浅埋近距离煤层开采房式煤柱群动态失稳致灾机制
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摘要
针对我国西部矿区浅埋近距离煤层房采煤柱下开采时易发生工作面压架、地表台阶塌陷以及矿震灾害的现象,采用物理模拟及数值模拟方法对下煤层工作面采动时上覆房采煤柱群的动态失稳过程及工作面压架机理开展研究。实测统计榆阳区部分矿井本煤层房式开采后,只有当房采煤柱的弹性核区比例大于31%时,房采煤柱才能处于长期稳定。下煤层采后的模拟结果表明:上覆房采煤柱的破坏形式及其失稳次序同其与下煤层工作面相对位置密切相关,房采煤柱依次从工作面开切眼位置、工作面位置、采空区中部位置发生破坏及失稳,且工作面开切眼和工作面位置处煤柱多发生顺向采空区的斜切破坏,而采空区中部煤柱则发生垂向压裂破坏。根据石圪台煤矿数值模拟结果显示,上部2-2煤层房采后煤柱支承应力峰值由原岩应力2. 8 MPa增大至12 MPa,应力集中系数为4. 28;当下部3-1煤层工作面采后,上覆2-2煤层房采煤柱的支承应力峰值增大至30 MPa,应力集中系数达10. 71;下煤层工作面开切眼侧与工作面正上方的房采煤柱呈现横向不均匀承载特征以及受水平拉伸变形影响,最终导致边界处房采煤柱易出现对角斜切破坏模式。两侧边界煤柱失稳后,其顶板岩层瞬间发生整体拉剪破断从而引发矿震,顶板多层岩层以"整体运动"的形式急剧快速下沉并撞击底板,将采空区中部上方的房采煤柱压垮压塌,同时巨大的冲击力进而导致上下煤层间的岩层发生全厚切落,造成下煤层工作面发生切顶压架。实验发现从上覆房采煤柱群首个煤柱发生破坏至整体失稳运动并达到稳定,历时仅约为0. 45 s,其中,上下煤层之间的岩层发生全厚切落历时仅约为0. 05 s。
In the western part of China,mine disasters such as support failure,surface stepped subsidence and mine earthquake,are prone to occur when lower coal seam is extracted which is closely beneath the coal pillars left after room-and-pillar mining with shallow overburden. In this paper,physical modelling and numerical simulation method were adopted to investigate the dynamic instability process of upper coal pillar group and the mechanism of support failure under the influence of lower coal seam mining. According to the measured statistics in some mines after coal mining of Yuyang District,only when the proportion of elastic core area of the coal pillars is greater than 31% can the room coal pillars keep long-term stability. The simulation result after mining lower coal seams shows that the failure form and instability sequence of the upper coal pillars have close relations with the positions relative to the lower coal seam working face.The damage and instability of room coal pillar occur in the positions of open-off cut,working face,and the middle of goaf successively.Furthermore,the coal pillars in the open-off cut and working face mostly show horizontal shear failure,while the coal pillars in the middle of the goaf show vertical fracturing damage. According to the numerical simulation results of Shigetai Coal Mine,the peak abutment pressure of coal pillar in upper 2-2 coal seam increases from in-situ stress 2.8 MPa to 12 MPa after coal mining with the stress concentration factor at 4.28.After the lower 3-1 coal seam working face mined,the peak abutment pressure of the retained pillar in upper 2-2 coal seam continually increases to 30 MPa with the stress concentration factor up to 10.71.The open-off cut side of the lower coal seam working face showed uneven horizontally bearing with the coal pillar directly above the lower coal seam working face and the influence of horizontal tensile deformation are the main reasons for the diagonal failure mode of the boundary coal pillars.After the instability of two sides coal pillars,the roof instantaneously occur overall shear breakage,causing mine earthquake,and multi-layered strata in the roof settled suddenly in the form of "rigid body motion"and hit against the floor,leading to the collapse of the room coal pillars in the middle of goaf. At the same time,the huge impact force further leads to the full cutting of the strata between the upper and lower coal seams,which results in the roof cutting and support failure in the lower coal seam working face.It was found in the experiment that there was only about 0.45 seconds from the failure of the first coal pillar in the overlying coal pillar group to the overall unstable movement and the final stability,among them,the full cutting of the strata between the upper and lower coal seams only took about 0.05 seconds.
In the western part of China,mine disasters such as support failure,surface stepped subsidence and mine earthquake,are prone to occur when lower coal seam is extracted which is closely beneath the coal pillars left after room-and-pillar mining with shallow overburden. In this paper,physical modelling and numerical simulation method were adopted to investigate the dynamic instability process of upper coal pillar group and the mechanism of support failure under the influence of lower coal seam mining. According to the measured statistics in some mines after coal mining of Yuyang District,only when the proportion of elastic core area of the coal pillars is greater than 31% can the room coal pillars keep long-term stability. The simulation result after mining lower coal seams shows that the failure form and instability sequence of the upper coal pillars have close relations with the positions relative to the lower coal seam working face.The damage and instability of room coal pillar occur in the positions of open-off cut,working face,and the middle of goaf successively.Furthermore,the coal pillars in the open-off cut and working face mostly show horizontal shear failure,while the coal pillars in the middle of the goaf show vertical fracturing damage. According to the numerical simulation results of Shigetai Coal Mine,the peak abutment pressure of coal pillar in upper 2-2 coal seam increases from in-situ stress 2.8 MPa to 12 MPa after coal mining with the stress concentration factor at 4.28.After the lower 3-1 coal seam working face mined,the peak abutment pressure of the retained pillar in upper 2-2 coal seam continually increases to 30 MPa with the stress concentration factor up to 10.71.The open-off cut side of the lower coal seam working face showed uneven horizontally bearing with the coal pillar directly above the lower coal seam working face and the influence of horizontal tensile deformation are the main reasons for the diagonal failure mode of the boundary coal pillars.After the instability of two sides coal pillars,the roof instantaneously occur overall shear breakage,causing mine earthquake,and multi-layered strata in the roof settled suddenly in the form of "rigid body motion"and hit against the floor,leading to the collapse of the room coal pillars in the middle of goaf. At the same time,the huge impact force further leads to the full cutting of the strata between the upper and lower coal seams,which results in the roof cutting and support failure in the lower coal seam working face.It was found in the experiment that there was only about 0.45 seconds from the failure of the first coal pillar in the overlying coal pillar group to the overall unstable movement and the final stability,among them,the full cutting of the strata between the upper and lower coal seams only took about 0.05 seconds.
引文
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[14] ZHU W,XU J,XU G.Mechanism and control of roof fall and support failure incidents occurring near longwall recovery roadways[J].Journal of the Southern African Institute of Mining and Metallurgy,2017,117:1063-1072.
[15]孟达,王家臣,王进学.房柱式开采上覆岩层破坏与垮落机理[J].煤炭学报,2007,32(6):577-580.MENG Da,WANG Jiachen,WANG Jinxue. Mechanism on the failure and caving of roof strata in pillar and house mining[J].Journal of China Coal Society,2007,32(6):577-580.
[16]屠世浩,窦凤金,万志军,等.浅埋房柱式采空区下近距离煤层综采顶板控制技术[J].煤炭学报,2011,36(3):366-370.TU Shihao,DOU Fengjin,WAN Zhijun,et al.Strata control technology of the fully mechanized face in shallow coal seam close to the above room-and-pillar gob[J].Journal of China Coal Society,2011,36(3):366-370.
[17]解兴智.浅埋煤层房柱式采空区下长壁开采矿压显现特征[J].煤炭学报,2012,37(6):898-902.XIE Xingzhi.Study on the characteristics of strata behavior in shallow seam longwall mining under the room-and-pillar mining goaf[J].Journal of China Coal Society,2012,37(6):898-902.
[18]魏立科,张彬,付兴玉,等.房式采空区下特殊岩梁结构支架工作阻力分析[J].岩石力学与工程学报,2015,34(10):2142-2147.WEI Like,ZHANG Bin,FU Xingyu,et al.Support resistance analysis for special roof structures under room mining goaf[J]. Chinese Journal of Rock Mechanics and Engineering,2015,34(10):2142-2147.
[19] WEI L,QI Q,LI H,et al.A case study of damage energy analysis and an early warning by microseismic monitoring for large area roof caving in shallow depth seams[J].Shock and Vibration,2015,2015:1-9.
[20]徐敬民,朱卫兵,鞠金峰.浅埋房采区下近距离煤层开采动载矿压机理[J].煤炭学报,2017,42(2):500-509.XU Jingmin,ZHU Weibing,JU Jinfeng.Mechanism of dynamic mine pressure occurring below adjacent upper chamber mining goaf with shallow cover depth[J]. Journal of China Coal Society,2017,42(2):500-509.
[2] ZHU Weibing,XU Jingmin,LI Yingchun.Mechanism of the dynamic pressure caused by the instability of upper chamber coal pillars in Shendong coalfield,China[J]. Geosciences Journal,2017,21:729-741.
[3] ZHOU Zilong,CHEN Lu,CAI Xin,et al.Experimental investigation of the progressive failure of multiple pillar-roof system[J].Rock Mechanics and Rock Engineering,2018,51(5):1629-1636.
[4] ZHOU Zilong,CHEN Lu,ZHAO Yuan,et al.Experimental and numerical investigation on the bearing and failure mechanism of multiple pillars under overburden[J]. Rock Mechanics and Rock Engineering,2017,50:995-1010.
[5]周子龙,李夕兵,赵国彦.民窿空区群级联失稳评价[J].自然灾害学报,2007,16(5):91-95.ZHOU Zilong,LI Xibing,ZHAO Guoyan. Evaluation of cascading collapse for private mined zone groups[J]. Journal of Natural Disasters,2007,16(5):91-95.
[6]朱德福,屠世浩,王方田,等.浅埋房式采空区煤柱群稳定性评价[J].煤炭学报,2018,43(2):390-397.ZHU Defu,TU Shihao,WANG Fangtian,et al.Stability evaluation on pillar system of room and pillar mining in goaf at shallow depth seam[J].Journal of China Coal Society,2018,43(2):390-397.
[7]许家林,朱卫兵,鞠金峰.浅埋煤层开采压架类型[J].煤炭学报,2014,39(8):1625-1634.XU Jialin,ZHU Weibing,JU Jinfeng. Supports crushing types in the longwall mining of shallow seams[J].Journal of China Coal Society,2014,39(8):1625-1634.
[8]鞠金峰,许家林.浅埋近距离煤层出煤柱开采压架防治对策[J].采矿与安全工程学报,2013,30(3):323-330.JU Jinfeng,XU Jialin. Prevention measures for support crushing while mining out the upper coal pillar in close distance shallow seams[J]. Journal of Mining&Safety Engineering,2013,30(3):323-330.
[9] XU Jialin,XUAN Dayang,HE Changchun. Innovative backfilling longwall panel layout for better subsidence control effect-separating adjacent subcritical panels with pillars[J]. International Journal of Coal Science&Technology,2014,1(3):297-305.
[10]陈苏社.综采工作面过上层煤集中煤柱动载矿压控制技术[J].煤炭科学技术,2014,42(6):140-143.CHEN Sushe. Dynamic mine strata pressure control technology of full-mechanized coal mining face passing through concentrated coal pillars in above seam[J]. Coal Science and Technology,2014,42(6):140-143.
[11]杨俊哲.浅埋近距离煤层过上覆采空区及煤柱动压防治技术[J].煤炭科学技术,2015,43(6):9-13.YANG Junzhe.Dynamic pressure prevention and control technology of coal mining face with shallow depth and contiguous seams passing through overburden goaf and coal pillars[J]. Coal Science and Technology,2015,43(6):9-13.
[12]李浩荡,杨汉宏,张斌,等.浅埋房式采空区集中煤柱下综采动载控制研究[J].煤炭学报,2015,40(S1):6-11.LI Haodang,YANG Hanhong,ZHANG Bin,et al. Control study of strong strata behaviors during the fully mechanized working face out of concentrated coal pillar in a shallow depth seam in proximity beneath a room mining goaf[J].Journal of China Coal Society,2015,40(S1):6-11.
[13]肖剑儒,李少刚,张彬,等.浅埋深煤层房采区下综采工作面动压控制技术[J].煤炭科学技术,2014,42(10):20-23.XIAO Jianru,LI Shaogang,ZHANG Bin,et al. Control technology of dynamic mine strate pressure of fully-mechanized coal mining face under gob left by room and pillar mining of shallow depth seam[J].Coal Science and Technology,2014,42(10):20-23.
[14] ZHU W,XU J,XU G.Mechanism and control of roof fall and support failure incidents occurring near longwall recovery roadways[J].Journal of the Southern African Institute of Mining and Metallurgy,2017,117:1063-1072.
[15]孟达,王家臣,王进学.房柱式开采上覆岩层破坏与垮落机理[J].煤炭学报,2007,32(6):577-580.MENG Da,WANG Jiachen,WANG Jinxue. Mechanism on the failure and caving of roof strata in pillar and house mining[J].Journal of China Coal Society,2007,32(6):577-580.
[16]屠世浩,窦凤金,万志军,等.浅埋房柱式采空区下近距离煤层综采顶板控制技术[J].煤炭学报,2011,36(3):366-370.TU Shihao,DOU Fengjin,WAN Zhijun,et al.Strata control technology of the fully mechanized face in shallow coal seam close to the above room-and-pillar gob[J].Journal of China Coal Society,2011,36(3):366-370.
[17]解兴智.浅埋煤层房柱式采空区下长壁开采矿压显现特征[J].煤炭学报,2012,37(6):898-902.XIE Xingzhi.Study on the characteristics of strata behavior in shallow seam longwall mining under the room-and-pillar mining goaf[J].Journal of China Coal Society,2012,37(6):898-902.
[18]魏立科,张彬,付兴玉,等.房式采空区下特殊岩梁结构支架工作阻力分析[J].岩石力学与工程学报,2015,34(10):2142-2147.WEI Like,ZHANG Bin,FU Xingyu,et al.Support resistance analysis for special roof structures under room mining goaf[J]. Chinese Journal of Rock Mechanics and Engineering,2015,34(10):2142-2147.
[19] WEI L,QI Q,LI H,et al.A case study of damage energy analysis and an early warning by microseismic monitoring for large area roof caving in shallow depth seams[J].Shock and Vibration,2015,2015:1-9.
[20]徐敬民,朱卫兵,鞠金峰.浅埋房采区下近距离煤层开采动载矿压机理[J].煤炭学报,2017,42(2):500-509.XU Jingmin,ZHU Weibing,JU Jinfeng.Mechanism of dynamic mine pressure occurring below adjacent upper chamber mining goaf with shallow cover depth[J]. Journal of China Coal Society,2017,42(2):500-509.
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