煤矿结构充填开采“充填体--直接顶”复合承载结构稳定性研究.pdf

万方数据 万方数据 太原理工大学博士研究生学位论文 I 煤矿结构充填开采“充填体-直接顶”复合承载结构稳定性研究 摘 要 充填开采作为一种绿色开采方法，可有效控制矿山开采引起的覆岩破 坏和地表沉陷，具有回采率高和生态环保等优势，是实现“三下”压煤等 遗煤资源安全高效开采的重要手段。然而，目前充填开采并没有被煤矿广 泛推广，究其本质原因还是成本较高。充填原材料需求量巨大、材料输送 工作量大、充填工艺复杂且效率较低是造成充填成本居高不下的主要原因。 同时，大量充填材料占据着采空区，使煤矿面临地下空间被大量浪费的窘 境与挑战。针对煤矿充填开采面临的这些问题与挑战，太原理工大学冯国 瑞教授提出了结构充填开采的思想与理念，并进行了相应的研究攻关。结 构充填开采通过因地制宜的 “固废充填材料” 、 科学布设的 “结构充填体” 、 成套研发的“结构充填工艺及装备”来适应“构造应力和采动应力”，并 最大化地构建出“可利用的地下空间”。通过构建“充填体-直接顶”复合 承载结构，最大程度地提高充填体的承载能力和发挥直接顶的自承载能力， 降低充填开采成本，并为后期开发和利用煤矿地下空间提供便利条件，有 效促进充填开采在煤矿领域中的进一步推广。 鉴于此，本文对结构充填开采“充填体-直接顶”复合承载结构的稳定 性进行了系统研究。通过室内力学实验分析了无侧限充填体和加筋充填柱 的破坏特征和承载机理，为结构充填体力学参数的取值提供依据；构建了 “充填体-直接顶”复合承载结构的力学模型，解析了条带结构充填和柱式 结构充填的直接顶变形特征，得到了直接顶发生破断的临界充填间距；通 过数值模拟试验分析了不同因素对“充填体-直接顶”复合承载结构稳定性 的影响规律，确定了各因素的合理取值；通过相似模拟试验获得了结构充 万方数据 太原理工大学博士研究生学位论文 II 填开采过程中覆岩结构和采场应力的变化特征，验证了“充填体-直接顶” 复合承载结构的承载效果。 主要研究内容与结论如下 1 开展了无侧限充填体标准尺寸150mm 150mm 150mm和大尺寸 800mm 800mm 800mm立方体试件的单轴压缩实验，发现了无侧限充填 体试件内部存在核心承载区。在单轴压缩过程中，核心承载区由弹性核区 逐渐演化成塑性残余承载区。无侧限充填体表面的起始破坏应力约为单轴 抗压强度的 0.28 倍，核心承载区的起始破坏应力约为单轴抗压强度的 0.64 倍。核心承载区的最大承载能力约为单轴抗压强度的 2.00 倍，残余承载力 大于单轴抗压强度的 0.80 倍。试件内部不同位置的应力曲线和变形曲线可 分为四个阶段缓慢增长阶段、快速增长阶段、快速下降阶段和缓慢下降 阶段，三个阶段转折点可分别作为试件的破坏前兆点、临界失稳点和残余 承载/变形起始点。 2 开展了 800mm 800mm 1600mm 大尺寸加筋充填柱的单轴压缩实 验，通过与无筋充填柱对比发现，环向钢筋限制了竖向裂隙的产生与扩展， 提高了充填柱的抗剪强度，在试件内部形成了有效承载区。有效承载区的 存在提高了加筋充填柱的抗压承载力和延性，有效地防止了充填柱的突然 失稳。研究同时发现内部应力的差异是充填柱失稳的根本原因，内部变形 的差异是充填柱失稳的直接原因，结构充填开采中充填柱的稳定性可以通 过监测其内部应力和变形来判定。 3 建立了“充填条带-直接顶”复合承载结构温克尔弹性地基上的有 限长梁力学模型，运用初始参数法解析得到了条带结构充填的直接顶变形 方程。结合新阳矿工程地质条件，得到了当充填体强度为 10MPa、充填率 为 51时，直接顶发生破断时的临界充填间距为 11.95m。通过 FLAC3D数 值模拟研究了充填间距、充填条带宽度和欠接顶量对“充填条带-直接顶” 万方数据 太原理工大学博士研究生学位论文 III 复合承载结构稳定性的影响，结果表明当充填条带间距大于 5m 时，空顶 区中心的直接顶发生拉伸破坏，充填条带的边缘发生剪切破坏；当充填条 带宽度大于 4m 时，充填条带边缘发生应力集中，使充填条带顶角发生剪切 破坏；当欠接顶量为 200mm 时，采空区边缘直接顶与上覆岩层产生离层； 综合分析得到条带结构充填开采的合理充填间距为 25m，充填条带的合理 宽度在 2m 左右，欠接顶量应不大于 150mm。通过相似模拟试验验证了 当充填条带宽度和间距均为 2.5m 时，条带结构充填开采覆岩结构稳定性良 好，直接顶承载能力明显增强，形成了稳定的“充填条带-直接顶”复合承 载结构。 4 建立了柱式结构充填“充填柱-直接顶”复合承载结构温克尔弹性 地基上的中厚板力学模型，运用胡海昌理论分别解析得到了矩形中厚板模 型和圆形中厚板模型的直接顶变形方程。结合新阳矿工程地质条件，得到 了当充填体强度为 20MPa、充填率为 25.45时，直接顶发生破断的临界充 填间距为 3.23m。通过 FLAC3D数值模拟研究了充填间距、充填柱宽度和欠 接顶量对“充填柱-直接顶”复合承载结构稳定性的影响，结果表明当充 填柱间距大于 3m 时，空顶区中心的直接顶会发生拉伸破坏，充填柱的边缘 会发生剪切破坏；当充填柱宽度大于 3m 时，充填体边缘发生应力集中，使 充填柱顶角发生剪切破坏；当欠接顶量为 150mm 时，采空区中部顶板和充 填柱破坏严重，“充填柱-直接顶”复合承载结构失去稳定性；综合分析得 到柱式结构充填的合理充填间距为 13m，充填柱的合理宽度在 2m 左右， 欠接顶量应不大于 100mm。通过相似模拟试验验证了当充填柱宽度和间 距均为 2.5m 时，柱式结构充填开采覆岩结构稳定性良好，直接顶承载能力 明显增强，形成了稳定的“充填柱-直接顶”复合承载结构。 关键词 结构充填开采，无侧限充填体，充填柱，直接顶，复合承载结构 万方数据 太原理工大学博士研究生学位论文 IV 万方数据 太原理工大学博士研究生学位论文 V RESEARCH ON THE STABILITY OF “BACKFILL BODY - IMMEDIATE ROOF“ COMBINED BEARING STRUCTURE IN CONTRUCTIONAL BACKFILL COAL MINING ABSTRACT Backfill mining is an important green mining for controlling overburden failure and surface subsidence because of its advantages of high recovery rate and protecting environment. However, backfill mining is not widely used in coal mine at present, the essential reason is the high cost, which is caused by that the volume of backfill materials is large, the workload of material transportation is large, the backfill technology is complex and inefficient. At the same time, backfill mining is also facing the challenge that a lot of underground space is wasted since a large number of backfill materials occupy the goaf of coal seam. Professor Feng Guorui of Taiyuan University of Technology puts forward the idea of constructional backfill mining CBM in view of the problems and challenges. CBM is a green mining using the “backfill material of solid waste recycling“ adapted to local conditions, the “constructional backfill body“ scientifically analyzed, and the “constructural backfill technology and equipment“ which are complete researched and developmented to adapt to the “tectonic stress and mining induced stress“ and maximize using the “available underground space“. Through establish a stable composite bearing structure of “backfill body-immediate roof“, CBM can improve the bearing capacity of backfill body and rt the maximum self-bearing capacity of immediate roof, reduce the cost of backfill coal mining, and provide convenient conditions for the development and utilization the 万方数据 太原理工大学博士研究生学位论文 VI underground space of coal mine, which can effectively promote the further development of backfill mining in the field of coal mine. In view of this, the stability of the “backfill body-immediate roof“ composite bearing structure is studied in this paper. The failure characteristics and bearing mechanism of unconfined backfill body and reinforced backfill column are analyzed through laboratory mechanical experiments, which provide the basis for the selection of mechanical parameters of constructional backfill body. The deation characteristics of immediate roof under strip and column constructional backfill mining are analyzed by establishing the mechanical model of “backfill body - immediate roof“ composite bearing structure, and the maximum backfill spacing is obtained according to the immediate roof breaking. The influence law of different factors on the stability of “backfill body - immediate roof“ composite bearing structure is analyzed by numerical simulation experiment, and reasonable values of the factors are obtained. The control effect on the pressure appearance and strata movement of CBM is verified by similar simulation test, which verified the bearing effect of “backfill body - immediate roof“ composite bearing structure. The main research contents and conclusions are as follows 1 The uniaxial compression experiments of cube specimens of standard size 150 mm 150 mm 150 mm and large size 800 mm 800 mm 800 mm show that there is a core bearing area in the unconfined backfill body. In the compression process, the core bearing area evolves from elastic core area to residual plastic bearing area gradually. The start breaking stress of specimen surface is about 28 of uniaxial compressive strength UCS. The start breaking stress of core bearing area is about 64 of UCS. The maximum bearing capacity of the core bearing area is about 2 times of the UCS. The residual bearing capacity of the core bearing area is larger than 80 of the UCS of cubic specimens. The internal stress curves and internal deation curves of unconfined backfill body are divided into four stages slow growth stage, rapid 万方数据 太原理工大学博士研究生学位论文 VII growth stage, rapid decline stage and slow decline stage. There are three turning points of the four stages that can be used as the failure precursor piont, critical instability point and starting point of residual bearing capacity or deation, respectively. 2 By comparing with the backfill column without stirrups, it is found that the generation and expansion of vertical cracks is limited and the shear strength of backfill column is improved by stirrups, and an effective bearing area is ed in the middle of the 800mm 800mm 1600 mm backfill column with stirrups in the failure process under uniaxial compression. The effective bearing area improves the compressive bearing capacity and ductility of backfill column, and prevents the sudden instability of backfill column effectively. It shows that the difference of internal stress is the fundamental reason for the instability of backfill columns, and the difference of internal deation is the direct reason for the instability of backfill columns. The stability of backfill columns in constructional backfill engineering can be monitored by internal stress and deation. 3 Combining elastic foundation theory, the finite beam model on Winkler elastic foundation of “backfill strip- immediate roof“ composite bearing structure is established. The deation characteristics of the immediate roof filled with backfill strip are analyzed through the initial parameter . According to the engineering geological conditions of Xinyang Mine, the critical spacing of strip constructional backfill when immediate roof is broken in Xinyang Mine is 11.95 m with the strength of backfill body is 10 MPa and backfill rate is 51. The effects of backfill spacing, backfill strip width and lacking distance of roof-contact on the stability of composite bearing structure are studied by FLAC3D numerical simulation. The results show that it will cause tensile failure in the middle of the goaf and shear failure at the edge of the backfill strip when the spacing of backfill strips is larger than 5m. The stress concentration will occur at the edge of backfill strip when the width of backfill 万方数据 太原理工大学博士研究生学位论文 VIII strip is more than 4 m, which will cause the shear failure of the top angle of backfill strip. The immediate roof will separate from the overlying strata at the edge of the goaf when the lacking distance of roof-contact is 200 mm. Comprehensive analysis shows that the reasonable spacing of backfill strip is 2 5m, the optimum width of backfill strip is ahout 2 m and the lacking distance of roof-contact should be not more than 150mm. The similar simulation test shows that the strip costructional backfill has good structural stability and the bearing capacity of the immediate roof is obviously enhanced in Xinyang Mine when the width and spacing of backfill strips are 2.5m. The stable composite bearing structure of “backfill strip - immediate roof“ is ed. 4 Combining elastic foundation theory, the medium thick plate model of Winkler elastic foundation of “backfill column-immediate roof“ composite bearing structure is established. The deation characteristics of the immediate roof filled with backfill column are analyzed based on the Hu Haichangs theory. According to the engineering geological conditions of Xinyang Mine, the critical spacing of column constructional backfill when immediate roof is broken in Xinyang Mine is 3.23 m with the strength of backfill body is 20 MPa and backfill rate is 25.45. Further more, the effects of backfill spacing, backfill column width and lacking distance of roof-contact on the stability of composite bearing structure are studied by FLAC3D numerical simulation. The results show that it will cause tensile failure in the middle of the goaf and shear failure at the edge of the backfill column when the spacing of backfill columns is larger than 3m. The stress concentration will occur at the edge of backfill column when the width of backfill column is more than 3 m, which will cause the shear failure of the top angle of backfill column. The roof and backfill column in middle of goaf are seriously damaged, and the composite bearing structure of “backfill column and immediate roof” loses stability when the lacking distance of roof-contact is 150 mm. Comprehensive analysis shows that the reasonable spacing of backfill column is 1 3m, the optimum width of 万方数据 太原理工大学博士研究生学位论文 IX backfill column is about 2m and the lacking distance of roof-contact should be not more than 100mm. The similar simulation test shows that the column costructional backfill has good structural stability and the bearing capacity of the immediate roof is obviously enhanced in Xinyang Mine when the width and spacing of backfill columns are 2.5m. The stable composite bearing structure of “backfill column - immediate roof“ is ed. KEY WORDS constructional backfill mining, unconfined backfill body, backfill column, immediate roof, composite bearing structure 万方数据 太原理工大学博士研究生学位论文 X 万方数据 太原理工大学博士研究生学位论文 i 目 录 摘 要 ........................................................................................................................................... I ABSTRACT .............................................................................................................................. V 目 录 ........................................................................................................................................... i 第一章 绪论 .............................................................................................................................. 1 1.1 研究背景与意义 ......................................................................................................... 1 1.2 国内外研究现状 ......................................................................................................... 2 1.2.1 煤矿充填开采技术方法研究现状 .................................................................. 2 1.2.2 胶结膏体充填材料力学性能研究现状 .......................................................... 6 1.2.3 煤矿充填开采覆岩移动特征研究现状 ........................................................ 11 1.3 研究内容及方法 ....................................................................................................... 14 1.4 技术路线图 ............................................................................................................... 15 第二章 结构充填开采基础理论与关键技术 ........................................................................ 17 2.1 压煤资源开采地下空间开发利用构想 ................................................................... 17 2.1.1 城市下压煤充填开采建设地下综合体 ........................................................ 17 2.1.2 村镇、农田下压煤充填开采建设地下农业基地 ........................................ 18 2.1.3 铁路公路、水体下压煤充填开采建设地下储库 ..................................... 19 2.2 结构充填开采基础理论 ........................................................................................... 20 2.2.1 结构充填开采的内涵 .................................................................................... 20 2.2.2 结构充填开采的目标 .................................................................................... 21 2.2.3 结构充填开采的关键位置 ............................................................................ 22 2.3 结构充填开采的关键技术 ....................................................................................... 24 2.3.1 开发新型固废充填材料 ................................................................................ 24 2.3.2 构建“充填体-直接顶”复合承载结构 ...................................................... 25 2.3.3 研发井下一体化结构充填系统 .................................................................... 27 2.4 本章小结 ................................................................................................................... 29 第三章 无侧限充填体单轴压缩破坏机理研究 .................................................................... 31 万方数据 太原理工大学博士研究生学位论文 ii 3.1 实验方案 ................................................................................................................... 31 3.1.1 实验材料 ........................................................................................................ 31 3.1.2 标准立方体试件实验方案 ............................................................................ 32 3.1.3 大尺寸立方体试件实验方案 ........................................................................ 33 3.2 标准立方体试件单轴压缩破坏机理 ....................................................................... 35 3.2.1 宏观变化特征 .....................................................................