Study On Mining Deformation Of Floor And Evaluation Method Of Water Inrush Mining Above Confined Aquifer

The study of mining deformation of floor is not merely of great scientific value for safetymining of coal mining above confined aquifer, but also provides crucial basis for control andmaintenance of surrounding rock in mining roadway.This dissertation aims to make systematic studies involving such aspects as stressdistribution of mining floor, floor stress and plastic zone distribution as well as deformationfailure law such as floor failure depth. The research results show that stress distribution modelof floor rock under the complete bearing pressure in the face based on the previous studies ondistribution regularities of bearing pressure enables to obtain the analytical solution of stressdistribution in any position inside the floor rock. Meanwhile, the stress distributionregularities computed by the stress of floor rock of mining face4602in Yangcun is of greatpractical applicability. And, the notion of floor rock failure depth is apportioned from theperspective of mining floor rock deformation. By employing numerical modeling softwareFLAC3D, six-factor and five-level orthogonal numerical simulation test of floor failure depthconcerning working face length, lithological association of roof rock and floor rock, miningdepth, mining height and dip angle was launched. Furthermore, the prediction model of floorrock failure depth where the lithological association of roof rock is considered for the firsttime which includes working face length, lithological association of roof rock and floor rock,mining depth, mining height and dip angle. On the basis of actual measurement and instanceson floor rock failure depth of corresponding mining faces in ten coal mines, it can beconcluded that this prediction model involves high precision which can meet the requirementof project.By on-site comprehensive actual measurement of floor rock deformation failure, theprocess and partition features of mine pressure behavior on floor rock, partition features offloor rock failure depth as well as relevance law between floor rock deformation andunderground pressure behavior were expounded in great details. In other words, bycomprehensive actual measurement of floor rock deformation, the influence of miningunderground pressure on floor rock is characterized by manifestation of pre-mining “leading”at a long-distance and continuity of post-mining “lagging”. In addition, both “leading” and“lagging” impacts have partition features. Based on the linkage effects between mining floorrock deformation and mining underground pressure, the perturbation action of miningunderground pressure on floor rock can be classified into “leading pressure-gatheringperturbation” and “post-mining pressure-relieving perturbation”, which provided the mechanical basis for explaining the mechanism of mining floor rock deformation failure.What’s more, floor rock undergoes two processes of leading pressure-gathering breakage andpost-mining pressure-relieving breakage. And, their breakage mechanisms are shearbreakdowns which are under the pressing condition in the early stage and is under the tensioncondition is the late stage. They are related in progression. That’s to say, post-miningpressure-relieving breakage made after pre-mining pressure-gathering breakage can lead tofurther aggravation of failure degree. However, it involves no extension effects as to miningfailure depth.On the basis of actual measurement data on70groups of floor rock failure depth, floorrock depth and the regularities of its influential factors were explored. Besides, the predictedgenetic-improved genetic algorithm optimization BP neural network model and PSOoptimization SVM model by floor rock failure depth were constructed. Based on MATLABsoftware platform, non-linear predicted model system of floor rock failure depth wascompiled, which could achieve fast and accurate prediction of floor rock failure depth.Finally, three-level evaluation model of floor rock water inrush in mines was establishedin order to achieve multistage distribution and screening progressive evaluation predictionfrom thickness to thinness and from empirical judgment to mechanical analysis on floor rockwater inrush in mines. To be specific, three-level evaluation model refers to primary judgment,detailed judgment and accurate judgment of floor rock water inrush in mines. Firstly, thecriterion of primary judgment is critical equation P=0.0025M2-0.0865M-16.8534/M+2.2440which is obtained by investigating and analyzing water inrush points of354mining faces inseven mining areas in North China and Lianshao mining area in Hunan Province,202roadway water inrush points and318safety actual mining faces, and then adopting themethod of mathematical statistical regression. The form of this critical equation is inaccordance with that of weak plate of homogeneous crack model P-M in terms of theconsideration of dynamic water pressure. As for the detailed judgment of floor rock waterinrush in mines, it is a further judgment on the possible water inrush occurrence areas basedon the primary judgment. What’s more, aggregative indicator method has taken severalinfluential factors on floor rock water inrush into account. Due to this judgment, it is muchmore comprehensive. Considering model simplification, the evaluation model of floor rockwater was built up based on inpervious intensity of expanding boundary. When it comes toaccurate judgment, it entails more specific prospecting on floor rock characteristics, aquifercharacteristics and occurring geological conditions. In this way, the meticulous and accuratefirst-hand data of water inrush evaluation areas needs to be mastered. Based on the above,mechanical stability analysis of floor rock was analyzed and then potential stability of floor rock under the influence of mining underground pressure and water pressure was determined.