas pressure 0.5?1.5MPa,the gas expansion energy of coal particles is between 10.45?55.55mJ/g.The larger the gas pressure,the larger the gas expansion energy,and the two are linear.3)Under the same air pressure,the larger the nozzle area,the smaller the corresponding gas expansion energy.The larger the nozzle area,the smaller the slope of the expansion energy and the gas pressure.When the nozzle area is 1.13 mm2,the slope is 36.56,and when the nozzle area is 3.39 mm2,the slope is only 25.72.4)The larger the particle size of the coal sample,the smaller the initial release gas expansion energy,and the relationship between the gas expansion energy W and the average particle diameter d of the coal sample decreases negatively.The larger the nozzle area,the smaller the corresponding correlation coefficient a,b,k,that is,the smaller the gas expansion energy.5)The type of gas does not affect the linear relationship between gas pressure and expansion energy,but the slope of different gases has a significant difference.The slope of CO2 is the largest,which is 38.747,and the slope of CH4 is the second,which is 29.815.The slope of N2 is the smallest,only 24.97.That is,under the same adsorption gas pressure,the gas expansion energy relationship of the three gases is C02>CH4>N2.6)The effects of nozzle area,gas pressure,coal sample size and gas type on the initial release gas expansion energy are significant,among which gas pressure has the greatest influence on expansion energy,and coal sample size has the least influence on expansion energy.The influence of gas pressure,gas type,nozzle area and coal sample particle size on the initial release gas expansion energy decreases in turn.7)The greater the stress of coal and rock,the larger the gas expansion energy of the initial release of the original coal specimen,and the change of the expansion energy before the 75%peak strength is not large.The magnitude of the change in the expansion energy from 75%peak intensity to 100%peak intensity produces a sudden change in the slope,which is more than three times the original.The intensity of the expansion energy has been large until the post-peak period.(3)Based on the combination of extension theory and fuzzy analytic hierarchy process(FAHP),a coal and gas outburst extension analytic hierarchy prediction method based on physical model test was established.The method consists of six indexes,namely initial release gas expansion energy,ground stress,gas pressure,coal strength,gas velocity initial velocity index ?P,and firmness coefficient f.The prediction results were divided into four risk levels:no prominent risk(N1),low prominent risk(N2),medium outstanding risk(N3),and high outburst risk(N4).And conduct experiments through a self-developed physical model test system,the prediction results were in good agreement with the actual coal and gas outburst physical model test results,and the feasibility of the method in the physical model test of coal and gas outburst was verified.