岩层采动裂隙分布在绿色开采中的应用

岩层采动裂隙分布的研究与水体下和承压水上采煤、卸压瓦斯抽放、离层区充填与开采沉陷控制等工程问题紧密相关，通过试验与理论分析，对岩层移动过程中的覆岩采动裂隙动态发育特征及其影响因素进行了深入研究，结果证明：覆岩关键层对离层及裂隙的产生、发展与时空分布起控制作用．基于关键层破断前后采动裂隙动态发育特性与差异，提出了“覆岩离层分区隔离充填减沉法”和卸压瓦斯抽放的“O”形圈理论，并分别应用于我国不迁村采煤试验和卸压煤层气开采实践。     

采动覆岩破断裂隙的贯通度研究

为了判定采场隔水关键层和计算导水裂隙带高度,进行了覆岩采动导水裂隙分布特征的相似模拟实验和力学分析.提出了破断裂隙贯通度的概念和计算公式.试验结果表明,采场覆岩裂隙带上位岩层的回转变形空间较小,且由于岩层刚度和厚度的差异,薄岩层会完全破断;但坚硬厚岩层破断裂隙未贯通,没有形成竖向"导水、导气"裂隙.为了描述岩层的破断程度及破断裂隙导水能力的强弱岩层破断裂隙的贯通度随其下自由空间的增大而增大,且存在自由空间阀值,大于其阀值时则增加缓慢并趋于1;随岩层厚度增大,起裂时岩层破断裂缝的张开角度减小;岩层破断裂隙的贯通度随裂纹尖端临界张开位移的增大而呈线性减小,随岩层周期破断距的增大也呈近似线性减小.     

基于地表点下沉阶段特征的覆岩裂隙带高度演化

煤炭开采引起覆岩破断及地表下沉,覆岩及地表运移规律可反映裂隙带高度的动态演化过程,因地表下沉滞后于煤炭开采,采空区封闭后,长期压实作用导致裂隙带高度较采动期间有所降低.基于地表点下沉速度的阶段特征将裂隙带高度的演化全程分为2个阶段,第1阶段裂隙带发育对应岩层破断逐步向上传递的过程,第2阶段裂隙带高度降低对应离层及裂隙闭合、断裂岩层受压后变形回弹及破碎岩体自然压实的过程,针对不同阶段裂隙带高度演化开展了试验研究和理论推导,揭示了不同阶段裂隙带高度的演化特征及影响机制,并结合同忻煤矿和太平煤矿实测结果进行了验证.研究结果表明,关键层的控制作用使得裂隙带高度阶段性增长,关键层最终破断层位及其上方部分岩层的岩性特征决定了第1阶段裂隙带发育高度,第2阶段裂隙带高度由第1阶段结束时裂隙带高度及垮落带高度、不同状态下的垮落带碎胀系数及地表动态下沉结束后的下沉量决定.研究可为废弃采空区卸压瓦斯地面抽采钻井结构设计及煤矿地下水库极限库容计算提供参考.     

采场覆岩中复合关键层的形成条件与判别方法

在采场覆岩运动中起主要控制作用的岩层为关键层，而有时关键层是由2层或2层以上岩层形成的复合岩层所组成，我们称其为复合关键层．本文在深入揭示复合岩层形成机理的基础上，给出了形成复合岩层的力学条件与数学表达式，进而建立了采场覆岩中复合关键层的判别方法，并编写了复合关键层的判别程序．实例分析表明，复合关键层在岩层运动中是客观存在的，比同组岩层分开后的单一岩层的控制作用的线性叠加要大得多．本项研究是岩层控制的关键层理论研究的深入和发展，将有力促进岩层控制理论和技术的发展．     

神东特殊保水开采煤层条带充填覆岩隔水层稳定性判据

神东矿区特殊保水开采覆岩隔水层中剩余基岩具有结构承载特性,其上方黏性土层具有封堵导水裂隙功能.依据岩层控制理论,建立神东特殊保水开采煤层条带充填覆岩结构隔水层力学模型.采用应力和应变作为衡量覆岩结构隔水层及上方黏性土层破断导水的指标,推导结构隔水层及上方黏性土层稳定性力学判据,分析条带充填覆岩隔水层稳定性影响因素.结果表明:结构隔水层上作用的最大拉应力随其厚度、充填条带宽度、弹性地基系数的增大而减小;随覆岩含水层水压的增大而增大;随覆岩垮落角的增大而先快速增大后趋于平缓.黏性土层产生的最大拉应变随其厚度的增大而增大;随其弹性模量的减小而快速增大.充分采动后,结构隔水层上作用的最大拉应力随工作面推进距离的增大而趋于稳定.     

覆岩宏观支撑结构演化过程与特征

针对近水平煤层开采采场覆岩支撑结构的宏观特征,构建了覆岩宏观支撑结构的板-壳组合演化模型,分析了覆岩宏观支撑结构的形成-演化过程及其基本特征,在此基础上建立梁-拱力学模型,得到了覆岩宏观支撑结构中壳体形态、关键层悬露长度以及"充分采动"时采空区几何特征的计算方程.结果表明:近水平煤层开采采场覆岩宏观支撑结构的演化过程主要表现为倾向巷道→见方→走向巷道.在关键层影响下,覆岩宏观支撑结构整体呈现为板-壳组合的阶梯状结构,水平剖面形态为圆角矩形,倾向和走向剖面形态为梁-拱组合.如在采空区见方之前关键层已破断垮落,则在采空区见方时会伴随产生覆岩裂隙带高度、煤壁支承压力达最大值等"充分采动"现象;如在采空区见方时关键层未破断垮落,则在工作面推进距离与工作面长度之比为1～3时,也可能出现"充分采动"现象.研究结果得到了杨柳煤矿10414工作面实测数据的验证.     

采动覆岩中关键层的破断规律研究

介绍了采动覆岩中关键层上的载荷和支承压力分布随覆岩分层的几何和力学特性变化的规律,具体分析了关键层内的极限应力与软弱夹层厚度及坚硬岩层厚度的关系,并由关键层断裂的先后次序,说明了主关键层和亚关键层的辩证关系,并且揭示了坚硬岩层与坚硬岩层之间的复合效应．     

覆岩关键层位置的判别方法

建立了判别覆岩中关键层位置的实用方法,并编制了相应的计算机软件ＫＳＰＢ。首次 相邻两层硬岩同步破断的理论判别式,并就相邻两层破断顺序的影响因素进行分析,结果表明,两硬岩层厚度、间距以及上层硬岩所承受的载荷大小是影响相邻层硬岩民支破断顺序的主要因素。     

特厚煤层坚硬覆岩柱壳结构特征模型及应用

以大同矿区同忻煤矿石炭系坚硬覆岩特厚煤层开采为工程背景,基于关键层理论分析了同忻矿3-5#煤层特厚煤层综放开采坚硬覆岩的破断特征和采场覆岩结构特征;应用弹性板理论,建立了大空间采场坚硬覆岩柱壳结构力学模型和数学模型.研究表明:坚硬覆岩柱壳结构模型,较好地揭示了同忻矿8105,8106等工作面开采过程中产生大小周期来压、采动影响范围大、易产生冲击载荷等特殊矿压现象的机理.     

基于采空区压实效应的工作面开采全过程模拟

为探究孤岛工作面开采时覆岩破断、运移和矿压显现规律,利用FLAC~(3D) Fish语言开发了数值算法,基于采空区压实理论和双屈服模型,提出一种孤岛工作面推进过程中覆岩破断演化、垮落带岩体的压实效应和采动静载、动载响应数值模拟方法.采用该方法对朝阳煤矿3108孤岛工作面采动全过程及其动静载演化机制进行了数值模拟,所得结果与现场实际具有较好的一致性.结果表明:由于两侧采空区工作面长度较小(70 m),开采后覆岩垮落不充分,垮落带和裂隙带演化高度有限,约为30.98和66.91 m;动载主要来源于顶板破断释放能量,震源和覆岩裂隙带演化的最大高度基本一致,其震源包络线与裂隙带的发育范围吻合度较高.     

巷道底板承压水突水评价方法研究

华北石炭二叠纪聚煤区是中国最重要的煤炭生产基地,区内众多煤矿皆受煤系底部奥陶系灰岩承压水威胁。针对当前煤矿巷道底板承压水突水评价方法存在的局限和不足,探索研究巷道底板承压水突水评价方法。现行评价方法岩梁法的理论计算前提主要包括：底板隔水层简化为两端固支梁;在岩梁弯矩最大处,底板隔水岩层承受的拉应力超过抗拉强度,岩层拉裂破坏;忽略孔隙水压力对岩石破坏的影响,计算隔水层厚度时抗拉强度取底板隔水层的平均值。事故数据及研究分析表明岩梁法计算假设存在不合理之处,与实际工况有较大偏差。基于对常见矩形巷道围岩应力分布特征的分析,结合巷道实际工况,摒弃底板隔水岩层弯拉破坏模式,提出隔水岩层剪切破坏模式,建立巷道底板承压水突水破坏岩柱模型;基于所建立的岩柱模型,利用极限平衡理论,综合考虑孔隙水压力对岩石破坏的影响,推导底板隔水层承受最大水压的计算评价方法。结果表明：最大水压与隔水层厚度、隔水层平均容重、抗剪强度参数、孔隙水压力系数和巷道宽度直接相关,最大水压与隔水层厚度呈指数函数关系。文中所提评价方法的计算结果与实测吻合,证明该方法合理有效。所提方法也能为地下工程其他专业领域类似的承压水突水问题研究提供借鉴。     

Breaking process and mining stress evolution characteristics of a high-position hard and thick stratum

Based on the boundary support conditions of overlying high-position,hard and thick strata,a Winkler foundation beam mechanical model was built.Computational expressions for the characteristics and position of the bending moment for high-position,hard and thick strata were constructed by theoretical analysis,and the initial breaking position of high-position,hard and thick strata was also analyzed.The breaking process and evolution law of mining stress in high-position,hard and thick strata were studied by similar material simulation tests.Studies show that:due to the foundation deformation effect of the lower strata,the initial break position in high-position,hard thick layers is in the middle of goaf;vertical tension fractures first occur under the middle surface,then tilt tension fractures form at both sides and a non-uniform thickness of the fracture structure forms and produces subsidence deformation;behind the coal wall tilt fractures extend and eventually complete the migration.Mining stress produces obvious changes before and after the breakage of the high,hard and thick stratum;high stress concentration forms in front of the coal wall before breakage and fracture stress concentration significantly reduces after migration.Coal seam mining under high-position,hard thick strata can easily induce dynamic phenomena.     

Mechanism of rock burst caused by fracture of key strata during irregular working face mining and its prevention methods

To study the occurrence mechanism of rock burst during mining the irregular working face, the study took irregular panel 7447 near fault tectonic as an engineering background. The spatial fracture characteristic of overlying strata was analyzed by Winkler elastic foundation beam theory. Furthermore, the influence law of panel width to suspended width and limit breaking span of key strata were also analyzed by thin plate theory. Through micro-seismic monitoring, theoretical analysis, numerical simulation and working resistance of support of field measurement, this study investigated the fracture characteristic of overlying strata and mechanism of rock burst in irregular working face. The results show that the fracture characteristic of overlying strata shows a spatial trapezoid structure, with the main roof being as an undersurface. The fracture form changes from vertical “O-X” type to transverse “O-X” type with the increase of trapezoidal height. From the narrow mining face to the wide mining face, the suspended width of key strata is greater than its limit breaking width, and a strong dynamic load is produced by the fracture of key strata. The numerical simulation and micro-seismic monitoring results show that the initial fracture position of key strata is close to tailgate 7447. Also there is a high static load caused by fault tectonic. The dynamic and static combined load induce rock burst. Accordingly, a cooperative control technology was proposed, which can weaken dynamic load by hard roof directional hydraulic fracture and enhance surrounding rock by supporting system.     

Analysis of Water Insulating Effect of Compound Water-Resisting Key Strata in Deep Mining

The problem of water preservation in mining and the prevention of water-bursts has been one of the more important issues in deep mining. Based on the concept of water-resisting key strata, the mechanics model of the key strata is established given the structural characteristics and the mechanical properties of the roof rock layers of the working face in a particular coal mine. Four other models were derived from this model by re-arranging the order of the layers in the key strata. The distribution characteristics of stress, deformation, pore pressure and the flow vector of all the models are computed using the analytical module of fluid-structure interaction in the FLAC software and the corre- sponding risks of a water-burst are analyzed. The results indicate that the water-insulating ability of the key strata is related to the arrangement of soft and hard rocks. The water-insulating ability of the compound water-resisting key strata （CWKS） with a hard-hard-soft-hard-soft compounding order is the best under the five given simulated conditions.     

Pore structure characteristics of the relative water-resisting layer on the top of the Ordovician in Longgu Coal Mine

In order to study the permeability and water-resisting ability of the strata on the top of the Ordovician in Longgu Coal Mine, this paper tested the permeability and porosity of the strata, investigated the fracture and pore structure features of the strata, and identified the main channels which govern the permeability and water-resisting ability of the strata. The permeability of the upper, central and lower strata shows as 2.0504 × 10⁻³–2.782762 × 10⁻³, 4.1092 × 10⁻³–7.3387 × 10⁻³ and 2.0891 × 10⁻³–3.2705 × 10⁻³ μm², respectively, and porosity of that is 0.6786–0.9197%, 0.3109–0.3951% and 0.9829–1.8655%, respectively. The results indicate that: (1) the main channels of the relative water-resisting layer are the pore throats with a diameter more than 6 μm; (2) the major proportion of pore throats in the vertical flow channel and the permeability first increases and then sharply decreases; (3) the fractures occurring from the top to 20 m in depth of the strata were filled and there occurred almost no fracture under the depth of 40 m; and (4) the ratio of turning point of the main flow channel in the strata on top of Ordovician can be used to confirm the thickness of filled water-resisting layers.     

瞬变电磁法在探测第四系底部砂层和黏土层分布中的应用

煤层顶板的砂层富水区和黏土隔水层分布规律的研究,对缩小防水煤柱、提高开采上限等有着至关重要的影响.探明直接覆盖在煤系地层之上的第四系底部砂层和黏土层的分布,可以有效地指导煤矿的防治水工作.瞬变电磁法近年广泛应用于煤矿富水区的探查,与其他方法相比,它具有低阻地质体反映灵敏,纵横向分辨率高,勘探深度大等优势.本文结合在山东...     

Investigation on fracture models and ground pressure distribution of thick hard rock strata including weak interlayer

Dynamic disasters, such as rock burst due to the breaking of large area stiff roof strata, are known to occur in the hard rock strata of coal mines. In this paper, mechanical models of the fracturing processes of thick hard rock strata were established based on the thick plate theory and numerical simulations. The results demonstrated that, based on the fracture characteristics of the thick hard rock strata, four fracture models could be analyzed in detail, and the corresponding theoretical failure criteria were determined in detail. In addition, the influence of weak interlayer position on the fracture models and ground pressure of rock strata is deeply analyzed, and six numerical simulation schemes have been implemented. The results showed that the working face pressure caused by the independent movement of the lower layer is relatively low. The different fracture type of the thick hard rock strata had different demands on the working resistance of the hydraulic powered supports. The working resistance of the hydraulic powered supports required by the stratified movements was lower than that of the non-stratified movements.     

Relationship between water inrush from coal seam floors and main roof weighting

A water-resistant key strata model of a goaf floor prior to main roof weighting was developed to explore the relationship between water inrush from the floor and main roof weighting. The stress distribution,broken characteristics, and the risk area for water inrush of the water-resistant key strata were analysed using elastic thin plate theory. The formula of the maximum water pressure tolerated by the waterresistant key strata was deduced. The effects of the caved load of the goaf, the goaf size prior to main roof weighting, the advancing distance of the workface or weighting step, and the thickness of the waterresistant key strata on the breaking and instability of the water-resistant key strata were analysed.The results indicate that the water inrush from the floor can be predicted and prevented by controlling the initial or periodic weighting step with measures such as artificial forced caving, thus achieving safe mining conditions above confined aquifers. The findings provide an important theoretical basis for determining water inrush from the floor when mining above confined aquifers.     

朱集矿采动上覆岩层活动演化规律相似模拟研究

以朱集矿工作面开采技术条件为背景,建立了工程地质模型,采用相似模拟实验,研究了工作面开采后,上覆岩层变形移动及裂隙分布演化特征,获得了采动岩层破断垮落及位移特征参数,以及与工作面推进度的相互作用关系,为留巷位置的合理确定、上行开采可行性等工程实践提供了科学依据。