Study On Energy Source And Energy Dissipation Mechanism Of Coal And Gas Outburst

Coal and gas outburst is an extremely complex gas dynamic phenomenon in the underground mining process and has long been a threat to coal mine safety production,which is one of the most urgent problems to be overcome in the process of coal mine production.The process of coal and gas outburst is essentially the process of energy accumulation and dissipation.In this paper,the coal and non outburst coal are studied for the energy source and the energy dissipation process of coal and gas outburst deeply explored by laboratory experiments and theoretical analysis.Some progress has been made in the following aspects:(1)In order to analyze the effect of gas adsorption in coal and gas outburst,a high pressure gas instantaneous symmetrical pressure relief test device was developed.This device mainly consists of 4 parts: loading system,charging system,temperature and gas pressure detecting system and instantaneous symmetrical pressure relief system.With the following characteristics: to be instantaneous pressure relief experiment for the constant pressure adsorption for a period of time of coal under different gases and different pressures conditions;due to the symmetric pressure relief system to ensure instantaneous pressure relief while to be also considered the balance of the force balance of coal sample,the shortage of the traditional one-way coal-gas-outburst testing device is overcome;to provide axial pressure device for simulating in-situ stress in process of coal and gas outburst.(2)Through the theory of coal particle shape analysis shows that the particle shape has great influence on the determination of surface area.In the calculation of crushing energy,the coal particles are regarded as spherical and the crushing energy is the lowest;coal microscope observation results show that,whether outburst-prone or non outburst-prone coal,particle shape is basically similar when the coal is broken down to 0.075 mm,and the shape of the particle is most of the ellipsoidal and spherical.And the shape of these tiny particles is not related to the fragmentation of the former block,the way and the size of the applied energy and the crushing process.Which provides the basis for the calculation of the new surface area of the broken particles by the surface area.(3)When the outburst-prone and non outburst-prone coal are broken down to 0.075 mm,the cumulative mass of the coal particles under the sieve obey logistic distribution,and the mass distribution above sieve is different,outburst-prone coal obey Gauss distribution;and non outburst-prone coal obey normal distribution.Which provides an auxiliary means for the identification of outburst-prone coal and non outburst-prone coal,and provides the experimental guidance for the accurate calculation of the coal and rock crushing energy.(4)When the coal is broken,the proportion of small particles below 0.075 mm are not much,but there is a large surface area.The specific surface area of outburst-prone coal and non outburst-prone coal is increased with the increase of energy.The specific surface area of the outburst-prone coal is 1~2 times higher than that of the non outburst-prone coal with the same energy.The crushing specific work of non outburst-prone coal is firstly decreased and then remained stable with the increase of energy,while that of outburst-prone coal is increased with the increase of energy.It shows that the outburst-prone coal is more easily broken under the same energy.After the coal broken,the relationship between the new surface area and energy can be exponential function.The smaller the coal broken,the more stable the shape of the particle,the greater the difficulty of further fragmentation,and the more crushing energy to achieve the same broken increment.(5)When the temperature effect is not considered,the Langmuir equation is expanded into Taylor series and the first two items are retained.the gas adsorption for external acting calculation has been simplified to obtain the formula of gas desorption expansion.The calculation shows that the capacity of gas expansion depends on the gas adsorption constant for different gas.(6)According to the theoretical analysis,it is known that,under the same conditions and without consideration of adsorption,the expansion work is the same for different gas instantaneous pressure relief experiment;combined with experimental coal sample after fragmentation analysis shows that in the moment of pressure relief crushing coal adsorption experiment has played a great role because of the different of coal broken degree when the experiment of different gases.After application of axial compression,the degree of fragmentation of coal samples is increased,which shows that the coal body under the action of stress has a large number of cracks,the coal strength is reduced and the gas flow and storage space are also given,can gas expansion continue to destroy and smash the coal body when the gas pressure instantly reduces.(7)Based on the analysis of energy sources and energy dissipation in process of coal and gas outburst,the energy equation of coal gas outburst was established.The energy,the accumulation of elastic strain energy during the deformation of coal-rock and the gas expansion energy produced by free gas and adsorbed gas desorption in coal body,can become the main energy source to destroy and throw the coal.Through the energy analysis of the outburst cases in the past,the expansion energy of gas in coal seam is less than that crushing energy of coal body,so the pore gas of coal is not enough to provide energy to coal gas outburst.In the outburst process,the amount of gas emission is much larger than that of the free gas in the pore,and the gas expansion energy is 3~4 orders of magnitude of the free gas expansion energy.(8)According to the outburst strength and highlight the end position,the strength of the smaller and prominent surface terminated before the peak stress,smaller outburst intensity and prominent terminated surface after the peak stress,the strength larger and prominent terminated surface before the peak stress,the strength large and prominent terminated surface in the peak stress after four coal and gas outburst energy conditions are obtained.