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.

Ground pressure and overlying strata structure for a repeated mining face of residual coal after room and pillar mining

To investigate the abnormal ground pressures and roof control problem in fully mechanized repeated mining of residual coal after room and pillar mining, the roof fracture structural model and mechanical model were developed using numerical simulation and theoretical analysis. The roof fracture characteristics of a repeated mining face were revealed and the ground pressure law and roof supporting condi- tions of the repeated mining face were obtained. The results indicate that when the repeated mining face passes the residual pillars, the sudden instability causes fracturing in the main roof above the old goal and forms an extra-large rock block above the mining face. A relatively stable ＂Voussoir beam＂ structure is formed after the advance fracturing of the main roof. When the repeated mining face passes the old goaf, as the large rock block revolves and touches gangue, the rock block will break secondarily under overburden rock loads. An example calculation was performed involving an integrated mine in Shanxi province, results showed that minimum working resistance values of support determined to be reason- able were respectively 11,412 kN and 10,743 kN when repeated mining face passed through residual pillar and goaf. On-site ground pressure monitoring results indicated that the mechanical model and support resistance calculation were reasonable.

山东省宁汶煤田鑫安煤矿3煤层开采水害隐患分析

为了查明鑫安煤矿开采3煤层的水害隐患类型,分析水害对矿井的潜在威胁和空间分布特征,采用现场质询、资料收集、井下踏勘的方法,逐一分析了煤矿大气降水及地表水、第四系砂砾层、新近系砂砾层、白垩系砂岩、3煤层顶底板砂岩、三灰、十下灰、奥灰、老空积水对3煤层开采的影响,排查分析出影响3煤层开采的水害隐患类型为3煤层顶底板砂岩、奥灰水和老空积水;采用“采后导水断裂带内含水层总厚度值”和“突水系数法”对开采3煤层的顶板砂岩充水危险性和底板奥灰突水危险性进行等级划分。研究分析出开采3煤层水害隐患的空间分布特征为3煤顶板水害主要影响矿井中部、老空水主要影响矿井浅部、奥灰水主要影响矿井东部。

Analysis of stability of coal pillars with multi-coal seam strip mining

Strip mining is one of the efficient measures to control surface subsidence and mining damage. However, the researches on the laws of the geological mining factors to upper and lower pillar's stability are still deficient in multi-coal seam strip mining at present. Based on the three dimension fast Lagrangian analysis of continua (short for FLAC3D) numerical simulation software, the laws of the stress increasing coefficient on the coal pillar and its stability were systematically studied for different depths, different mining widths, different interlayer spacings, different mining thicknesses, different properties of interstratified rock and the spacial relations of the upper and lower pillars in vertical alignment in multi-coal seam strip mining. The function relation between the stress increasing coefficient of upper and lower pillars with the mining depth, mining widths, interlayer spacing, mining thickness, property of interstratified rock and the spatial relationship were obtained.

A Data-Intensive FLAC^3D Computation Model:Application of Geospatial Big Data to Predict Mining Induced Subsidence

Although big data are widely used in various fields,its application is still rare in the study of mining subsidence prediction(MSP)caused by underground mining.Traditional research in MSP has the problem of oversimplifying geological mining conditions,ignoring the fluctuation of rock layers with space.In the context of geospatial big data,a data-intensive FLAC3D(Fast Lagrangian Analysis of a Continua in 3 Dimensions)model is proposed in this paper based on borehole logs.In the modeling process,we developed a method to handle geospatial big data and were able to make full use of borehole logs.The effectiveness of the proposed method was verified by comparing the results of the traditional method,proposed method,and field observation.The findings show that the proposed method has obvious advantages over the traditional prediction results.The relative error of the maximum surface subsidence predicted by the proposed method decreased by 93.7%and the standard deviation of the prediction results(which was 70 points)decreased by 39.4%,on average.The data-intensive modeling method is of great significance for improving the accuracy of mining subsidence predictions.

Roadway layout for recycling residual coal pillar in room-and-pillar mining of thick coal seam

In the context of a room-and-pillar mining gob in Shanxi province in China,this paper numerically investigates the stress distribution and deformation rules of roadway surrounding rocks at various locations of residual coal pillars in room-and-pillar mining gobs using software FLAC3 D.It is found that the concentrated stress beneath coal pillars distributes in a shape of ellipse.A reasonable roadway layout is then proposed.In this design,it is indicated that roadways should be designed to avoid the supporting zones of pillars with increasing compression and take into account the roof falling and crushing in the upper gob.According to the surrounding rock deformation characteristics and mining roadway locations as well as the supporting principles of timely support,rock reinforcing,piecewise management and suiting local conditions,a new asymmetric shield supporting plan is proposed.The field surveying results show that this supporting plan can effectively control the roadway rock deformation,thus guarantee the safe and smooth construction of roadways.

Additive manufacturing technology in mining engineering research

Nowadays,additive manufacturing,or 3D printing(3DP),though not a new technology in many industrial fields,is still relatively novel in mining engineering.This study explored the application of 3D metal printing,3D polylactic acid/acrylonitrile butadiene styrene printing,and 3D concrete printing in coal mining.Some examples of physical models established via 3DP technologies were studied in detail,namely,3DP bolts,3DP steel ladder beams,3DP face plates,and 3DP metal arches,which were installed in scaled 3DP concrete prototype models of coal mine excavation.Through the comprehensive laboratory loading tests,the models could simulate the damage scenario highly similar to the real failures.The results show that the 3D printed physical models greatly improved the accuracy and reliability of experiments.On this basis,the conceptual design of a 3DP machine for physical models was proposed,which had the potential of resembling the strata deformation/collapse in natural scenarios.Through assessing the applicability of the additive manufacturing technology in mining engineering,this study aimed to further explore its potential applicability in other engineering contexts such as slope controlling,large underground engineering,and underground space stability.

多煤层重复采动回采巷道失稳机理与控制技术

戊9-10-22290工作面为平煤六矿三水平二采区的孤岛工作面,风巷外段在采掘服务期间将会受到上覆戊8及下伏五矿己组回采影响,采掘时空关系异常复杂。目的为探讨多煤层重复采动回采巷道失稳机理与控制技术,方法基于采掘工作面应力时-空演化关系,提出平煤六矿戊9-10-22290工作面风巷外段全生命周期内的围岩控制方法,并进行现场工程应用。结果结果表明:上覆近距离煤层开采后,巷道顶板出现拉剪破坏;本煤层和下伏煤层回采过程中,巷道将逐段受到超前支承压力作用;根据巷道围岩所处的扰动时-空过程和高应力环境,提出“高预应力高强锚杆+锚索+深孔爆破卸压”的抗压-让压-卸压相结合的综合围岩控制技术。现场工业性试验表明,巷道服务期间两帮最大变形量为347 mm,顶板下沉和底板鼓起均在可控范围内,能够满足矿井安全生产需求,取得较好的技术和经济效益,结论研究结果可为类似条件下的回采巷道围岩控制提供参考。

厚煤层膏体分层充填开采地表移动变形规律研究

为探究厚煤层膏体分层充填开采地表移动变形规律,以古城煤矿1305工作面为研究对象,采用理论分析、参数计算及地表下沉预计等方法,基于等价采高理论建立了适用于膏体充填开采的等价采高模型,修正了非充分采动条件下的膏体充填开采预计参数,预计并揭示了厚煤层膏体分层充填开采后的地表移动参数变化规律。结果表明:膏体分层充填开采后地表最大下沉值270 mm,地表建筑物损坏等级在Ⅰ级允许变形以内,保证了地表建筑物的正常使用,为类似膏体充填后地表沉陷预测提供借鉴。

高强度重复开采覆岩与地表移动机理

为了给神东等大型煤炭生产基地生态修复和“三下”开采提供理论和技术支持,以实测方式为基础,深入研究了高强度重复开采地表移动特征和机理。分别对老采空区下开采、工作面隔离煤柱下开采、跨老采空区和隔离煤柱下开采这3种工况布设地表移动观测线,开展快速密集监测,采集了丰富的地表移动数据。结合井下推进过程,通过数据分析,获得了不同时期下沉和水平移动值,绘制了地表移动曲线时序图。研究表明:隔离煤柱对地表下沉的发展过程具有阻碍性、带动性和活化性等特征,水平移动方向对井下推进方向具有追随性等现象。据此建立了高强度重复采动条件下形成的块体岩层结构模型,分析了块状岩体在井下推进过程中平衡—旋转平移—再平衡的运动过程,揭示了地表移动实测曲线形态背后的岩层移动机理。研究成果可为该矿区或类似矿区开采沉陷预计模型建立和生态环境修复治理提供参考。

象山矿井主采3^#煤层涌水规律及充水因素分析

为查清矿井的涌水机理,为矿井防治水提供依据,依据大量生产资料,采用相关分析及理论分析相结合的方法,总结了象山矿井及主采3#煤层采面涌水规律,分析了充水因素,开展了煤层顶板含水层充水危险性预测。结果表明,矿井涌水量随着开采条件的变化总体呈现增高的变化趋势,采面涌水量具有背斜区低,向斜区高,回采期间具有先小后大,再由大变小的规律;充水通道主要为采动产生的顶板导水裂隙,充水水源主要来自煤层顶板山西组底部(K4)砂岩含水层与下石盒子组底部砂岩含水层水,涌水量大小与采面所在构造部位、顶板上覆含水层的岩性厚度及煤产量大小有关。在考虑采煤工艺和开采强度相同、同一采区构造类型相同、充水含水层富水性平面差异不够明显及大气降水及地表径流补给不变的情况下,依据顶板导水裂隙带范围内上覆砂岩含水层的岩性与厚度大小对3#煤层顶板含水层充水危险性进行了预测。为避免回采过程顶板突然涌水,应在顶板含水层充水危险性严重区采取事先疏放水措施。

基于ZY-3卫星数据的神东煤矿区土地退化人为影响因素调查与评价

基于ZY-3卫星数据,建立煤矿区土地退化人为影响专题因素遥感解译标志,对神东煤矿区土地退化人为影响因素开展遥感监测。运用层次分析法构建土地退化人为因素影响强度评价指标体系,采用综合评分法计算研究区土地退化人为因素影响强度指数。结果表明:土地压占破坏是造成神东煤矿区土地退化的首要人为影响因素,人类矿业活动对该区土地退化的影响程度已达"强烈"级别。为定量估算神东煤矿区矿业开发对土地资源的占用破坏数量并预测矿区土地退化发展趋势,提出1种煤矿区土地占用破坏率的计算方法。研究表明,ZY-3卫星数据完全满足井工开采煤矿区土地退化因素调查对高分辨率卫星数据的需求。今后需加强煤矿开发秩序的有效监管和矿山环境遥感动态监测,以防人为因素对土地退化的影响程度日益加深。

淮南矿业1/3焦煤资源禀赋特点分析探讨

介绍了淮南矿业1/3焦煤的煤质特点和炼焦特性,并将淮南矿业1/3焦煤与山东、黑龙江、内蒙古、河北、山西等地区的1/3焦煤进行了比较分析。结果表明,淮南矿业1/3焦煤具有低硫、黏结性强及结焦性好的特点,单独炼焦所得焦炭机械强度、反应性及反应后强度均优于1/3焦煤平均值;淮河一号镜质组平均最大反射率为0.932%,单独炼焦所得焦炭反应后强度高,兼具优良的结焦性和黏结性,属于变质程度较高的优质1/3焦煤;淮河二号低硫、黏结性强,可以作为1/3焦煤使用;淮河三号具有低灰、低硫的特点,可有效降低配合煤灰分、硫分。在优质焦煤、肥煤多为高硫煤的企业和地区,使用淮南矿业1/3焦煤可以提高煤源利用空间,改善配煤结构。

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。

布尔台矿井3^(-1)煤层冲刷带特征及预测

通过井下地质观测研究,对布尔台矿井3-1煤层冲刷带砂体的岩性、赋存特征和几何形态进行了描述,阐明了其识别特征。在对该矿井煤系沉积相分析的基础上,利用3-1煤层顶板砂岩等厚线图对冲刷带进行了预测,分析了矿井煤层冲刷带的总体分布规律。

特厚煤层重复采动作用下采空区自燃“三带”位移变化

为探究特厚煤层重复采动下采空区煤自燃“三带”的分布特征,基于束管监测系统,在铜川下石节煤矿222工作面进行现场实测,确定其自燃“三带”的分布规律。借助Fluent软件分别模拟重复采动及单一采动时采空区内氧气浓度的动态分布规律,发现重复采动采空区内实测结果与数值模拟结果基本一致。与单一采动模拟结果对比,重复采动导致采空区内部的散热带和氧化带出现缩短趋势;在进风侧散热带前移6.8%,氧化带前移7.0%;回风侧散热带前移14.3%,氧化带前移11.3%。研究成果能够为重复采动作用下采空区煤自燃危险区域防治提供依据。

新景矿3号煤层不同煤体结构煤孔裂隙的扫描电镜研究

采用扫描电镜对新景矿3号煤层不同煤体结构煤的微孔裂隙进行了观测和分析。结果表明,不同煤体结构煤中微孔裂隙发育特征不同,随着煤体结构破坏程度加剧,煤由脆性变形转化为韧性变形,煤中裂隙性质亦由剪性裂隙向张性裂隙发育过渡,煤中孔隙类型由原生孔和变质孔向外生孔发育过渡;煤中孔裂隙常见粒状、片状碎屑物质附着于表面和充填于煤孔裂隙中,裂隙的渗透性和孔隙的连通性均较差。

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。

鹤岗矿区1/3焦煤煤泥水絮凝沉降实验研究

为解决鹤岗矿区1/3焦煤煤泥水难沉降的问题,选取阴离子型、阳离子型及非离子型聚丙烯酰胺(PAM)为絮凝剂,对该矿1/3焦煤煤泥水进行絮凝沉降实验,研究搅拌时间、pH、絮凝剂种类和用量对煤泥水絮凝沉降效果的影响。结果表明:在搅拌强度100 r/min、搅拌时间45 s、pH为8、凝聚剂用量2 mL、非离子型PAM絮凝剂用量3 mL的条件下,该矿1/3焦煤煤泥水絮凝沉降效果最佳。该研究为鹤岗矿区1/3焦煤煤泥水处理提供了有益参考。

浅埋近距离煤层区段煤柱合理错距研究

神东煤田主要赋存浅埋近距离煤层,多数矿井上煤层都已开采结束,进入下煤层开采阶段。上下煤层区段煤柱的布置方式会直接影响覆岩与地表的下沉和裂隙的发育,使原本脆弱的生态环境进一步恶化。为确定合理的煤柱错距,以石圪台煤矿2-2煤和3-1煤开采为工程背景,结合物理和数值模拟开展研究。研究表明:当煤柱错距小于40 m时,上下区段煤柱裂隙场叠加发育,上煤层区段煤柱沉降;当煤柱错距等于40 m时,上下煤层区段煤柱裂隙场分离,上区段煤柱达到充分沉降;当煤柱错距大于40 m时,地表下沉与覆岩裂隙发育变化不大。故石圪台煤矿2-2煤和3-1煤的合理煤柱错距应大于40 m。