School of Resources and Civil Engineering,Northeastern University
Key Laboratory of Ministry of Education on Safe Mining ofDeep Metal Mines,Northeastern University

下煤层积水采空区上采用“上垮-下柱”方式复采上煤层带来严重的安全稳定性与底板采空区突水问题。将下煤层煤柱群与承压性空区积水联合支撑的蹬空覆岩简化为半无限平面体,建立合理的力学模型,通过弹性力学求解,得到蹬空覆岩的应力场分布。引入Mohr-Coulomb准则,极值求解得到顶板覆岩最大破坏高度,再结合上煤层开采底板破坏深度,分析重复采动层间岩层稳定性状态,并提出了相应的判别指标。考虑层间隔水控制层与水头损耗,提出不同层间岩层稳定性状态下的突水判据,并揭示水平构造应力对重复开采稳定性的作用。兼顾重复采动稳定性、底板采空区突水、煤柱承载稳定性,给出不同工况条件下的评价方法与防治措施,包括合理的疏水降压措施与煤柱“柱旁充填”指标。研究结果表明:顶板应力场与采深、水平地应力、煤柱宽度、单个空区跨度、空区水压有关,采空区顶板破坏形态大致为“波浪形”;当安全系数T≥1,重复开采稳定性较差,未采取措施不易在上煤层采用长壁式垮落法开采;水压越大,可减轻煤柱承载,并使煤柱处于高围压条件下,煤柱稳定性较高,但高水压又易发生底板采空区突水;煤柱宽度越大,承担的平均支撑力越小,σy应力峰值越低,层向分布波动越小,σx应力同样越小,顶板与煤柱越不易发生破坏;侧压力系数大于1且越大,可有效提高上行重复开采的可行性;疏水降压后的水压值p1需同时满足可规避突水与煤柱失稳的条件,即pm

The method of “upper longwall-lower pillar” is adopted to re-mines the upper coal seam on the water-log⁃ged goaf of lower coal seam,which brings serious problems of safety and water inrush. In this study,the goaf overbur⁃den supported by coal pillars and confined water accumulation was simplified as a semi⁃infinite plane to establish areasonable mechanical model. Through the elastic mechanics solution,the stress field distribution of the overburdenwas obtained. The maximum failure height of the overburden was obtained by introducing Mohr⁃Coulomb criterion andsolving the extreme value. Combined with the failure depth of floor on the upper coal seam mining,the stability of in⁃terlayer strata was analyzed under repeated mining,and the corresponding discrimination indexes were put forward.Considering the interlayer water⁃resisting control strata and water head loss,the water inrush criterion under the differ⁃ent stability of interlayer strata were proposed,and the effect of horizontal tectonic stress on the stability of repeat⁃ed mining was revealed. Comprehensively considering the stability of repeated mining,the water inrush from goaf infloor,and the bearing stability of the coal pillars,the evaluation methods and prevention measures under different work⁃ing conditions were given,including reasonable drainage and pressure reduction measures and the index of “pillar⁃sidebackfilling” for the coal pillars. The results show that the roof stress field is related to mining depth,horizontal in⁃situstress,coal pillar width,single goaf span and water pressure,and the failure form of the roof in the goaf is roughly“wavy”. When the safety factor T≥1,the stability of repeated mining is poor,and the longwall caving method cannotbe used in the upper coal seam without taking sufficient measures. The greater the water pressure is,the less the coalpillar bears,and the coal pillar is under the condition of high confining pressure. Therefore,the stability of the coal pil⁃lar is higher,but the water inrush from the goaf in the floor is easy to occur under high water pressure. The larger thewidth of the coal pillar,the smaller the average supporting force,the lower the peak value of σy stress,the smaller theσx stress,and the less likely it is to be damaged. If the lateral pressure coefficient is greater than 1,it can effectivelyimprove the feasibility of upward repeated mining. The water pressure p1 after the drainage should meet the conditionsof avoiding water inrush and coal pillar instability at the same time, that is, pm < p1 < max ( pf, hd / 100 + pmax ).Otherwise,the water shall be completely drained,and then the “pillar⁃side backfilling” should be adopted by the sizeindex Wm0. The research can provide useful guidance for the safe re⁃mining of the upper coal seam by “upper long⁃wall⁃lower pillar” on the water⁃logged goaf,preventing water inrush from goaf in floor,improving resource recovery rateand reducing resource waste.

国家自然科学基金资助项目(52174070,52004052);中央高校基本科研业务专项资金资助项目(N2201003)

马凯,杨天鸿,赵永,等. 上行重复采动底板采空区突水及开采稳定性理论分析[ J].煤炭学报,2023,48(S1):37-46.

MA Kai,YANG Tianhong,ZHAO Yong,et al. Theoretical analysis of water inrush from goaf in floor and miningstability for upward repeated mining[J]. Journal of China Coal Society,2023,48(S1):37-46