Simulation Experimental Study On Air Leakage Law And Gas Migration Rule In The Goaf

With the continuous development of the shallow coal resources and mine mining strength increasing,, working face gas emission overrun has become the bottleneck; of restricting safety production in coal mine. The main source of gas emission from working face is goaf gas emission, so it is necessary to know concentration distribution and migration rule in the goaf before to manage working face gas emission overrun. The main driving force of gas migration in the goaf is air leak, which is the immediate reason for the upper corner gas concentration overrun in the goaf and the left coal self-igniting. Under the condition of blowing-out and no other driving force, gas migration is dependent on gas emission source term driving air to flow to the pressure boundary, forming percolation field, the intensity of which is decided by the intensity of gas emission source term, which is relatively feeble in general, and gas discharge is also completely slow, so this paper takes no account of the delivery law of methane under this circumstance of this driving force. This paper mainly studies on Air leakage law in the goaf and Gas migration rule under no gas extraction such as U ventilation system and tail roadway drainage gas and high position bores with tail roadway drainage gas.This paper first analyzes gas migration external environment including the structure of overlying strata and Gas emission source and influence factors of the gas emission, and systematically summarizes gas migration characteristics and the basic law of gas flow in the goaf by means of theory in porous media, and taking the similarity theory to analyze the simulation test model to flow similitude theorem and condition of similarity and similitude criterion.The paper with theory of gas flow and theory of similarity as a foundation established similar simulation test model which is based on the shaqu mine14025working face of actual size. The paper with method of theoretical analysis and experimental, makes analog simulation by means of pressure energy measuring and tracer technique under under no gas extraction such as U ventilation system and tail roadway drainage gas and high position bores with tail roadway drainage gas. In a similar model according to measuring wind pressure and wind speed, the paper analyses the source and sink types of air flow and flow direction and tendency of distance which is apart from working face, and sums up the air leakage rule. The paper summed up the gas concentration distribution and migration rule through measuring the gas concentration under three different driving force, drawing broken line graph for tendency of gas concentration along toward and along the tendency, Compared the influence of gas concentration distribution under the same ventilation system different pressure and different ventilation system and pressure.By comparison and analysis, the author finds that the gas concentration curve tends to migrate to deep goaf with the transformation of three different driving force, the harnessing effect on the upper corner gas is the best when high-order borehole group and gas tail roadway conduct pump drainage at the same time, however, this method is still having some limitations. Through studying the air leakage law of goaf, as well as the concentration distribution and the displacement and movement law of gas under three different driving force, so as to provide justification for gas control on spontaneous combustion "three zones" of the goaf and the upper corner in the production practice.