| The inclined coal seam under the aquifer will face many serious challenges during the mining process,including blind mining of coal resources without theoretical guidance and leaving waterproof(sand)coal pillars,which leads to problems such as water inrush from the roof and resource waste.In order to achieve safe production and improve resource recovery rate,this thesis takes the 312 inclined working face under the aquifer in Qinan coal mine as the research background.Through field investigation,laboratory testing,theoretical analysis,numerical simulation,and industrial experiments,the thesis studies the top breaking movement law and water control mining technology of the inclined working face under the aquifer.The main research results are as follows:(1)The key layer positions within the 100 m range of the overlying strata of the312 working face in Qinan Coal Mine were theoretically determined.Using elastic mechanics theory,the initial caving step distance of the 312 working face was calculated to be 29.8 m,and the periodic caving step distance was 14.8m.A basic model for the evolution of the top breaking process was established,revealing the stress characteristics,plastic zone characteristics,and fracture mode characteristics under the basic top caving of the 312 working face.(2)A discrete element numerical model was established to simulate the movement law of the overlying strata and the development characteristics of the caving fissures.The results were mutually verified with the mechanical model calculations,clarifying the caving step distances in different mining stages.The distribution characteristics of the "three zones" of overlying strata fissures were studied,and the height of the caving zone was determined to be 15.8 m,and the height of the water-conducting fissure zone was 49.6 m.It was also found that the upper overlying strata fissures were essentially compacted after sufficient caving and did not affect the normal mining of the working face,nor did they pose any safety hazards.(3)The working resistance of the hydraulic supports during the mining of the working face was monitored,and the data was analyzed to obtain the initial and periodic caving step distances of the 312 inclined working face,which were found to be 24.8-29.6 m and 13.9-22.1 m,respectively.This confirmed the rationality and accuracy of the calculated and simulated results.The monitoring results of the advanced support pressure showed that the influence range of the advanced support pressure on the two roadways of the 312 working face was within 40 m in front of the working face.Among them,the range of the pressure effect of the machine advanced support on the 312 working face was 18 m,with a peak pressure of 28.3 MPa,and the peak position was9.6 m away from the working face.The range of the pressure effect of the ventilation roadway on the 312 working face was 20 m,with a peak pressure of 31.2 MPa,and the peak position was 9.8 m away from the working face.Therefore,the reasonable distance between the advanced support and the working face in the two roadways was determined to be 20 m.(4)The safety water control technology process was clarified,and the height of the sandstone coal pillar was determined to be no less than 30.5 m through comparative calculations.The estimated water inflow during the mining process was 3.7-4.6 cubic meters per hour,with a maximum inflow of 6.1 cubic meters per hour.The numerical simulation revealed the permeability evolution law of the overlying strata during the mining process,and the results showed that the maximum depth of the permeability increase zone was about 50 m,and the maximum depth of the sandstone coal pillar was about 30.1 m.The calculation results of reasonable size of sand-control coal-rock pillar are basically consistent with the development depth of lateral permeability of sandcontrol coal-rock pillar under full mining,which indicates that the study of permeability evolution law can be applied to determine the reasonable size of sand-control coal-rock pillar.(5)A clear technical system for top water control mining was formed,with the principle of exploration first,then placement,and finally mining.The monitoring results of water inflow at the 312 working face showed that the maximum water inflow reached 6.0 cubic meters per hour,and then stabilized at 3.6-4.5 cubic meters per hour.This verified that the water control mining technology scheme was scientifically reasonable and effectively ensured the safe and efficient mining of the working face.This thesis includes 55 figures,18 tables,and 65 references. |
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