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In order to study the distribution of dust particle matter (including PM2.5) in coal workface, the concentration of total dust, PM10 dust and PM2.5 dust were measured with the dust concentration tester during the mining process in all roadways of Coalface 91324 that is the comprehensive mechanized coal face at a coal mine in Jincheng city. The results were analyzed and show that the total dust concentration is at its maximum 5 m downwind of the coal cutter while PM10 and PM2.5 dust fluctuates heavily in the coalface; the concentrations of three kinds of dust (the total dust, PM10 dust and PM2.5 dust) increase gradually and reach their maximum values at 330 m, then decrease slowly in the auxiliary return roadway. The concentration of these three kinds of dust fluctuates within the low concentration range in the main return roadway. In the main return roadway and auxiliary roadway the maximum levels of PM2.5 dust are 56.087 mg/m³ and 180.39 mg/m³ respectively. The PM2.5 dust is above the limit of ambient air quality. These findings provide the parameters for modifying the standard of dust testing and prevention. [ABSTRACT FROM AUTHOR]

After careful analysis of the regularity of ground surface subsidence in mined-out region and the characteristics of MMF curve model, a new time function model based on MMF model was proposed in consideration of the shortage of current ground surface subsidence predication models. Then the rationality of the new model was verified through project cases. The result indicates that the new model can give a good reflection of the regularity of ground surface subsidence in mined-out region and can accurately predicate surface subsidence. The predication values of the new model is a little greater than measured values on condition of proper measured data quantity, which is safe in the engineering. [ABSTRACT FROM AUTHOR]