| Gas prevention and control in coal mine has always been the focus of mine disaster prevention and control.Coal seam gas drainage is the main measure of gas control.In view of the low cost performance of polymer sealing materials commonly used in coal mine gas drainage boreholes,large particles of ordinary cement-based grouting materials and difficult injection.Through the research methods of stress analysis around the borehole,numerical simulation of air leakage,experimental study on the performance of sealing material and field measurement of sealing,the mechanism of action of new high flow sealing material on coal body is revealed.The main results of this paper are as follows :(1)Taking coal seam gas drainage borehole as the research object,the dynamic change model of coal permeability and borehole leakage was established to explore the influencing factors of borehole leakage.The diffusion model of different fluids in coal is deduced,which provides a theoretical basis for the ratio design of new high flow sealing materials.(2)The factors affecting the performance of the new high flow sealing material were analyzed,and the components of the new high flow sealing material were designed.Through the flow test and compressive strength test of sealing materials,the influence of polycarboxylate superplasticizer,water-cement ratio,expansive agent and retarder on the compressive strength,fluidity,setting time and expansion of slurry was explored,and the dosage range of each additive was determined.Then,the orthogonal experiment was designed by using the response surface orthogonal test method,and the response surface diagram and contour map were plotted by software to explore the interaction mechanism between the components of the material.The optimal ratio of the new high flow sealing material was determined as follows: 0.5% water reducer,0.04% retarder,water-cement ratio 1,and 8% expansive agent.(3)The self-designed sealing simulation platform was used to carry out the simulation test of borehole sealing,and the sealing effect of new high flow sealing materials and ordinary cement in coal was simulated.The new high flow sealing material and ordinary cement sealing material were injected into the coal body to form the consolidation body.Through the creep test,permeability measurement,nano indentation test and nuclear magnetic resonance test of the consolidation body,it is proved that the self-developed new high flow sealing material can better diffuse in the coal body.After consolidation,the microstructure of the coal body is changed,the critical gas pressure and coal permeability are changed,and the number of pores in the consolidation body is significantly reduced,indicating that the filling rate of the new high flow sealing material in the coal body is higher,and the mechanical properties of the consolidation surface of the new high flow sealing material and the coal body are improved,and the sealing effect is better than that of the ordinary cement sealing material.(4)The microstructure of the new high flow sealing material was analyzed,and it was found that the gel particles of the self-developed new high flow sealing material were connected and woven into a whole block.There were more hydration products,more sufficient hydration reaction,and dense overall structure,which increased the strength of the material,reduced the porosity,and effectively improved the performance of the new high flow sealing material.(5)Considering the dynamic changes of porosity and permeability of the injected coal,COMSOL software was used to study and analyze the seepage law of the new high flow sealing material in the fine pores of coal and rock mass.The results show that along the direction away from the borehole,the permeability increases sharply,decreases gradually,and finally recovers to the original permeability.With the increase of extraction time,the variation range of permeability around borehole also gradually increases.The variation law of volumetric strain of coal is basically consistent with that of permeability around borehole;with the increase of sealing grouting time,the slurry expansion area in coal seam gradually expanded,and the slurry expansion range changed greatly within 30 min before sealing grouting,and the slurry diffusion range changed little after 30 min.(6)Using the new high flow sealing materials in China coal xinji liuzhuang coal mine 150804 working face of tape along the groove of the gas extraction from drilling hole sealing field experiment was carried out,using the self-developed a new type of high flow hole sealing test of drilling hole sealing material,than in the average borehole gas concentration in the process of extraction using ordinary cement hole sealing material for sealing hole drilling increased by 51.18%,It is verified that the new high flow sealing material has good sealing performance.Figure 125 Table 30 References 232... |
