| The research on the overburden control of high efficiency paste backfilling working face is a complex system engineering,which involves mining,backfilling,supporting,subsidence,safety,etc.Currently,there is no complete solution of high relevance,covering from theoretical design to production practice.With the references to the previous studies in this paper,the comprehensive research methods of field research,laboratory experiments,theoretical analysis,MATLAB computer programming analysis,numerical simulation and engineering practice are combined to solve the low capacity of coal mine paste backfilling and the high cost of backfilling.With 3# coal seam mining beneath the buildings in Lu'an region taken as the research object,a series of researches on paste backfilling working face overburden control were carried out,which is an important direction to realize the sustainable development of coal mine production.The main achievements are as follows.(1)The research on high efficiency paste backfilling working face rock stratum control.At present,some coal mines in China have carried out the industrial practices large-mining-height and high-efficiency paste backfilling of cancellation isolation shift and solidification shift,but the theoretical research does not keep pace with the production practice.As per the paste backfilling coal mining face bracket,the interaction mechanism between filling body,the direct roof and lower basic roof,mechanical models for the paste backfilling working face rock stratum control at pre-mining stage,trial-mining and trial-backfilling stage,and the mining-backfilling stage were established respectively.Based on the Matlab program analysis,the bending and deformation of statically indeterminate beams is transformed into a piecewise independent integrated integral method for solution and derivation,with the analytical expression of relevant parameters obtained.Meanwhile,the instability discriminant analysis program method of roof rock beam damage of which the filling body unit strength changes as time goes was established,laying the theoretical foundation for the researches on the influence of the maximum face width,different filling paces and hydraulic brackets load on the mining and filling design.The theory of strata control in paste backfilling working face is the theoretical basis of support selection,filling body performance,filling technology and surface subsidence.(2)Case study and numerical simulation optimization.According to the theoretical model of strata control in paste backfilling working face,the effects of various filling paces and the hydraulic bracket loads on the mining and backfilling design were studied through the analysis of calculation examples;Based on the instability discriminant analysis program method of roof rock beam damage of which the filling body unit strength changes as time goes,a numerical calculation model which considers the change process of the filling body strength was established.As per various mining heights,filling and mining recycle,and different height filled body,the optimization analysis was carried out,which lays the foundation for numerical calculation.(3)The research on composite support system of paste backfilling working face.Based on the cooperative support system of "filling body + bearing strata + coal pillar",the concept of "filling body + bearing strata + roadway + coal pillar" composite support system is put forward.As per open-off cut excavation roadway along the roof,the scheme for large-section truss anchor support was proposed,then,the theoretical derivation and the simulation experiment was carried out,which suggests that the roadway can effectively control the subsidence of the roof and maintain the stability of the roadway;The stability analysis of the composite support system of "filling body + bearing strata + roadway + coal pillar" shows that the stability of the composite support system and the occurrence of surface subsidence can be effectively maintained and reduced only when the subsidence of roof before backfilling is controlled within 100 mm,the filling rate is more than 90% and the degree of compaction is more than 0.8.(4)Study on the influence of the key factors of the surface subsidence in the paste backfilling mining.In this paper,the law of conservation of pore volume is used to solve the problem of diffusion of pore in goaf caused by mining,and the relevant formulas of conservation law of pore volume in paste backfilling are summarized.By constructing the fuzzy extension model of the surface subsidence stability in the paste backfilling mining,the five key factors of controlling the surface subsidence are obtained,including the overburden structure,the amount of roof subsidence before backfilling,lacking distance of roof-contact,the strength of filling body and filling technology,and the optimization measures are given.According to the failure degree of key factors,the subsidence model of paste backfilling mining in unstable and stable state is established and analyzed.According to the prediction and analysis of the surface subsidence of Gaohe energy,the results show that the surface buildings can be used normally during and after mining and backfilling,and there will be no unsafe factors.(5)Engineering Applications.The investigation,sampling and experimental analysis of the composite structure of the overlying strata in the paste backfilling working face,the investigation and analysis of the distribution and deformation resistance of the surface structures and the basic conditions of paste backfilling mining system are carried out.Through economic cost accounting,paste backfilling mining can create about 61.8 million yuan of profit for Gaohe energy every year and can produce greater social benefits,which is an important demonstration effect in the whole Shanxi Province.There are 100 figures,21 tables and 165 references in the dissertation. |
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