Coal and rock fissure evolution and distribution characteristics of multi-seam mining

Henan Pingdingshan No.10 mine is prone to both coal and gas outbursts.The E_(9-10)coal seam is the main coal-producing seam but has poor quality ventilation,thus making it relatively difficult for gas extraction.The F_(15)coal seam,at its lower section,is not prone to coal and gas outbursts.The average seam separation distance of 150 m is greater than the upper limit for underside protective seam mining.Based on borehole imaging technology for field exploration of coal and rock fracture characteristics and discrete element numerical simulation,we have studied the evolution laws and distribution characteristics of the coal and rock fissure field between these two coal seams.By analysis of the influential effect of group F coal mining on the E_(9-10)coal seam,we have shown that a number of small fissures also develop in the area some 150 m above the overlying strata.The width and number of the fissures also increase with the extent of mining activity.Most of the fissures develop at a low angle or even parallel to the strata.The results show that the mining of the F_(15)coal seam has the effect of improving the permeability of the E_(9-10)coal seam.

Coupling control on pillar stress concentration and surface cracks in shallow multi-seam mining

In order to ensure safe mining and reduce surface damage in shallow multi-seam mining,the failure characteristics of interburden strata with different coal pillars offset distances between pillars in the upper and lower seams,the distribution characteristics of stress concentration in coal pillars,and the development characteristics of stratum cracks and subsidence were investigated by physical and UDEC2D simulation.Meanwhile,the effect of different coal pillar offset distances on stress concentration of coal pillar and development of stratum cracks were studied.Based on those results,a formula for safe mining and reducing surface damage was established,which provided a theoretical basis for safe and environmentally friendly mining in shallow multi-seam.According to the results,the optimal coal pillar offset distance(the side to side horizontal distance of the upper and lower coal pillars)between the upper and lower coal seams was developed to reduce the stress concentration of coal pillars and surface damage.The results of this study have been applied in Ningtiaota coal mine and have achieved good results in safe and environmentally friendly mining.

Geomechanics of subsidence above single and multi-seam coal mining

Accurate prediction of surface subsidence due to the extraction of underground coal seams is a significant challenge in geotechnical engineering. This task is further compounded by the growing trend for coal to be extracted from seams either above or below previously extracted coal seams, a practice known as multiseam mining. In order to accurately predict the subsidence above single and multi-seam longwall panels using numerical methods, constitutive laws need to appropriately represent the mechanical behaviour of coal measure strata. The choice of the most appropriate model is not always straightforward. This paper compares predictions of surface subsidence obtained using the finite element method, considering a range of well-known constitutive models. The results show that more sophisticated and numerically taxing constitutive laws do not necessarily lead to more accurate predictions of subsidence when compared to field measurements. The advantages and limitations of using each particular constitutive law are discussed. A comparison of the numerical predictions and field measurements of surface subsidence is also provided.

Lateral Stress Concentration in Localized Interlayer Rock Stratum and the Impact on Deep Multi-Seam Coal Mining

To explore the impact of lateral stress concentration in interlayer rock stratum on the exploitation of protected coal seam, a field experiment was carried out in a multi-seam mining structure. Lateral stress redistribution and interlayer rock failure behavior were surveyed. Then an assistant numerical investigation was implemented to evolve the effect of liberated seam mining and its influence on stress reconstruction in surrounding rock mass. The cause of lateral stress concentration and its impact were discussed finally. Key findings turn out that a certain lateral stress increases in interlayer rock stratum and concentrates on its lower region. Lateral stress concentration and interlayer rock failure are interactional. The former is an inducing factor of the latter;the latter promotes the increase of concentration degree. Extent of lateral stress concentration increases to the maximum as seam distance is about 50 m. But the efficacy of liberated seam mining decreases as the seam spacing gets larger. Protected seam mining is then classified based upon the impact of lateral stress concentration, which helps to prevent the rock burst hazard and then to achieve a reliable mining in deep mines.

Interlayer interference mechanism of multi-seam drainage in a CBM well:An example from Zhucang syncline

Based on the characteristics of the strong volatility of physical property in vertical direction, high gas content, high resource abundance and large exploitation potentiality of coal reservoir in Bide-Santang basin of Zhina coal field, we study the generation mechanism of interlayer interference, propagation rules of reservoir pressure drop and influencing factors of gas productivity in CBM multi-seam drainage in the paper. On the basis of the actual production data of X-2 well of Zhucang syncline in Bide-Santang basin,by simulating the gas production process of a CBM well under the condition of multiple seam with COMET3 numerical simulation software, we analyze the influencing factors of gas productivity during the process of multi-seam drainage, and illuminate the interlayer interference mechanism of multiseam drainage. The results show that permeability, reservoir pressure gradient, critical desorption pressure and fluid supply capacity of stratum have great influence on gas productivity of multi-seam drainage while coal thickness has little influence on it. Permeability, reservoir pressure gradient and fluid supply capacity of stratum affect the propagation velocity of reservoir pressure drop and thereby affect the final gas productivity. Moreover, the influence of critical desorption pressure on gas productivity of multiseam drainage is reflected in the gas breakthrough time and effective desorption area.

Model test of the overburden deformation and failure law in close distance multi-seam mining

Based on characteristic of the associated mining of multi-coal seam and the engineering geological characteristics of overburden,the mining impact pattern of multi- seam mining and the dynamic fracture mechanism of overburden were characterized by applying the engineering geological mechanical model test.The related strata movement parameters and influence area of multi-seam mining were obtained,the strike boundary angle is 61°,the full extraction coefficient is 0.93,the greatest subsidence angle is 81°,the horizontal movement factor is 0.38,the deviation of inflection point/mining deep is 0.11. The development height of caving zone and water flowing fractured zone of multi-seam mining were calculated,is 32 m and 81.5 m separatly.The assess of influence degree of coal layer safety mining is that,there exists the possibility of water and sand inflow when mining,some messures for mine water prevention and control should be used,and the mining thickness should be local strictly limit.

De-stressed mining of multi-seams:Surrounding rock control during the mining of a roadway in the overlying protected seam

在 overlying 的包围岩石控制保护的煤缝接是为缝接得多的煤的强调 de 的采矿的一个挑战性的话题。车道控制上的当前的研究调查结果在有变化厚度的一个复杂粗糙的房顶的一个物理模型的设计被使用。模型被用来学习动态压力引起的车道不稳定性和倒塌。结果证明当房顶的厚度超过固定深度时，车道安全是最少的，房顶为倒塌有最大的可能性。数字模拟也被执行在内在的保护的缝接采矿期间在车道挖掘前后学习压力再分配。车道排水量和骨折的进化由支持方法影响了很好被学习了。为采矿的一系列支持原则和技术影响了车道在 Huainan 矿在成功的实际申请的示范以后被建议了。这些原则和技术具有到在中国的深煤采矿支持的扩大价值。

河流下多煤层开采安全性及保护技术

我国新疆地区干旱缺水,艾维尔沟河作为新疆一条具有重要地理特征和环境影响的河流,其对于流经区域的经济、生态都具有重要意义,因此在艾维尔沟河下进行煤炭开采时,既要保证矿井安全也要保证河流的正常使用。采用理论分析、数值模拟等方法对河流下多煤层开采安全性及河流保护技术进行研究,通过理论计算得到多煤层开采条件下,覆岩导水裂隙带发育高度(11401工作面为41.9 m、1502工作面为110 m、11401工作面为113.8 m)并绘制剖面示意图;同时,采用数值模拟方法对覆岩导水裂缝发育形态及高度进行确定,最终基于导水裂隙带高度(117.8 m)与最小煤层埋藏深度(191.5 m)的相互关系,确定河流下开采是安全的可行的。在保证河流下煤层安全开采的前提下,通过分析离层注浆原理,并结合采动影响特征参数及工程现场,提出了以离层注浆为主,河道防渗及优化开采设计为辅的多手段对采动影响范围内地表特定目标的精准保护技术。根据实际采矿地质条件,采用概率积分法计算试采工作面开采前后河道位置处地表移动变形,计算结果显示:采用离层注浆精准保护技术后,河道的最大水平变形值(2 mm/m)未超出允许坝体的极限变形值(2.5 mm/m),所以采用离层注浆精准保护技术可以实现,井下安全开采的同时,保证河道的正常使用。通过对河流下多煤层开采的安全性及保护技术的分析研究,为矿山绿色开采提供参考和借鉴。

近距离多煤层下行重复采动覆岩变形与裂隙演化特征研究

随着地壳浅部易采煤炭资源的逐渐枯竭,复杂地质条件下的多煤层开采将成为新常态。由于多煤层开采对上覆岩体造成极大的重复扰动,导致覆岩的垮落、移动与裂隙演化规律相较于单一煤层开采更加复杂。为了研究多煤层下行重复采动条件下覆岩变形与裂隙演化特征,本文以陕北神府矿区张家峁煤矿4^(-2)煤层、4^(-3)煤层、4^(-4)煤层、5^(-2)煤层开采为研究对象,进行了几何相似比1∶100的相似模型试验和UDEC数值模拟研究。张家峁煤矿四层煤层下行重复采动物理相似模拟和数值模拟分析结果表明,周期来压步距随下行开采呈逐渐减小的规律,冒落带高度与煤层厚度正相关,4^(-2)煤层开采后导水裂隙带贯穿至地表,4^(-3)煤层、4^(-4)煤层、5^(-2)煤层开采结束后,导水裂隙带均贯穿层间覆岩。顶板围岩在反复拉伸、挤压作用下,破碎程度逐渐增大,且多为未闭合裂隙。研究结果可以为多煤层开采条件下的顶板管理和开采设计提供理论层面的参考和指导。

无人机影像拼接多分辨率自适应无缝融合方法

本文针对无人机影像拼接中存在的几何错位和拼接缝问题,提出了一种联合应用最佳拼接缝算法和图像融合的方法,对影像几何错位和拼接缝区域进行修复和无缝融合。首先利用图切割算法搜索帧间拼接最小差异线,修复帧间几何错位;然后基于差异线建立条带融合兴趣区,且融合兴趣区范围大小随帧间色调曝光差异大小自适应变化;最后引入融合兴趣区掩膜改进拉普拉斯多分辨率图像融合算法,对帧间色调曝光差异进行平滑处理,实现无人机影像拼接的无缝融合。试验结果表明,相较于传统拉普拉斯融合算法,本文影像融合成果互信息平均提升了12.79%,峰值信噪比平均提升了21.48%,取得了自然无缝的目视效果,具有一定应用价值。

西湖凹陷K气田地震储层预测中去除煤层影响技术及其应用

煤层引起的强反射对地震信号有极强的干涉作用。东海陆架盆地西湖凹陷K气田煤层发育,且具有“横向上连续性差、分布零散,纵向上期次多、厚度薄”的特点。研究发现,煤层的存在会导致该区砂体预测存在无中生有、地震反射结构被屏蔽等问题,严重制约了地震储层预测的精度,因此,应用地球物理半定量解释定位煤层、地震高幅滤波过滤煤层、多子波分解重构置换煤层等方法,在尽量多保留有效地震反射信息的基础上去除K气田煤层强反射对地震信号的影响。消除煤层强反射后的地震数据与储层相关性更高,提升了储层预测精度和可靠性。

多层叠置含煤系统煤层瓦斯赋存规律及影响因素分析

基于煤层瓦斯地质理论,通过大量的煤田勘探采样数据分析,研究总结陈家沟煤矿瓦斯赋存规律及其影响因素。矿区煤层瓦斯赋存主要受地质、构造、煤岩特征、顶底板岩性、埋藏深度等的影响。陈家沟煤矿属高瓦斯矿井,瓦斯分带以CH4带为主;瓦斯含量随着煤层的埋藏深度增加而有增大趋势,埋深达到700 m左右时,瓦斯含量达到最高;区内可分为三个独立含气系统,分别为C1~C12、C14~C26、C31~C69含气系统。经过研究分析,今后在矿井开发中应考虑相应合层排采独立开发。

基于多重约束的铁路隧道净空检测研究

为解决铁路隧道洞内无法准确获取扫描仪定位参数和高精度三维点云数据成果难题,基于激光扫描仪、惯性测量单元、里程计等传感器,提出多源数据融合处理算法,获得三维点云相对数据成果;利用隧道自身的环缝、螺栓孔洞结构形状特征,生成点云灰度及深度影像,实现管片环缝提取,结合环片固定宽度完成里程校准;根据误差传播规律引入靶标控制点联合解算,修正定位定姿误差和坐标转换,获取工程坐标系统下的三维点云数据;基于最小二乘二维ICP匹配算法进行点云模板匹配,提取轨道中心线。经实验测试,对里程及靶标控制等多重约束后,获得的三维绝对点云平均误差为3.2 cm;提取隧道断面,输入隧道设计断面线并等分处理,与轨道基准坐标系进行匹配,逐点计算断面激光点到设计轮廓线的垂直距离,完成了隧道净空检测。实验数据分析表明,基于惯性测量单元/里程计组合导航误差纠正模型,在里程及靶标控制等多重约束后,能够获得高精度的铁路隧道三维点云数据成果,实现铁路隧道的净空检测。

分段多簇密切割压裂技术在淮南矿区煤层气抽采中的应用

针对淮南矿区碎软低渗煤层瓦斯抽采技术难题,以13-1煤层为例,在分析煤层及其顶底板概况的基础上,采用煤层顶板分段压裂水平井技术,充分利用水平井水平段,单段分3簇射孔,簇间距25 m,实现分段多簇密切割体积压裂改造。微地震监测结果表明,单段裂缝长度102.5~211.4 m,缝高17.3~27 m,裂缝主体向下延伸,实现了井筒与煤层的沟通。排水采气效果表明,最高产气量1519 m^(3)/d,取得了良好的产气效果。研究成果为淮南矿区煤层气地面预抽和瓦斯区域治理提供了工程借鉴。

告成煤矿极软煤层钻孔煤水分离技术研究及应用

为防治松软低透气性煤层瓦斯灾害,采用水力冲孔、割缝等卸煤增透措施在瓦斯抽采中愈加普遍,带来钻孔煤水分离难题。针对告成煤矿极软煤层煤泥不易沉降、煤水分离效率低的问题,开展了煤泥粒径分布特征分析和穿层钻孔煤水分离方法应用考察。结果发现,松软煤层在高压水力作用下极易形成微细煤泥,煤粒分布符合Rosin-Rammler函数,特征粒径尺寸为0.84 mm,细微煤泥粒径分布较为均匀;煤袋围堰沉淀、振动筛式分离机、板框式压滤机等单级分离方法在应用中存在效率低、劳动强度大、计量不精准等问题。基于试验结果,提出并应用了穿层钻孔煤水多级分离工艺方法,利用不锈钢焊接式条缝筛网进行初级过滤分离,布置巷道低洼处沉淀池集中沉淀进行中级过滤分离,采用板框式压滤机进行终级过滤分离。此方法沉淀效率高,实现了清水入仓,促进了煤矿安全文明生产。

大径中厚壁管道坡口对MAG焊操作的影响

多层多道焊是核电大直径厚壁管道常用的焊接工艺,坡口形式作为影响焊道层数和道数的直接因素,不仅决定了生产成本和效率,还进一步影响着焊接过程中焊缝排道及焊枪的可操作性。采用TIG打底、MAG进行填充、盖面,分别对20°、15°和9°的U形坡口进行了试验,分析了不同坡口形式下的电弧稳定性、焊缝排道和焊枪可操作性。结果表明:坡口尺寸对电弧稳定性影响较小;15°的U形坡口既可以使电弧对坡口两侧壁进行相对充分的加热和填充,又可以保证较小的填充量,打底焊可操作性好、焊接效率高。

多煤层开采上覆采空区有害气体下泄定量化关系探讨

多煤层开采过程中上覆采空区有害气体易下泄至下伏采动空间,导致下伏开采工作面有害气体超限。以大同矿区双系煤层群开采侏罗系采空区有害气体向石炭系工作空间下泄为工程背景,应用关键层理论、流体力学等理论,提出了侏罗系采空区有害气体下泄的条件,对双系采空区连通特征进行了分类并给出其判别标准,创建了侏罗系采空区有害气体向石炭系工作面下泄的多参量控制方程。结果表明:大同矿区侏罗系煤层采空区有害气体向石炭系工作空间或采空区下泄的条件是,双系之间存在一定宽度的气体运移通道且双系流场间存在压差;大同矿区双系间采空区连通特征可以分为双系采空区流场不连通、双系采空区流场连通但不致灾、双系采空区流场连通且可致灾3类,同忻矿8207工作面与上覆侏罗系采空区的连通特征属于第Ⅲ类;针对同忻煤矿8207工作面开采条件,应用建立的有害气体下泄多参量控制方程,确定工作面主关键层破断2 h后,9403~10112 m3的有害气体从侏罗系采空区下泄到8207工作面及其采空区,从而导致8207工作面采场中有害气体2 h内增加30%~33%,易导致工作面有害气体超限。研究成果为多煤层开采上覆采空区有害气体向下伏采动空间下泄的条件、机理、下泄量计算等研究提供了全新的思路。

Study on the disaster caused by the linkage failure of the residual coal pillar and rock stratum during multiple coal seam mining:mechanism of progressive and dynamic failure

Multi-seam mining often leads to the retention of a significant number of coal pillars for purposes such as protection,safety,or water isolation.However,stress concentration beneath these residual coal pillars can significantly impact their strength and stability when mining below them,potentially leading to hydraulic support failure,surface subsidence,and rock bursting.To address this issue,the linkage between the failure and instability of residual coal pillars and rock strata during multi-seam mining is examined in this study.Key controls include residual pillar spalling,safety factor(f.),local mine stiffness(LMS),and the post-peak stiffness(k)of the residual coal pillar.Limits separating the two forms of failure,progressive versus dynamic,are defined.Progressive failure results at lower stresses when the coal pillar transitions from indefinitely stable(f,>1.5)to failing(f,<1.5)when the coal pillar can no longer remain stable for an extended duration,whereas sud-den(unstable)failure results when the strength of the pillar is further degraded and fails.The transition in mode of failure is defined by the LMS/k ratio.Failure transitions from quiescent to dynamic as LMS/k.<1,which can cause chain pillar instability propagating throughout the mine.This study provides theoretical guidance to define this limit to instability of residual coal pillars for multi-seam mining in similar mines.

多层钒矿体开采应力迁移规律和分布研究

针对多层钒矿体重叠分布、相邻矿层开采重复扰动、围岩应力分布复杂等问题,采用理论分析和数值模拟方法,建立了单层矿体矩形采空区围岩应力分布平面模型,并结合数值模拟结果,拟合了单层矿单采场采空区围岩垂直应力峰值变化率与其跨度关系式,分析了单层矿多采场围岩应力叠加特征;在此基础上,定义了双层矿体开采时采空区相对位置关系类型,研究了双层矿采空区不同跨距和垂距对其围岩应力分布特征的影响规律。研究表明:钒矿体采空区围岩存在典型的应力释放、应力跌落、应力增高和原始应力等4区分布特征,采空区跨度越大,其应力峰值越高,且应力增高区以深围岩内的应力变化率随着与应力峰值点距离的增大按照幂函数关系减小,应力跌落区内的应力变化率随着与应力峰值点距离的增大而增大;相邻采空区的应力增高区会在两者间的矿柱内叠加,矿柱内某点的应力变化率为两侧采空区分别在该点引起的应力变化率之和;当下层采空区应力释放区与上层采空区应力增高区重叠时均导致围岩内拉应力增高,当上层采空区的应力释放区与下层采空区任一区域重叠时均导致压应力降低;上下采空区重叠与非重叠区域的交汇处应力变化显著;根据多层矿体开采应力迁移规律,提出采空区强、弱扰动距,划分强扰动区、弱扰动区和无扰动区,为多层矿体开采时合理确定回采参数与回采顺序提供参考。

深埋特厚煤层多工作面开采地表移动规律研究

深埋特厚煤层多工作面开采相互影响剧烈,地表移动呈现出特殊规律。以彬长矿区文家坡煤矿41盘区4103、4104和4105工作面为例,采用数值模拟、现场实测等研究手段,探讨新工作面开采对已采工作面地表移动的影响,得出覆岩及地表应力分布特征与变化规律。研究表明:新工作面开采加剧了已采工作面地表的移动,随着新工作面开采数目的增多,已采工作面地表下沉值与水平移动值增幅逐渐变小并趋于稳定,且受相邻工作面开采影响最大。通过理论分析将深埋特厚煤层多工作面开采覆岩及地表应力划分为拉应力区、压应力区和拉压应力转化区,其中新工作面开采使老采空区覆岩产生应力扰动与面间煤柱应力集中,且覆岩压应力与面间煤柱压应力增幅程度与地表移动程度呈正相关。研究成果为深埋特厚煤层多工作面开采地表损伤预测与防治奠定基础。