基于岩层移动类双曲线模型的水资源“浅保-深储”方法

“Shallow preservation⁃deep storage”method of water resources based on analogous hyperbola model of overburden movement caused by coal mining

针对煤炭开采导致地下水位下降和地表植被破坏等生态问题,基于保水采煤的科学内涵和采动覆岩移动类双曲线模型,建立了采动覆岩不同层位含水层“浅保-深储”差异化保护方法。即在上覆岩层破坏损伤最窄的主关键层下离层区注浆控制其上部岩层不破断,保护潜水水位和地表生态;其下部破坏的含水层利用采空区垮落岩体的空隙储存起来,经自净化后再利用。“浅保-深储”模型融合了采空区充填和煤矿地下水库保水的各自优势,并给出其适用的覆岩条件。根据采动覆岩“类双曲线”破坏移动特征,理论推导了主关键层下离层区初次注浆、周期注浆步距以及注采比,分析了注采比受主控参数的影响规律,得知注采比随垮落角和主关键层与煤层间距的增大而减小,随充分采动角和工作面推进距离的增大而增大。采用现场实测注浆数据对理论注采比进行验证,2者基本吻合。采用数值模拟对比分析了覆岩含水层“浅保-深储”、采空区充填保水地下水库的储水效果和煤柱稳定性,获得了采动覆岩移动和地下水流动均具有显著的“类双曲线”特征。基于理论注采比在主关键层下离层区注浆能够实现不同层位含水层“浅保-深储”,且该保水方法煤柱支承压力最大可降低60.8%,显著提高了储水采空区隔水煤柱的安全性,解决了井下采煤与充填难协调问题,利于煤炭绿色、安全、高效开采。

In order to solve the mining⁃induced ecological problems,such as the groundwater level declining and sur⁃face vegetation destruction in the mining area,based on water⁃preserved coal mining and analogous hyperbolic move⁃ment of overburden,this paper proposed a differential protection spatial model for different layers of groundwater,named“shallow aquifer preservation⁃deep aquifer rstorage”.Namely,the bed separation zone under the primary key stratum is grouted to control the upper rock layers and protect the shallow aquifer.The damaged aquifer below the primary key stratum is stored in the goaf,which will be reused after self⁃purified.The new water⁃preserved coal mining method can effectively integrate the advantages of goaf filling and traditional underground reser⁃voir on water protection,and its applicable overburden conditions are given.According to the analogous hyperbo⁃la model of rock strata movement,the theoretical initial and periodical filling holes distance,and the filling ratio of sep⁃aration zone under primary key stratum is derived.The variation of theoretical filling ratio is analyzed as the key pa⁃rameters increase,which include goaf angle,full subsidence angle,excavation width and the rock strata thickness be⁃tween primary key stratum and coal seam.The filling ratio decreases as the goaf angle and the rock strata thickness be⁃tween primary key stratum and coal seam increase,but increases with an increase of full subsidence angle and excava⁃tion width.Furthermore,the field⁃measured data of grouting under primary key stratum are used to verify the theoretical filling ratio,all of which are in good matches.In addition,numerical simulation is used to analyze the effects of“shallow aquifer preservation⁃deep aquifer storage”,goaf filling,and underground reservoir,as well as their abutment pressure distribution on coal pillars.Grouting under primary key stratum based on theoretical filling ratio can achieve a groundwater differentiated protection.Grouting improves the stability of the water⁃proof coal pillar of the wa⁃ter storage goaf and the maximum abutment pressure coal pillar can be reduced by approximately 60.8%.The pro⁃posed method significantly improves the coal pillars safety of the underground reservoir,and it also can solve the prob⁃lem of difficult coordination between underground coal mining and filling.Differentiated protection of aquifers is con⁃ducive to achieving green,safe,and efficient mining.