Underground pressure characteristics analysis in back-gully mining of shallow coal seam under a bedrock gully slope

我们在一个基岩溪谷斜坡下面在浅煤缝接在背溪谷采矿期间学习了地下的压力和它的机制，借助于物理模拟，数字建模并且地监视。结果证明地下的压力的紧张与它在 coalface 的相对位置有关。地下的压力是集中的，当 coalface 在溪谷的底部时，支持抵抗到达最大值，而地下的压力是中等的并且当 coalface 传递溪谷时，逐渐地减少。当斜坡在不稳定的、多边的块依赖了的采矿和形式组织的背溪谷期间在一个颠倒的方向旋转了到斜坡剧降时，这些变化的机制被分析，由于滑倒。当块破碎是小的时，多边的块的沉淀是可观的，导致在地下的压力的庞大的变化。随块身体的团的增加，块排水量将被减少与一起一增加在废矿由未破损的岩石和破岩石夹钳效果，导致地下的压力的减少。

Mechanism of Mining-induced Slope Movement for Gullies Overlaying Shallow Coal Seams

This paper provides an improved understanding of the movement mechanisms of both bed-rock gully and sandy soil gully when underground mining occurs underneath,followed by systematic analysis of the contributing factors such as mining advance direction,gully slope angle,gully erosion coefficient and mining height.This paper presents the results from monitoring,theoretical analyses and up to date modeling based on the geological features in the gully affected area,and the implications of these results to the success of roof support trial.It was observed that when mining occurred towards the gully,sliding of slope block along the fracture surface occurred,which resulted in unstable roof condition;when mining progressed away from the gully,polygon blocks developed in the gully slope and rotated in reversed direction forming hinged structure;within the bed-rock slope,the hinged structure was unstable due to shear failure of the polygon block;however,within the sandy soil slope,the structure was relatively stable due to the gradual rotating and subsiding of the polygon block.The increase of the value of slope angle and mining height lead to a faster and more intensive fracture development within the gully slope,which had a pronounced effect on gully slope stability and underground pressure.Various remediation approaches are hence proposed in this paper including introducing more powerful support and reasonable mining height,setting up working face along or away from gullies,using room and pillar,strip mining and backfill instead of longwall mining.

Simulation research on the influence of eroded primary key strata on dynamic strata pressure of shallow coal seams in gully terrain

In Huojitu Coal Mine of Shendong mining area, the dynamic strata pressure (DSP) accidents occurred when the working faces passed the gully terrain. Focusing on this problem, we used physical simulation experimental method to thoroughly study the influence of eroded overlying primary key strata (PKS) in the gully terrain on DSP of shallow coal seams in this paper. The result show that when mining activities took place in the uphill section of shallow coal seams in gully terrain and the PKS were eroded, the blocks could not form stable bond-beam structures since the horizontal force of PKS blocks in adjacent sloping surfaces were relatively small. The sliding instability of blocks caused rapid increase of the load on the sub-key strata (SKS) blocks, which resulted into coal slide and roof fall as well as sharp drop of active columns. This led to DSP phenomenon. When the PKS blocks were intact, there was no DSP phenomenon to enable blocks provide certain horizontal force to maintain stable bond-beam structure. The simulation results were verified by the mining practices of working face 21306 crossing the gully terrain in the Huojitu Coal Mine.

Fracture mechanics model of fully mechanized top coal caving of shallow coal seams and its application

Based on break characteristics of roofs in fully mechanized top-coal mining of thick shallow coal seams, a fracture mechanics model was built, and the criterion of crack propagation in the main roof was derived using the fracture mechanics theory. The relationships between the fracture length of the roof and the working resistance of the supports were discovered, and the correlations between the load on the overlying strata and the ratio of the crack's length to the thickness of the roof were obtained. Using a working face of Jindi Coal Mine, Xing county Shanxi province as an example, the relationships between the fracture length of the roof and the working resistance of the supports were analysed in detail. The results give a design basis in hydraulic top coal caving supports, which could provide useful references in the practical application. On-site experiment proves that the periodic weighting step interval of the caving face is 15–16 m, which is basically consistent with the theoretical analysis results, and indicates that the mechanized caving hydraulic support is capable of meeting the support requirements in the mining of a super-thick but shallowly buried coal seam.

Characteristics and stability of slope movement response to underground mining of shallow coal seams away from gullies

Underground pressure is abnormal during mining of shallow coal seams under gullies. We studied gully slope movements, subject to underground mining, with physical simulation and theoretical analysis. The rules disclose that the slope rock slides horizontally in response to mining in the direction of gullies and rotates reversely with the appearance of a polygon block in mining away from gullies. We focused our attention on the case of mining away from a gully. We built a mechanical model in terms of a polygon block hinged structure and investigated the variation of horizontal thrust and shear force at the hinged point in relation to the rotation angle under different fragmentations. The Sliding-Rotation instability conditions of the polygon block hinged structure are presented based on the analyses of sliding instability and rotation instability. These results can serve as a theoretical guide for roof control during mining away from gullies in a coalfield defined by gullies.

Ground fissure development regularity and formation mechanism of shallow buried coal seam mining with Karst landform in Jiaozi coal mine: a case study

A comprehensive study was undertaken at Jiaozi coal mine to investigate the development regularity of ground fissures in shallow buried coal seam mining with Karst landform,shedding light on the development type,geographical distribution,dynamic development process,and failure mechanism of these ground fissures by employing field monitoring,numerical simulation,and theoretical analysis.The findings demonstrate that ground fissure development has an obvious feature of subregion,and its geographical distribution is significantly affected by topography.Tensile type,open type,and stepped type are three different categories of ground fissure.Ground fissures emerge dynamically as the panel advances,and they typically develop with a distance of less than periodic weighting step distance in advance of panel advancing position.Ground fissures present the dynamic development feature,temporary fissure has the ability of self-healing.The dynamic development process of ground fissure with closed-distance coal seam repeated mining is expounded,and the development scale is a dynamic development stage of“closure→expansion→stabilized”on the basis of the original development scale.From the perspective of topsoil deformation,the computation model considering two points movement vectors towards two directions of the gob and the ground surface is established,the development criterion considering the critical deformation value of topsoil is obtained.The mechanical model of hinged structure of inclined body is proposed to clarify the ground fissure development,and the interaction between slope activity and ground fissure development is expounded.These research results fulfill the gap of ground fissures about development regularity and formation mechanism,and can contribute to ground fissure prevention and treatment with Karst landform.

富水沟谷区浅埋煤层导水裂隙演化特征

富水沟谷区域下浅埋煤层赋存条件特殊,采场上覆岩层导水裂隙发育演化特征复杂。为了揭示沟谷区浅埋煤层在回采扰动作用下覆岩裂隙演化规律,以朱家峁煤矿1305-2工作面过沟谷区回采阶段为工程背景,采用理论分析、物理相似模拟、数值模拟与现场效果验证的方法,建立了覆岩裂隙−渗流场概念模型,开展了覆岩结构发育与微震能量演化研究,分析了覆岩变形与塑性破坏分布特征,提出了针对沟谷区下浅埋煤层导水裂隙防治措施,并应用于现场工程实践。结果表明:开采扰动下裂隙−渗流场模型呈“梯台”结构,并依次划分为初渗区域、稳渗区域、紊渗区域3个区域;将所研究矿井的工况数据代入模型结构,计算出各个渗透区域范围,并根据计算结果对矿井的稳渗区域采取注浆措施。工作面回采至沟谷区段,覆岩裂隙域形态呈现“拱形-梯形-复合梯形”的扩展演化特征,裂隙纵向发育高度达到163 m,并与沟谷区地表贯通。随工作面推进,地表裂隙依次经历“滑移-挤压-撕裂”过程;沟谷区域位移云图呈现出滞后开采“高位梯形”破断形态,在沟底处下沉位移最大,达3.47 m。针对开采导致的裂隙大范围扩展贯通,提出在地面进行采动裂缝注浆处理,在工作面上覆岩层进行注浆封堵,实现过沟谷区开采“井上−井下”联合防治,保证安全开采。该研究结果可为浅埋煤层的过沟谷区开采、采动裂隙防治及富水区“保水采煤”提供新的科学依据。

浅埋煤层开采覆岩“梯形”破断参数与裂隙演化分析

目的为了探究浅埋煤层开采覆岩“梯形”破断参数与裂隙演化规律间的关联机制,并量化表征覆岩垮落、裂隙分布特征,方法以崖窑峁煤矿为研究对象,采用理论分析、物理相似模拟、数值模拟、现场实测相结合的方法,分析覆岩垮落空间分布形态,并量化表征上覆岩层垮落“梯形”的分布参数。结果结果表明:上覆岩层受煤层开采扰动影响,沿两侧破断线整体呈“梯形”形态,由于破断角φ,γ不同,故覆岩采动裂隙在空间上呈非对称“斜四边形”裂隙发育体的展布形态,结论基于理论计算得出崖窑峁矿业30204工作面覆岩垮落分布形态,覆岩垮落两侧破断角开切巷处破断角φ∈[58.7°,68.7°],采煤机机头处破断角γ∈[60.8°,67.8°],并根据破断角公式进一步计算,得出开切巷处覆岩垮落长度Lφj=11.5 m;采煤机机头处覆岩垮落长度Lγj=10.4 m。依据现场30204工作面3-1煤层顶板垮落实际监测数据,得出上覆岩层垮落的最佳高度为11~30 m,裂隙发育最佳宽度在距离工作面开切巷5 m和采煤机机头5 m范围内。

神东矿区浅埋煤层开采地表裂隙分布及动态演化特征研究

神东矿区浅埋煤层群开采导致地表裂隙发育良好,立体漏风复杂。为研究神东矿区地表裂隙分布特征及动态演化规律,以大柳塔煤矿活鸡兔井和补连塔煤矿浅埋藏开采为工程背景,采用现场无人机定点观测、红外、地质雷达等技术相结合的方法,研究地表宏观裂隙、隐蔽裂隙分布特征,并对裂隙动态演化规律进行分析。结果表明:神东矿区浅埋煤层开采工作面采空区对地表走向裂隙的影响相比于倾向裂隙较大,其中活鸡兔井12下206工作面101条裂隙有效影响范围35 m,补连塔煤矿22310工作面122条裂隙为62 m,走向裂隙最大裂隙宽度达到80 cm,倾向裂隙普遍在10 cm以下;随工作面的推进,裂隙宽度逐渐变大,直至发育完全,裂缝位置不连续断面间距变大,落差增大;宽度较大的裂隙(裂隙宽度大于10 cm),如果距离工作面较近,随着工作面的推进,裂隙宽度会逐渐缩小,甚至可能闭合。

近浅埋多层厚硬顶板大采高综放工作面矿压显现规律研究

针对榆神矿区近浅埋多层厚硬顶板条件下,“大周期”来压支架立柱下缩量大、煤柱应力集中系数高、稳定性差等强矿压问题,采用了数值计算、微震和煤体应力监测等技术手段,对覆岩破断运动及工作面来压规律进行了分析研究,结果表明:覆岩破断运动上,多层厚硬顶板较大的“垂向离层空间”和“自下而上”的顺次交替垮落孕育了顶板“高+低层位组合破断”的时空基础;“高低层位顶板组合破断”是“大周期”来压增强的关键诱因;同时,煤柱应力的时空演化受控于多层厚硬顶板的破断垮落。矿压显现上,工作面“大周期”立柱下缩量平均可达945 mm,持续距离12.10 m,并可由2~5次连续强来压组成;巷道煤柱应力集中系数达到1.80~2.30,影响范围为工作面前方126 m至后方471.3 m,具有明显的“高强度、大范围、长上升期”特点。针对该条件下的强矿压防治,分别提出了“弱化低位顶板、优化破断结构”和“弱化高位顶板、改变破断次序”的技术思路,并取得的了较好的应用效果。

浅埋煤层房采破坏区充填复采技术研究与应用

针对浅埋煤层前期开采遗留的大量房采破坏区严重影响现阶段工作面正常开采的问题,以五家沟煤矿5-1号煤层15301工作面的赋存情况和开采条件为研究背景,采用煤矿探巷机器人和机载三维激光扫描系统,探查出靠近15301辅运巷道三个房采区的情况,对房采破坏区失稳机理进行研究,确定了破坏区支护强度,通过对充填材料不同配比实验,同时结合填充效果的探查结果,提出了安全快速通过充填区技术。研究与实践表明:当破坏区支护强度P_(k)≥2.1 MPa时,可避免房采破坏区失稳;确定了满足五家沟煤矿充填的主体材料为充填料Ⅰ,其中,水泥、粉煤灰掺入比例为3∶7,水灰比为1∶(0.8~1.2);对房采区进行充填后,利用安全快速通过充填区技术,顺利完成了15301工作面房采破坏区充填复采,取得了良好的技术与经济效益,为类似条件下的浅埋煤层开采提供技术借鉴。

浅埋近距离煤层过斜交区段煤柱开采矿压规律研究

为了探究浅埋近距离煤层工作面开采过不同斜交角度煤柱的矿压规律,保障工作面安全高效回采,采用现场实测和数值模拟相结合的方法,分析了11°、30°、45°、60°和75°斜交角度的采动应力演化特征,揭示了工作面过不同斜交角度煤柱的应力变化规律。结果表明:根据过11°斜交煤柱矿压规律实测,工作面来压位置随煤壁与斜交煤柱叠加区而移动,在工作面中部压力最大,机尾次之,机头最小;工作面机尾过煤柱时应力集中最明显;中部过斜交煤柱时,随着斜交角的增大,超前煤壁峰值应力自30°以内为中部宽缓单峰,45°~75°为中部斜交区和机尾双峰,且机尾峰值较大;机尾最大超前应力峰值随斜交角的减小而增大,峰值越靠近机尾;斜交角超过45°时工作面中部出现应力峰值,表现为双峰,该研究可为类似工作面过斜交煤柱开采提供借鉴意义。

浅埋煤层采动诱发覆岩应力响应及地裂缝动态发育特征

为探究浅埋煤层综放采动诱发覆岩应力响应及地裂缝动态发育特征,利用UDEC软件对甘肃环县甜水堡矿区采煤过程中地裂缝的发育情况、应力变化情况进行数值模拟。研究表明:随着工作面的不断推进,地裂缝由下而上发育并且越发密集,采空区范围大到一定程度时,中部岩层被压实,临时性裂缝呈自闭合特征,永久性裂隙存在于采空区两侧。上覆岩层的下沉位移区域随工作面推进距离增大而增大,呈现出采空区两侧下降距离最少,越靠近采空区中部对称轴中心下降距离越深的趋势。采空区上覆岩层应力变化依次为应力集中、损伤变形、断裂坍塌到应力释放的过程。

浅埋近煤层群采动“三区”漏风裂隙场时空演化规律数值模拟

浅埋近煤层群采动下,地面采空区工作面“三区”之间易形成连通的漏气通道引发工作面低氧和采空区煤自燃,如何厘清采动效应下浅埋煤层群“三区”漏气通道的时空分布演化规律是有效防控煤自燃和低氧的关键。以陕煤柠条塔煤矿S1232工作面为研究背景,采用理论与数值模拟相结合的方法,研究了单一煤层、复合煤层重复开采下覆岩破坏特征,分析了煤层间距与采厚对裂隙二次发育的影响规律。结果表明:浅埋近煤层群开采下上覆岩层裂隙仅存在垮落带与裂缝带,主关键层破断后裂缝带快速发育至地表,关键层周期破断控制地表裂隙周期生成与下沉;上煤层裂隙密度发育由原始阶段先后经历快速增长、稳定和二次增长3个阶段;随采厚增大,各区间裂隙密度增大,大裂隙发育更充分,裂隙宽度整体增大;随煤层间距增大,小于0.2 m的裂隙宽度随采厚增大,且增加的速度逐渐加快,大于0.2 m的裂隙宽度随采厚增大,但增加速度逐渐变缓;采厚相同时,裂隙宽度大于0.2 m的裂隙密度随着煤层间距的增大逐渐减小。

浅埋近距离煤层工作面过平行煤柱开采强矿压显现规律

浅埋近距离煤层工作面过平行煤柱开采容易发生强矿压压架事故,严重影响工作面安全高效开采。以榆家梁煤矿43207工作面和石圪台煤矿2^(-2上)102及2^(-2上)103工作面为背景,采用理论分析、物理模拟和现场实测相结合的方法,根据间隔岩层厚度和煤柱应力传递影响角,提出了过煤柱阶段划分判据,重点分析了不同间采比G、水力压裂程度条件下,过平行煤柱不同阶段的矿压显现特征。结果表明:由于上覆遗留煤柱及倒梯形覆岩结构的作用,导致煤柱影响阶段来压时支架平均载荷最大,进煤柱阶段次之,出煤柱阶段最小,强矿压位置主要集中在出煤柱影响阶段范围;间采比越小,工作面过煤柱采动期间来压时支架平均载荷越大,间采比G=5.5较G=10在进煤柱阶段、煤柱影响阶段和出煤柱阶段分别增大14.6%、14.2%和23.5%,动载效应越明显;间采比对周期来压步距影响不大,总体上煤柱影响阶段的周期来压步距是进出煤柱阶段的1.6~2倍,周期来压步距越大造成顶板悬伸长度增大,导致工作面来压时支架载荷明显。根据过煤柱阶段不同水力压裂范围的矿压规律分析,压裂后的支架平均载荷较未压裂减小11.2%~15%,来压步距减小7.8%~20.3%,水力压裂效果较明显,可有效地降低工作面过煤柱采动的强矿压风险,为类似开采条件的强矿压控制提供借鉴意义。

浅埋煤层留小煤柱沿空掘巷技术研究与应用

在凤红煤业151302工作面采用沿空掘巷工艺技术,通过理论计算并结合数值模拟,综合分析确定了小煤柱的合理尺寸为5.0 m,同时优化了小煤柱巷道支护参数方案。工程应用结果表明:采用留小煤柱沿空掘巷技术,锚杆索受力远低于破断载荷;巷道顶板下沉位移在200 mm之内,回采帮内位移位小于200 mm,煤柱帮内位移在150 mm之内,巷道围岩和小煤柱皆处于稳定结构状况,整体围岩控制效果良好。

基于三维曲面积分的矿压实测数据分析模型及应用

针对影响综采面正常推进的异常矿压显现进行预测与防控是减少工作面顶板事故隐患的有效措施,合理有效的矿压实测数据分析方法是关键技术之一。基于三维曲面积分理论,引入Kriging插值算法,提出一种“寻找大显现、关注异常点”的矿压数据分析模型。以顶板压力与底板比压组建三维曲顶柱体,以液压支架与累计进尺组建二维坐标面,从而建立基于三维曲面积分的矿压实测数据分析模型,并以压力曲面向割平面投影算法实现对矿压实测数据的解析与预测分析。开展神东矿区补连塔煤矿12514工作面的矿压监测数据分析,获得了矿压显现明显区域、矿压三维曲面投影模型以及实时矿压云图,提取显著来压区域8次,指向62号支架~98号支架区域6次,其中,显著来压区域持续平均距离11.9m,表明基于三维曲面积分分析模型可选取顶板运动比较剧烈的区域,相对于传统统计分析方法具有更强的针对性,验证了所提出分析模型的合理可靠性。

浅埋深厚硬基岩综放工作面覆岩运移破坏规律研究

为揭示浅埋厚煤层综放工作面顶板来压及覆岩运移特征,在五家沟矿15304工作面辅运巷内施工钻孔,现场重探顶板岩层分布及关键层位置,并对来压期间的顶板不同层位的裂隙发育特征及破断位置进行监测,分析工作面支架工作阻力分布规律。结果表明:顶板关键层控制工作面覆岩运移及工作面矿压显现,关键层破断引起覆岩剧烈运动及采场剧烈来压,采空区覆岩垮落以规则的弧线状向上发育,其中由顶板中间底部向上部、两端逐渐递减,覆岩破坏形态易形成“马鞍形”。由于亚关键层厚度及强度较大,导致15304工作面推进90 m时亚关键层才发生破断引起初次来压,周期来压过程中导水裂隙带逐步向上发育到主关键层附近,厚硬关键层阻断了顶板裂隙继续向上发育。该工作面初次来压步距90 m,周期来压来压步距22 m;覆岩垮落带最大发育高度为44 m左右,导水裂缝带最大发育高度为58 m。

安山煤矿浅埋煤层覆岩导水裂隙带发育高度实测研究

为了研究庙哈孤矿区浅埋煤层开采导水覆岩裂隙带发育规律,以安山煤矿133103工作面为研究背景,采用理论分析与现场实测相结合的手段对3-1煤层开采后覆岩裂隙发育规律进行研究。结果表明,133103工作面垮落带高度10.69~15.88 m,垮采比为4.86~5.73,导水裂隙带发育范围52.33~62.52 m,裂采比为23.8~28.4。研究成果为庙哈孤矿区类似条件下工作面开采顶板水灾害防治提供参考。