Study On The Stratification Transfer Prediction Method Of The Mining Subsidence Based On The Key Geological And Mining Factors

A series of geological environment problems occur during coal exploitation and themining subsidence is the most prominent. Confirming the key factors of the mining subsidenceand finding more accurate method are the most important problems to be resolved for carryingout the idea of prevention first. Taking the Yushenfu coal mining area in northern Shaanxiprovince as our study area, this article selected the key geological and mining impact factors ofthe mining subsidence with grey correlation analysis method and stepwise regression analysismethod; it studied the basic law of layered structure and characteristics of overburdenimpacting the mining subsidence; it proposed stratification transfer prediction method,constructed the stratification transfer prediction model of the mining subsidence based on thekey geological and mineral factors, and verified the reliability and accuracy of the modelthrough engineering examples. The main conclusions are as follows:(1) The research confirmed the key geological and mining impact factors of the miningsubsidence in the Yushenfu coal mining area and constructed the prediction model of thesubsidence factor based on the key geological and mining factors. Taking the subsidence factoras reference system, the paper screened the key geological and mining impact factors of themining subsidence with grey correlation analysis method and stepwise regression analysismethod and selected four key geological and mining impact factors which are perturbationcoefficient, syntheical protodyakonov hardness of overburden, the ratio of mining depth andheight, width-depth ratio finally. With the multivariate statistical analysis method, theprediction model of the subsidence factor based on the key geological and mining factors isconstructed in the passage, and the test results show that the average error is10%, so theprecision of the model can meet application requirement. (2) The passage established framework model of layered structure of2-2coal seamoverburden and constructed18different types of layered structure in the condition of samedepth and bedrock thickness. On the basis of analyzing borehole data, the paper establishedframework model of layered structure of2-2coal seam overburden and bedrock. Taking thequantity of sandstone layers, the average thickness of sandstone and sand-shale ratio asvariables, the paper constructed18different types of layered structure under the condition.(3) The article researched the basic law of sandstone layers quantity impacting thesubsidence factor with three different methods which are classification of rock mass basicquality index, structure mechanics analysis and numerical simulation test, under the conditionof same depth and bedrock thickness. The research results show that: firstly, in the condition ofsame bedrock thickness, with the increase of the quantity of sandstone layers, the basic qualityand whole stability of rock mass become worse, so does the anti-interference ability of rockmass; secondly, under the effect of elastic deformation and same loads, the increase ofsandstone layer coefficient may increase the maximum tensile stress and maximum deflectionof the whole rock, which would magnify the intensity caused by the same loads; thirdly, in thecondition of fixed sand-shale ratio, the law that subsidence factor increases with the increaseof sandstone layer coefficient is discovered, and its change process includes three stages whichare rapid increase, slow increase and tendency of stability; fourthly, when the sandstone layercoefficient is more than70%, the subsidence factor tended to be stable, the effect of thequantity of sandstone layers can be neglected. Then the fitted equations of sandstone layercoefficient and subsidence factor under different sand-shale ratio are established.(4) The paper studied the basic law of the average thickness of sandstone impacting thesubsidence factor under the condition of same depth and bedrock thickness. The researchresults show that: firstly, in the condition of same bedrock thickness, with the increase of theaverage thickness of sandstone, the basic quality and whole stability of rock mass increase,and the anti-interference ability of rock mass is stronger; secondly, under the same loads, withthe increase of the average thickness of sandstone, the maximum tensile stress and maximumdeflection are decreased so that the affecting intensity caused by the same loads is reduced;thirdly, the law that subsidence factor decreases while the average thickness of sandstoneincreases is discovered, and its change process includes two stages which are rapid decreasedand tendency of stability. The fitted equation of the average thickness of sandstone andsubsidence factor is established.(5) The paper studied the basic law of the sand-shale ratio impacting the subsidencefactor in the condition of same depth and bedrock thickness. The research results show that: firstly, in the condition of same bedrock thickness, with the increase of the sand-shale ratio, thebasic quality and whole stability of rock mass increase; secondly, under the same loads, withthe increase of the sand-shale ratio, the maximum tensile stress and maximum deflection aredecreased so that the affecting intensity caused by the same loads is reduced; thirdly, in thecondition of fixed sand-shale ratio, the law that subsidence factor decreases while thesand-shale ratio increases is discovered; fourthly, when the sandstone layer coefficient is morethan90%, the subsidence factors corresponding to the different sand-shale ratios areconvergence, in this case the effect of the sand-shale ratio can be neglected.(6) According to the function of layered structure of overburden in the occurrence anddevelopment of mining subsidence, the research proposed the idea and method of thestratification transfer prediction. Considering the characteristics of layered structure ofoverburden, the paper holds that surface subsidence is the final result of mining disturbancethrough the effect of transfer and superposition by stratum, therefore, it proposed the objectivebasis, basic thinking and conditions of the stratification transfer prediction method.(7) The research constructed the stratification transfer prediction model and the wholestructure model of the mining subsidence based on the key geological and mining factors inthe trend main section of subsidence basin. Under guidance of the idea and method of thestratification transfer prediction, taking the models of probability integral method and “keystratum-voussoir beam” theory as the foundation, the paper constructed the stratificationtransfer prediction model of the mining subsidence based on the key geological and miningfactors in the trend main section of subsidence basin, and meanwhile corrected the subsidencefactor in the new model according to the key geological and mining factors, the quantity ofsandstone layers, the average thickness of sandstone and sand-shale ratio. Through theoreticalanalysis, the model was extended to the whole structure model.(8) The stratification transfer prediction model of the surface movement and deformationbased on the key geological and mining factors was established. Under guidance of the ideaand method of the stratification transfer prediction, the stratification transfer prediction modelof the surface movement and deformation based on the key geological and mining factors wasestablished, including subsidence, incline, curvature, horizontal movement, horizontaldeformation, distortion deformation and Shear deformation of any point in the main section ofsubsidence basin.(9) Through engineering examples, the research verified the reliability and accuracy ofthe stratification transfer prediction model of the mining subsidence based on the keygeological and mining factors. Taking three coal mines located in different regions and mining areas as examples, an empirical study on the stratification transfer prediction model of themining subsidence based on the key geological and mining factors in the trend main section ofsubsidence basin was done. The results show that: not only does the model have high precision(the average error rate is about15%normally, the minimum error rate is less than1%), butalso the prediction precision of the model can be improved on the boundary of the trend mainsection of the subsidence basin relative to the model of probability integral method.