采矿数值模拟研究中上部边界条件确定的探讨

采用UDEC数值模拟计算,对岩层移动模拟研究中如何确定简化模型上部边界条件进行了研究.结果表明,当模型中存在主关键层时,将主关键层以上的岩层自重简化为均布荷载加在模型上边界,当模型中不存在主关键层时,将导水裂隙带以上的岩层自重简化为均布荷载加在模型上边界,均对老顶的跨落距、老顶上垂直应力分布和老顶的位移没有显著影响,因此,可以将主关键层以上或导水裂缝带以上的岩层自重简化为均布载荷作为上部边界条件加在模型上边界.     

底板岩体结构稳定性与底板突水关系的研究

将煤层底板至含水层之间承载能力最大的一层岩层看作底板关键层，从而将采场底板突水的研究转化为对底板关键层破断机制的研究，将关键层看作受水压等均布载荷作用的弹性薄板，得出了它的极限破断跨距公式，并提出了利用已知突水事故资料反演预测岩体强度的方法，提高了理论计算精度。最后，分析了底板关键层破断后的块体平衡条件，解释了突水点的分布特点与突水时产生的底鼓现象。     

关键层对急斜下保护层开采保护作用的影响

以某矿多煤层下保护层急倾斜俯伪斜工作面为例,确定了沿工作面伪斜方向顶板硬岩层承受的栽荷和充填体的支撑栽荷的表达式.基于关键层理论和有限元数值模拟方法,确定了下保护煤层开采后上覆岩层中的关键层的位置及其破断距;得出了急倾斜煤层开采后受关键层影响下的上覆岩层移动特点和破坏形态;分析了关键层对保护层开采保护范围的影响.研究表明,距下保护层K6煤层17 m的硅质石灰岩为上覆岩层中的关键层,其破断距为30 m左右;关键层破断之前,关键层上部的被保护层卸压并不明显;关键层破断以后,保护层的保护作用逐渐明显;且被保护层的瓦斯涌出规律与关键层破断距成周期变化,倾斜上部瓦斯得到充分释放,而倾斜下部由于冒落矸石的充填导致岩层变形较小,瓦斯不能充分释放,使保护范围在倾向上部比下部大.     

煤矿绿色开采技术研究的理论新平台--评《岩层控制的关键层理论》

由钱鸣高、缪协兴、许家林、茅献彪等撰写的《岩层控制的关键层理论》一书已由中国矿业大学出版社于2003年出版．该书全面系统总结了岩层控制的关键层理论与实践成果．内容包括：关键层理论的提出、基本概念及判别方法；在理论上阐明了关键层上的载荷分布规律、关键层的破断规律及其复合效应；同时     

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.     

浅埋煤层群开采顶板双关键层结构及支护阻力研究

采用现场实测、物理相似模拟和理论分析方法,分析了浅埋煤层群间隔岩层双关键层的形成条件、双关键层结构稳定性和支架载荷计算方法.基于对神府矿区4-2与5-2煤层开采的实测发现,浅埋煤层群较单一煤层开采周期来压步距缩短25%,来压强度增加15%～22%.物理相似模拟表明,间隔岩层存在双关键层结构时,直接顶以"短悬臂梁"形式周期破断,间隔岩层下位关键层与上位关键层分别形成铰接结构,上煤层已垮落的顶板形成活化的砌体梁结构.根据顶板结构组合形态,可将浅埋煤层群双关键结构分为"台阶-砌体-砌体"结构、"台阶-台阶-砌体"结构和"砌体-砌体-砌体"结构.双关键层结构同步与非同步破断运动形成大、小周期来压现象.通过建立的"台阶-砌体-砌体"结构力学模型,给出了动、静载荷作用下工作面支护阻力计算方法.     

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。     

顶板隔水层关键层耦合作用规律研究

在煤矿开采过程中，如果覆岩裂隙扩展至贯穿隔水层，则会诱发地下水或地表水大量涌向采场，导致煤矿淹井事故．利用RFPA^2D-Flow软件建立了隔水层关键层耦合的采场推进模型，计算并分析了裂隙场的发育和分布，绘制了顶板水渗流量曲线．讨论了与裂隙发育密切相关的覆岩支承压力与中间岩层厚度、关键层厚度及破断闻的关系．结果表明：关键层未破断时，中问岩层厚度对隔水层裂隙发育作用不明显；厚关键层对隔水层能起较好的保护作用．     

双关键层跨煤组远程卸压增透效应试验研究

以潘二煤矿11223工作面远程卸压4~#煤为研究背景,采用物理模拟、FLAC~(3D)流固耦合模拟及现场工程实测相结合的方法,对远程被保护层4~#煤卸压增透区分布特征及关键层破断影响卸压瓦斯抽采效果机制进行分析.结果表明:1)卸压瓦斯抽采量极值点间距与上位关键层周期断裂步距吻合,而下位关键层破断对卸压瓦斯抽采没有直接影响,上位关键层周期断裂步距对远程卸压瓦斯抽采峰位具有一定预测作用;2)经压实变形后,被保护层膨胀变形和渗透率在煤层倾斜方向呈双峰形态,其量值为在中下部最大,中上部次之,中部最小;3) 4~#煤实测膨胀变形达到1.26%,卸压瓦斯抽采率为69.59%,煤层渗透率扩大2 149倍,证明该工程地质条件下3~#煤远程卸压4~#煤具有可行性.     

坚硬厚层顶板群结构破断的采场冲击效应

采用理论分析、物理相似模拟及现场实测相结合的方法,对坚硬厚层顶板群结构的破断冲击效应进行了分析.研究表明:多分层坚硬顶板群结构的破断冲击载荷在短时间内会产生较大的波动,工作面来压特征受多分层顶板垮断的联合作用;采场冲击来压强度主要与顶板赋存厚度及自身岩性特征有关,对于岩性相近的顶板岩层,厚度越大,对采场的矿压冲击影响也越剧烈,但厚层顶板垮断后的结构对其上覆顶板岩层的冲击载荷强度具有一定的缓冲.以大同矿区坚硬顶板群结构下的煤层开采为例,现场实测分析得到的工作面采场来压特征说明多分层顶板的垮断失稳有一定的随机性,但各分层顶板的单层垮断或多层同步垮断几率在整个煤层开采过程中基本保持不变.     

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.     

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.     

覆岩注浆减沉钻孔布置的试验研究

基于岩移关键层理论,通过试验与理论研究证明了采动覆岩离层主要出现在关键层下,并揭示了离层分布的动态规律．在此基础上论述了覆岩离层注浆减沉钻孔布置的原则,为注浆减沉钻孔设计提供了理论依据．     

Mechanisms of support failure and prevention measures under double-layer room mining gobs – A case study: Shigetai coal mine

In the practice of mining shallow buried ultra-close seams, support failure tends to occur during the process of longwall undermining beneath two layers of room mining goaf (TLRMG). In this paper, the factors causing support failure are summarized into geology and mining technology. Combining column lithology and composite beam theory, the key stratum of the rock strata is determined. A finite element numerical simulation is used to analyze the overlying load distribution rule of the main roof for different plane positions of the upper and lower room mining pillars. The tributary area theory (TAT) is adopted to analyze the vertical load distribution of each pillar, and dynamic models of coal pillar instability and main roof fracture are established. Through key block instability analysis, two critical moments are established, of which critical moment A has the greater dynamic load strength. Great economic losses and safety hazards are created by the dynamic load of the fracturing of the main roof. To reduce these negative effects, a method of pulling out supports is developed and two alternative measures for support failure prevention are proposed: reinforcing stope supports in conjunction with reducing mining height, or drilling ground holes to pre-split the main roof. Based on a comprehensive consideration of economic factors and the two categories of support failure causes, the method of reinforcing stope supports while reducing mining height was selected for use on the mining site.     

局部液化地层范围及埋深对隧道地震上浮的影响研究

杭州地铁4号线甬江路站-锦江站区间施工时需穿越大范围的可液化地层,为降低隧道在地震作用下上浮破坏的潜在风险,该区间选线时将隧道埋深进行了增大,从而使隧道部分处于非液化土层。为了研究在地震作用下盾构隧道局部液化地层范围以及隧道埋深对隧道上浮的影响,并对隧道调整后的抗震效果做出评价,采用有限差分软件FLAC^3D数值模拟与振动台试验相结合的方法,对处于不同液化土层分布范围、不同埋深的隧道地震上浮情况进行了数值分析及模型试验,研究结果表明：隧道液化地层范围越小,隧道上浮位移越小;当隧道埋深达14 m、隧道液化地层范围小于隧道范围一半时,隧道只发生轻微上浮;隧道设计时应尽量避免使隧道完全处于可液化地层中,可采取液化与非液化地层组合或增大埋深的方式,提高隧道结构的抗震安全性。     

F-structure model of overlying strata for dynamic disaster prevention in coal mine

The rupture and movement scope of overlying strata upon the longwall mining face increased sharply as the exploitation scale and degree growing recently, and the spatial structure formed by fractured strata became much more complex. The overlying strata above the working face and adjacent gobs would affect each other and move cooperatively because small pillar can hardly separate the connection of overlying strata between two workfaces, which leads to mining seismicity in the gob and induces rockburst disaster that named spatial structure instability rockburst in this paper. Based on the key stratum theory, the F-structure model was established to describe the overlying strata characteristic and rockburst mechanism of workface with one side of gob and the other side un-mined solid coal seam. The results show that F-structure in the gob will re-active and loss stability under the influence of neighboring mining, and fracture and shear slipping in the process of instability is the mechanism of the seismicity in the gob. The F-structure was divided into two categories that short-arm F and long-arm F structure based on the state of strata above the gob. We studied the underground pressure rules of different F-structure and instability mechanism, thus provide the guide for prevention and control of the F-structure spatial instability rockburst. The micro-seismic system is used for on-site monitoring and researching the distribution rules of seismic events, the results confirmed the existence and correct of F-spatial structure. At last specialized methods for prevention seismicity and rockburst induced by F-structure instability are proposed and applied in Huating Coal Mine.     

海孜煤矿顶板动力冲击水害的成因研究

离层水害是一种罕见而危害严重的灾害形式,本文通过水文地质分析、相似材料模拟、数值模拟和冲击水压试验证实发生在淮北海孜煤矿的顶板次生离层水害的成因。针对灾害原因,采取了采动疏干的防治水方法,取得了满意的效果,确保了类似条件工作面开采的安全。     

基于损伤力学的裂缝性储层流固耦合数值模拟

为了研究裂缝性储层裂缝的变形规律以及其对生产动态的影响,采用塑性损伤模型和双重孔隙介质模型相结合的流固耦合数值模拟方法,模拟了裂缝性储层注采过程中的裂缝和产量变化.采用迭代耦合方法模拟流体渗流与裂缝变形的耦合力学行为,并使用损伤变量从数学上表征储层裂缝的渗透率.分析了裂缝性储层开采时的损伤演化,获得了裂缝渗透率和地层压力的分布变化.结果表明,开采过程中地层裂缝逐渐闭合且渗透率降低,对产量造成不利影响.裂缝渗透率降低是导致地层产量下降的重要因素,裂缝性储层数值模拟时应考虑裂缝渗透率变化对生产带来的影响.