Coupling Mechanism And Coordination Technology Of Underground Coal Mining And Mine Reclamation In Coal-Grain Overlapping Areas Of Eastern China

Coal will remain the dominant energy source in China for a long time in the future,and will play the role of stabilizer.Cultivated land in China are increasingly scarce,and its protection will continue to be placed in a more prominent position in the future.Coal and grain have nothing to do with each other,but there is mutual "competition" when the space occurs overlapping.Surface subsidence is a land damage problem that accompanies coal mining.For this reason,"coal mining" or "grain production" in the coal-grain overlapping area is a key scientific issue that needs to be coordinated and resolved urgently.For a long time,the development model of "aboveground obeys underground" in coal mining areas is a one-sided view of resource utilization that ignores the coordinated development of resources and land.Mining subsidence in eastern China has resulted in large-scale ponding in cultivated land is a typical problem,and a heavy price has been paid for it.However,traditional reclamation is a typical model of "mining first,then destroying,and then treating".It cannot be carried out in contiguous ponding after stabilization,resulting in low recultivation rate,low utilization rate of land resources,and long time of land abandonment and degradation of the ecological environment.With the implementation of the balance of cultivated land occupation and compensation and the balance of increase and decrease,the terminal reclamation model no longer meets the needs of social development.Thus,it is necessary to adopt concurrent mining and reclamation(CMR)of "source protection,process reclamation" underground mining and recovery technology for underground coal mining.Based on theoretical analysis and scenario simulation of CMR,this thesis constructed the skip-panel and full-panel width model according to the critical damage subsidence value of cultivated land,puts forward the CMR for sinking reduction,predigging earthwork and mining-reclamining coupling,analyzes the input-output benefits through Guqiao Coal Mine of China,and gives some suggestions for the coordinated development of underground coal mining and cultivated land protection.The main work and relevant conclusions are as follows:(1)Clarified the interaction relationship between underground coal mining design and mine reclamation,and revealed the coupling principle of underground coal mining design and land reclamation.The space-time impact of coal mining design on land reclamation is revealed: development design > preparation design > panel design > coal mining method.The impact of coal mining method on land reclamation is real-time,which is also the focus of CMR.The requirements of the key technology of land reclamation on the temporal and spatial distribution of subsidence are discussed.It is proposed that the coupling of coal mining and mine reclamation needs to carry out the simulation of multi-scenarios before mining,the implementation of multi-stage dynamic reclamation during mining,and the monitoring of multi-frequency reclamation effect after mining,in which the pre-mining mainly focuses on the optimization of reclamation layout,design elevation and digging depth.The mining process mainly focuses on the optimization of reclamation timing,construction elevation and earthwork allocation.After mining,it focuses on the monitoring of design elevation of reclamation and the evaluation of reclamation effect.The interaction between protection,coal mining,subsidence,damage,and reclamation is clarified in space.In terms of time,it reveals the internal relationship between pre-mining,duringmining,post-mining and pre-reclamation,during-reclamation,post-reclamation.In terms of technology,the coupling of reduction damage and mine reclamation technology is proposed.(2)The model of skip-panel and full-panel width based on the critical damage of cultivated land is constructed,and the damage-reducing CMR of cultivated land underground is proposed.Based on the characteristics of cultivated land damage caused by coal mining in the coal-grain overlapping area of eastern China,it is considered that the critical damage subsidence value of cultivated land can be preferentially selected for reducing subsidence.The relationship between surface subsidence,panel width and mining sequence is analyzed,the characteristics of cultivated land damage using skippanels and full-panels are revealed,and the optimal principle of critical panel width for protective mining under cultivated land is proposed.A single-panel width model targeting the critical damage subsidence value of cultivated land was constructed.Considering the superimposed effect of mining subsidence in adjacent panels,the critical width model of the coal pillar under the repeated disturbance of multi-panels was constructed,which realized the purpose of normal cultivation of cultivated land during the skip-panels stage.Based on the coupling principle of underground coal mining,subsidence prediction,damage prediction,damage reduction from source,the design framework of the damage-reducing CMR in the coal-grain overlapping area is proposed.(3)The relationship between the key technology of CMR and underground coal mining and land subsidence is revealed,and the soil-conserving CMR technology in the coal-grain overlapping area is proposed.It is believed that the reclamation design elevation should focus on the critical damage subsidence value of the mined cultivated land;The construction elevation of the filling zone is proposed to be divided into:(i)the outer boundary elevation of the filling zone,(ii)the stripping elevation of the topsoil in the filling zone,and(iii)the pre-filling elevation of the filling zone.At the same time,the filling thickness model and control method are proposed,and the advantages and disadvantages of filling elevation control and thickness control are compared and analyzed.The maximum digging depth and the optimal digging depth in the subsidence area are proposed,and it is believed that the underwater digging depth determines the optimal digging depth,which is constrained by the difficulty and cost of underwater digging erathwork.The layout principle of the digging zone and filling zone is explored,and the calculation method and optimization framework of the water-land boundary line are proposed.It is proposed to refine the reclamation layout from outside to inside:(i)undisturbed zone,(ii)cut height zone,(iii)low pad zone,(iv)filling zone,and(v)digging zone.It is proposed to divide the reclamation timing into(i)the pre-reclamation timing of digging zone,(ii)the timing of topsoil stripping in the filling area and(iii)the timing of filling.It is believed that the optimization of reclamation timing should reduce the cost of reclamation and dige more soil resources as much as possible,and objectively analyze and choose the optimal reclamation timing according to local conditions.The subsidence area is proposed to be subdivided into stages of digging zone,stage filling zone,digging sub-area,and filling sub-area,and the principle and method of soil-conserving CMR stage division are given.The soil allocation optimization method and construction strategy of soil-conserving CMR are explored,and the design framework of soil-preserving CMR is summarized.(4)The coupling CMR technology of coal-grain overlapping area is proposed,and the reclamation effects under different mining layout and mine reclamation schemes are simulated,and the advantages and disadvantages of each scheme are compared.Combining the damage-reducing CMR and the soil-conserving CMR,a coupling CMR technology in coal-grain overlapping area is proposed.The coupled CMR has the following advantages:(i)The reclamation rate is high,which can increase the reclamation rate by 45.90% compared with traditional mining and reclamation schemes;(ii)Extend of reclamation timing and the service life of cultivated land for 14 years;(iii)The reclamation period is shortened by 42.31% shorter compared with the damagereducing CMR;(iv)The mine reclamation efficiency is high,and a single larger-scale reclamation can be realized;(v)The coal recovery rate is high,and the recovery rate is52.62% higher than that of the damage-reducing CMR;(vi)The effect of mine reclamation is quick,the surface subsides quickly and the settlement period is shortened when mining coal pillars;(vii)Make full use of land resources,shortening the land abandonment time compared with damage-reducing CMR and traditional reclamation schemes;(viii)The coupling degree of underground coal mining and mine reclamation is high,which meets the requirements of sustainable development of the mining area.(5)The input-output benefits of different coal mining and mine reclamation schemes in the coal-grain overlapping area were analyzed,and some suggestions for the coordinated development of coal mining and cultivated land protection were given.Traditional reclamation has lost its advantage of low reclamation costs with the accumulation of young crop compensation fees and the implementation of cultivated land index fees.Instead,the soil-conserving erathwork and coupling CMR pay more for reclamation costs in exchange for more cultivated land,thereby greatly reducing the compensation fees for young crops,cultivated land occupation tax and cultivated land index fees paid by enterprises.Damage-reducing CMR sacrifices coal recovery rate in exchange for land reclamation rate,but significantly reduces coal mining benefits.From the perspective of comprehensive benefits,soil-conserving CMR is the ideal choice for coal enterprises that have been put into operation.However,when the overpayment of compensation for young crops and the loss of social and ecological benefits exceeds the new costs in the mine,coupling CMR will be the best choice.The CMR technologies of damage-reducing,soil-conserving and its coupling for underground coal mining proposed in this thesis are suitable for different mining layouts and mine reclamation needs of coal enterprises,and enrich the concept and approach of coordinated development of coal mining and cultivated land protection in coal-grain overlapping areas.The thesis contains 109 figures,33 tables,and 248 references.