| With the priority of high filling efficiency,low cost,and slight influence on mining,overburden grout injection mining technology is frequently determined as dominated way by most coal enterprises to solve the problem of mining below constructions,railways and highways,rivers and lakes.The key of the technology is to accelerate the formation of sufficiently bearing area in the goaf by grouting filling material into overburden under high pressure,which cooperated with coal pillar to support key strata,creating a bearing structure comprising sufficiently bearing area,coal pillar,and key strata.So,good control effect of key strata directs the disturbed effect of surface subsidence.However,previous researches did not further study the control effect of key strata,but just carried out some orientated research on the supporting function of sufficiently bearing area and coal pillar on key strata.The paper has studied the structure model of overburden grout injection mining technology and its application,with theoretical analysis,numerical simulation,field simulation experiment and other research methods adopted.The paper has found the deflection mechanical model of key strata in the bearing structure of overburden grout injection,and deduced the calculation method of foundation coefficient according to constitutive equation of elastic foundation.The coal and rock layer,which located between the top of grout injection layer and the bottom of key strata,was regarded as elastic foundation.Deflection mechanical model of key strata was found according to differential equation of elastic foundation.Foundation of key strata was divided into pillar area,deficiently bearing area and sufficiently bearing area near pillar side,and deficiently bearing area and sufficiently bearing area near coal wall.And calculation method of elastic foundation coefficient was deduced according to constitutive equation of elastic foundation assumptions.Based on the deflection mechanical model of key strata in the structure of overburden grout injection and fundamental of probability integration method,predicting methods was found,and the effects of grouting and mining parameters on the control result of surface subsidence,was analyzed.key strata and unconsolidated layer was the main cause of subsidence,the subsidence of key strata was calculated though the deflection mechanical model,and was regarded equivalent to mining height,then surface subsidence was predicted though probability integration method.The turn of main causes that affect surface subsidence is grout layer height,width of working face,mining height,ratio of grout injection and mining,and width of coal pillar,according to the effect degree to the maximum surface subsidence.The estimate measure of partition coal pillar stability was established base on grouting-induced compaction area,and the parameterized design methods was perfected.The supporting effect of grouting-induced compaction area on overburden strata is different from that of partition coal pillar,which is related to injection-production ratio,and the larger the injection ratio is,the more obvious the supporting role is.The long-term stability of the partition coal pillar is mainly influenced by the width of partition coal pillar,the injection-production ratio and the distance between coal seam roof and the grouting layer.Based on the foregoing research results,the design method and process of the overburden grout injection mining parameters were improved.Based on above research results,field study of the overburden grout injection technology were carried out during mining in Panel 101 of Liudian coal mine.The design width of Longwall mining was 154 m,the design width of partition coal pillar was 40 m,the design width of the distance between coal seam roof and the grouting layer was 90 m,the injection-production ratio was 50%,the predicted surface subsidence was 464 mm.he measured surface subsidence was 451 mm when the technique was successfully operated,and the villages were saved. |
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