Analysis Of Coal And Gas Outburst And Research On Similarity Of Physical Simulation For It

Coal is the main energy source of our country.The share of coal in disposable energy consumption structure is about 64%in 2015,and coal energy's dominant position will not change for a long period.China's coal mining conditions are complex,particularly the frequency and the death of coal and gas outburst accidents are all at the forefront of coal mining accidents,coal and gas outburst has become a challenging problem of the safe production of coal.The study on the mechanism of coal and gas outburst,finding out the factors,conditions and development process are helpful to deepen the understanding of outburst.It is beneficial to study the similarity and mechanism of coal and gas outburst from the angle of similarity simulation experiment.In this paper,the test results of the coal body elastic properties and the gas expansion energy of briquette samples are obtained.Main outburst potential energy including elastic energy of coal and expansion energy of gas and main energy consumption including crushing work and throw work of coal were analyzed,and energy equations were build.The main energy sources are analyzed.The methods and difficulties of establishing similarity criterion are analyzed.Research on similarity criterion of coal and gas outburst was conducted.Under the guidance of similarity criterion,the similar material of coal and the similar gas of methane are developed.The advantages and disadvantages of coal and gas outburst simulation test instrument are analyzed,a large scale simulation test instrument is developed.Research conclusions were mainly reflected in the following aspects.(1)Energy exchange of briquette specimen occurred under uniaxial compression loading,and a part of the total input energy converted to elastic energy.Elastic energy near peak strength reached its maximum which accounted total input energy for about 70%,and the elastic energy was released quickly after peak strength.Expansion energy of gas of briquette specimen changed barely before the peak intensity,but it increased 25%suddenly on peak intensity and caused mutations of the potential energy of outburst.(2)Elastic energy of coal and expansion energy of gas are the main energy of outburst,and crushing work of coal and throw work of coal are the main modes of energy dissipation.Calculation method of potential energy and consumption energy of outburst was deduced,and gas outburst energy equation which accorded with dimensional homogeneity was obtained.Numerical calculation of energy equation was conducted and a result was obtained that the expansion energy of gas is the most dominating energy of outburst,and it is more than an order of magnitude lager than the elastic energy of coal.(3)Similarity criterion was deduced based on energy equation,and some similarity numbers of parameter relationships including unit weight,porosity,absorptivity,elasticity modulus,Poisson ratio,cohesion,angle of internal friction.A set of practical and convenient similar scales were obtained according to similarity numbers.(4)The humic acid sodium aqueous solution as the coal similar material cementation agent basically does not change the coal adsorption,and the concentration of cementing agent can adjust the strength of the similar material.At the same time,unit weight and porosity of similar material consist with that of raw coal under the pressure of 15MPa.This similar material fits well with the physical and mechanical characteristics and similar criterion of coal.Binary gas mixture of C02 and N2 with various concentration ratios is an ideal similar gas of methane,and it has greater similarity and security.(5)Large physical simulation test device of coal and gas outburst was build,of which the system modules included reaction and sealing unit,load and control unit of crustal stress,load and control unit of gas,driving and control unit of micro tunnel,multi physical quantities information acquisition unit.This test equipment has rational model space and high sealability,and it supports true three-dimensional loading.The instrument has the function of automatic simulating excavation,at the same time,it is more automated,informational and safety.