Study On Mechanism Of Dynamic Pressure Disaster In Fully Mechanized Face Under The Column Goaf Of Hanjiawan Coal Mine

Yu Shenfu coal mine which located in the interior of northwest mining area is main coal-production area in china,with the consumption of shallow resources,a unique mining condition under the shallow coal seam column goaf is formed during the exploitation of deep coal resources.Under this mining condition,the working face is prone to dynamic pressure disasters.Researching the formation mechanism of pressure disasters and proposing the corresponding control measures are not only the urgent needs of coal mining enterprises,but also have great significance for implementing the spirit of the 19 th Party Congress thoroughly— making a new pattern of safe production management.The paper relies on the Shanxi science and technology research development project “Study on the risk assessment and pre-control technology of the fully mechanized coal seam roof undrer the shallow buried small mine gob area”,which combined with the Hanjiawan Coal Mine 3301 working face in the Yu Shenfu Mining area,in view of the fact that it is highly probable dynamic pressure disaster will occur on the working face when mining under the upper column goaf.Through collecting,summarizing and analyzing the research results of dynamic pressure disaster accidents under such mining conditions,it is considered that it’s necessary to analyze the stability of coal pillars in the upper goaf in order to judge whether the working face will occur a pressure disaster.Through the analysis of the plastic zone based on the Mohr-Coulomb criterion and the coal pillar stability discriminant that the ratio of the plastic zone to the coal pillar width,which is established from the catastrophe theory.The result combined with numerical simulation analysis conclude that the concentrated coal pillars in the upper goaf are stable before the mining of the 3301 working face,while the other coal pillars have basically been unstable.It is preliminarily judged that the possibility of disasters is greatest when the 3301 working face advances below the concentrated coal pillar.Further research on the characteristics of roof movement during the mining process of the 3301 working face in the upper goaf is carried out by similar model experiment and numerical simulation.Model experiments shows that the inter-coal stratum fall by full thickness,the numerical simulation illustrates that the vertical shear stress of the overburden layer in the direction of the working face is higher andwider than these of other coal pillars when the working face advances exceed in the concentrated coal pillar.Based on the voussoir beam structure of key stratum theory,meanwhile applying two structures,working face pressure arch and open-off cuts pressure arch are used to analyze the causes of roof falling.It’s believed that there are two fundamental causes,first the working face pressure arch with effective bearing capacity cannot be formed when the working face advances exceed in the concentrated coal pillar;the second is that the front arch springing of the 2306open-off cuts pressure arch located on the concentrated coal pillar.The direct reason is the greater concentrated stress of concentrated coal pillar.Combined with voussoir beam structure and step beam structure analysis,the vertical shear stress is higher than other types coal pillars when the working face advances exceed in the concentrated coal pillar.eventually,the working face will have a full-thickness falling dynamic pressure disaster between the coal seams.According to the conclusions drawn from the research,the 3301 working face is highly possible to have a dynamic pressure disaster when exceed in the concentrated coal pillars.Two contral measures that filling the uncut compacted goaf of 2306 working face and pre-blasting concentrated coal pillar are proposed,finally selecting and implementing the method of pre-blasting concentrated coal pillars.The results of microseismic monitoring during the blasting process show that the coal pillars in the target area have been effectively loosened and blasted.The results of mine pressure monitoring at 3301 working face after blasting show that the working resistance of the support is below the rated working resistance,mine pressure appears to be decrease.