Predicting the height of water-flow fractured zone during coal mining under the Xiaolangdi Reservoir

It is very important to determine the extent of the fractured zone through which water can flow before coal mining under the water bodies.This paper deals with methods to obtain information about overburden rock failure and the development of the fractured zone while coal mining in Xin'an Coal Mine.The risk of water inrush in this mine is great because 40%of the mining area is under the Xiaolangdi reservoir.Numerical simulations combined with geophysical methods were used in this paper to obtain the development law of the fractured zone under different mining conditions.The comprehensive geophysical method described in this paper has been demonstrated to accurately predict the height of the water-flow fractured zone.Results from the new model, which created from the results of numerical simulations and field measurements,were successfully used for making decisions in the Xin'an Coal Mine when mining under the Xiaolangdi Reservoir.Industrial scale experiments at the number 11201,14141 and 14191 working faces were safely carried out.These achievements provide a successful background for the evaluation and application of coal mining under large reservoirs.

Research of the electrical anisotropic characteristics of water-conducting fractured zones in coal seams

Water flooding disasters are one of the five natural coal-mining disasters that threaten the lives of coal miners. The main causes of this flooding are water-conducting fractured zones within coal seams. However, when resistivity methods are used to detect water-conducting fractured zones in coal seams, incorrect conclusions can be drawn because of electrical anisotropy within the water-conducting fractured zones. We present, in this paper, a new geo-electrical model based on the geology of water-conducting fractured zones in coal seams. Factors that influence electrical anisotropy were analyzed, including formation water resistivity, porosity, fracture density, and fracture surface roughness, pressure, and dip angle. Numerical simulation was used to evaluate the proposed electrical method. The results demonstrate a closed relationship between the shape of apparent resistivity and the strike and dip of a fracture. Hence, the findings of this paper provide a practical resistivity method for coal-mining production.

Height prediction of water flowing fractured zones based on BP artificial neural network

Factures caused by deformation and destruction of bedrocks over coal seams can easily lead to water flooding(inrush)in mines,a threat to safety production.Fractures with high hydraulic conductivity are good watercourses as well as passages for inrush in mines and tunnels.An accurate height prediction of water flowing fractured zones is a key issue in today's mine water prevention and control.The theory of leveraging BP artificial neural network in height prediction of water flowing fractured zones is analysed and applied in Qianjiaying Mine as an example in this paper.Per the comparison with traditional calculation results,the BP artificial neural network better reflects the geological conditions of the research mine areas and produces more objective,accurate and reasonable results,which can be applied to predict the height of water flowing fractured zones.

Stresses and Shear Fracture Zone of Jinshazhou Tunnel Surrounding Rock in Rich Water Region

Field evidence has shown that large-scale and unstable discontinuous planes in the rock mass surrounding tunnels in rich water region are probably generated after excavation. The tunnel surrounding rock was divided into three zones, including elastic zone, plastic damage zone and shear fracture zone for assessing the stability of the tunnel surrounding rock. By local hydrogeology, the stresses of surrounding rock of Jinshazhou circular tunnel was analyzed and the stress solutions on the elastic and plastic damage zones were obtained by applying the theories of fluid-solid coupling and elasto-plastic damage mechanics. The shear fracture zone generated by joints was studied and its range was determined by using Molar-Coulomb strength criterion. Finally, the correctness of the theoretical results was validated by comparing the scopes of shear fracture zones calculated in this paper with those from literature.

Height Detection and Analysis of Water Flowing Fractured Zone of Coal Face

Taking 91105 working face as the research object, the observation method of water flowing fractured zone and the layout of mining holes were determined by analyzing the field geological structure. It was shown that the fractured zone height and the ratio given by the measured method were 52.33 and 12.46, respectively. By the numerical simulation method with the software of UDEC, the fractured zone height and the ratio were 42.5 and 10.12. By comparison of measured height data and UDEC numerical simulation, there were some differences between the measured height and the calculated results of UDEC numerical simulation method. The method of simulation can be used as the technical basis for the design of waterproof coal pillar in the future.

Fractured zone height of longwall mining and its effects on the overburden aquifers

As mining depth becomes deeper and deeper,the possibility of undermining overburden aquifers is increasing.It is very important for coal miners to undertake studies on the height of fractured zone during longwall mining and the effects of longwall mining on the underground water while mining under surface water bodies and underground aquifers.In order to study this problem,piezometers for monitoring underground water levels were installed above the longwall panels in an American coalmine.Large amounts of pre-mining,during mining and post-mining monitoring data were collected.Based on the data,the heights of fractured zones were obtained and the effects of longwall mining on the underground water were studied.The results demonstrate that when the piezometer monitoring wells had an interburden thickness of less than 72.7 m,the groundwater level decreased immediately to immeasurable levels and the wells went dry after undermining the face of longwall.The height of the fractured zone is 72.7-85.3 m in the geological and mining conditions.The results also show that the calculated values of fractured zones by the empirical formulae used in China are smaller than the actual results.Therefore,it is not always safe to use them for analyses while mining under water bodies.

Forecasting water disaster for a coal mine under the Xiaolangdi reservoir

Xin’an coal mine, Henan Province, faces the risk of water inrush because 40% of the area of the coal mine is under the surface water of the Xiaolangdi reservoir. To forecast water disaster, an effective aquifuge and a limit of water infiltration were determined by rock-phase analysis and long term observations of surface water and groundwater. By field monitoring, as well as physical and numerical simulation experiments, we obtained data reflecting different heights of a water flow fractured zone (WFFZ) under different mining conditions, derived a formula to calculate this height and built a forecasting model with the aid of GIS. On the basis of these activities, the coal mine area was classified into three sub-areas with different potential of water inrush. In the end, our research results have been applied in and verified by industrial mining experiments at three working faces and we were able to present a successful example of coal mining under a large reservoir.

Analysis of the Mechanism of Water Inrush Geohazards in Deep-Buried Tunnels under the Complex Geological Environment of Karst Cave-Fractured Zone

To study the mechanism and evolution process of water inrush geohazards under the complex geological environment of the karst cave-fractured zone,a large-scale physical threedimensional(3 D)model test was first performed.Then the conceptual model for the evolution process of water inrush geohazards and the simplified theoretical model for the critical hydraulic pressure were both established based on the main characteristics of the water inrush geohazard in the engineering background and that in the model test.A new method was developed for modeling the geological environment of the karst cave-structural plane,and two formulae describing the critical water pressure of water inrush geohazards under two failure models of tensile-shear fracture failure and compressionshear fracture failure were also deduced based on fracture mechanics.The results showed that:(1)the evolution process of the water inrush geohazard can be divided into four stages,which include the initial balance,the propagation of original cracks,the formation of the dominant water inrush channel,and the instability of the waterproof rock mass;(2)the suddenness of water inrush geohazards becomes stronger with the increase of the hydraulic pressure;(3)the calculated critical hydraulic pressure of water inrush geohazards is similar to the measured critical hydraulic pressure in the model test,which validated the accuracies of the theoretical model,and the failure model of water inrush geohazards in this research is compression-shear fracture failure.

Optimum Calculation of Coal Pillars in Inclined Weathered Oxidation Zone

In the mining process of coal mine,waterproof coal pillars should be set between the weathered oxidation zone and the first mining face.In order to determine the reasonable upper limit of the first mining face of Hongyi Coal Mine,the waterproof coal pillar needs to be wide enough to resist the lateral hydrostatic pressure of the oxidation zone,and to ensure that the top plate aquifer does not run through the water guide crack zone,while also liberating as much stagnant coal as possible.In this paper,the first coal mine face’s waterproof coal pillar was calculated using conventional and optimized calculation methods,taking into account the dip angle of the coal seam,the height of the water-guide crack zone,and the rock shift influence zone,and finally the upper limit of the first face of Hongyi Coal Mine was determined.

覆岩导水裂隙带发育高度动态演化规律研究

为了研究覆岩导水裂隙带发育高度动态演化规律,以小保当矿区2^(-2)煤层为研究对象,通过理论分析、相似模拟实验及实例验证的方法,对导水裂隙带动态发育高度进行研究;借助概率积分法预计其上部岩层移动变形的理论公式,给出了1种基于覆岩曲率变形的导水裂隙带动态发育高度预计方法。研究表明:导水裂隙带上部岩层下沉系数是1个与挠度及下部自由空间高度相关的分段函数,上部岩层曲率变形大小是决定导水裂隙带发育高度的关键因素;导水裂隙带发育高度与工作面推进长度相关;理论预计小保当矿区2^(-2)煤层导水裂隙带发育高度为160.8 m,相似模拟实验发育高度为155 m,现场实测发育高度为152.01~175.57 m。

考虑采动效应的闭坑矿井水硫酸盐污染规律

高硫煤矿闭坑后成为埋藏在地表以下深部的产酸污染场,对相邻含水层和周边环境造成了潜在危害,且因采动效应影响和矿井空间分布复杂导致相邻含水层的污染过程与污染程度评价困难。以某闭坑矿区为研究对象,选取SO_(4)^(2-)作为特征污染物,考虑多煤层采动裂隙对含水层结构的破坏影响,运用数值模拟技术对闭坑矿区酸性矿井水中SO_(4)^(2-)污染迁移特征进行研究,并分析流体扩散系数对含水层污染物运移的影响。结果表明:SO_(4)^(2-)在二叠系童子岩组砂岩含水层中水平迁移面积随时间增大而增大,增大速率逐渐减小,垂向渗透系数扩大10倍,空间变异性增强;闭坑5、10、15a后,最大水平迁移距离分别为215、414、612m,最大垂向迁移距离分别达到50、65、70m;而扩散系数越大,产酸时间越长,SO_(4)^(2-)迁移距离和污染范围将随之增大,相较于水平方向,垂向上SO_(4)^(2-)浓度变化对扩散系数的敏感度更高。基于模拟结果,结合闭坑矿区实际条件,针对性提出了“源头减量-过程阻断-末端治理”的综合防控与治理方案。研究结果将为该闭坑煤矿酸性矿井水污染治理与防控提供理论基础,也为其他同类矿井提供科学借鉴。

王洼煤矿水库坝体下工作面安全开采高度研究

为解决水库坝体下开采安全性,提高煤炭资源回收率,以王洼煤矿水库坝体下110505工作面为研究背景,通过物理仿真模拟、数值模拟及理论分析等方法对覆岩裂隙发育规律及导水裂隙带高度展开研究。为避免矿井开采对地表水坝与水体破坏,针对导水裂隙带高度分析结果,提出了110505工作面限高开采方案。结果表明:工作面开采后地表形成“凹”型盆地,并产生拉伸裂隙,致使地表水位下降78%;现场实测导水裂隙高度为170.76 m,物理仿真模拟试验、数值计算、传统经验公式得出三者的导水裂隙带高度分别为162,164 m和120.57 m;方差修正系数对经验公式做出修正后,反推出限高开采的安全开采高度为2.6 m。研究揭示了工作面覆岩导水裂隙带高度发育规律及水库水体受采动影响的规律,为王洼煤矿后续此类条件下安全措施的制定提供了依据。

隧道富水断层破碎带突涌预报与工程对策研究

为解决高原隧道断层破碎带易发突泥冒顶灾害的问题,采用现场调查、地面物探、洞内地震波反射法、瞬变电磁法、超前钻孔等超前地质预报方法,推广洞内物探三维分析,对富水断层破碎带突泥灾害特征、超前地质预报综合成果和工程应对加固措施进行研究。结果表明:三维物探成果能快速精准查明富水破碎带空间形态,成果直观,有效指导风险判识和工程处置措施;对富水断层带预报应充分结合勘察期成果,宏观初判断层分布特性,洞内采用物钻结合、长短结合的方法;首次提出按照“探明破碎带规模形态,查明破碎带物质组分性状,观测地下水特征变化情况”的思路,研判突泥涌水风险;施工处置应按照“探泄结合,先固后进,回堵再泄”的总体原则有序开展。研究成果和手段可为类似突涌灾害超前地质预报和工程应对措施提供参考。

综采工作面采动覆岩导水裂隙带发育高度综合研究

针对因煤层开采易导致上覆岩层产生裂隙,贯通地下含水层引发矿井水灾的问题,以盘城岭煤业150105工作面为研究背景,采用理论公式、现场井下仰孔注水测漏法和钻孔电视成像探测法,以及FLAC3D和UDEC数值模拟综合分析导水裂隙带的高度和发育规律。理论计算导水裂隙带的最大高度为81.56 m;通过井下仰孔注水测漏法监测3个钻孔的注水渗透量梯度临界值为12 L/min,通过临界值判定导水裂隙带高度为78.56~79.99 m;通过钻孔电视成像探测法观测钻孔内裂隙分布判定导水裂隙带高度为78.39~79.46 m;利用FLAC3D和UDEC数值模拟,根据覆岩塑性区变化特征,当工作面推进至180 m时,裂隙发生贯通,塑性区最大高度达到76.4 m,并根据覆岩塑性区变化、垂直应力分布、垂直位移云图分析了导水裂隙带发育规律的3个阶段。对不同方法下的导水裂隙带高度进行了相互验证。

鲁中南典型地热区地热水氟分布特征及其驱动机制

山东省鲁中南典型地热区主要包括沂沭断裂带地热区和鲁中隆起地热区,为了探明研究区地热水氟分布特征及其富集规律,综合运用水化学图解、地球化学模拟和主成分分析等方法,分析沂沭断裂带地热区和鲁中隆起地热区地热水水化学数据。结果表明:研究区地热水以Na-Ca-Cl型、Na-Ca-SO_(4)-Cl型和Na-Cl^(-)SO 4型为主,基本为弱碱性水,优势阳离子为Na^(+),氟质量浓度在0.38~4.5 mg/L之间,富钠弱碱性环境有利于地热水中氟的富集。地热水中F-质量浓度与Na^(+)、Cl^(-)和总溶解固体(TDS)质量浓度呈显著正相关,而沂沭断裂带地热水样中F-质量浓度还与K^(+)、SO_(4)^(2-)质量浓度呈显著正相关,与Mg^(2+)和HCO_(3)质量浓度呈显著负相关;鲁中隆起地热区地热水中阳离子交换作用较沂沭断裂带地热区更为强烈,Na^(+)反应强度明显强于Mg^(2+)。鲁中隆起地热区和沂沭断裂带地热区均为裂隙型热储,热储岩性分别为石灰岩、灰岩热蚀变带和安山岩破碎带,水岩作用强烈。研究区地热水中氟离子的物质来源主要为萤石等含氟矿物的溶解沉淀,受控于阳离子交换等水岩相互作用影响,最终形成高氟地热水,其中高温和富钠对研究区地热水中氟离子富集影响较大。研究成果为地热资源开发利用提供了参考。

基于相似模拟试验的顶板导水裂隙带高度及发育形态研究

目的 为研究采动影响下顶板导水裂隙带高度及其发育形态,方法 以司马煤矿三采区1303工作面为研究对象,开展相似模拟试验,并以此为基础,对顶板的岩性组合加以改变,结合数字照相量测系统对不同岩性组合顶板导裂带高度和发育形态进行分析,并进行理论验证。结果 结果表明:(1)工作面推进长度为160 m时,硬岩岩性顶板模型、硬-软岩岩性组合顶板模型以及软岩岩性顶板模型的导水裂隙带最大发育高度分别为69.6,55.6,61.1 m;(2)3种模型的导水裂隙带发育形态分别为底角50°的正梯形、前底角62°后底角60°的近似正梯形、前底角50°后底角60°的梯形;(3)根据模型试验和数据统计结果,给出适用于长治二岗山断褶带以南井田导水裂隙带发育高度预测式;(4)运用材料力学方法分析垮落角形成规律,垮落角与导水裂隙带发育高度呈反正切函数关系,并计算得到3种模型导水裂隙带前底角发育角度,分别为49.24°,61.21°和51.12°。通过导高计算公式得到3种模型导水裂隙带发育高度分别为74.1,51.1,59 m,均与相似模拟试验结果吻合。结论 研究结果对各类岩性顶板煤矿导水裂隙带发育高度预测具有参考意义。

深埋煤层开采对河流安全性的影响评价

以文家坡煤矿4105工作面深埋覆水煤层开采为例,采用相似材料模拟和数值模拟方法,研究覆岩破坏和裂隙带发育规律,探究深埋煤层开采对红岩河安全的影响。研究表明:当工作面不断推进,采空区面积随之增加,覆岩在重力作用下发生弯曲变形,形成离层;当重力超过岩石变形极限时,覆岩会破坏变形,部分离层垮落消失,在垮落体上部发育新离层,两侧形成裂隙;4105工作面垮落带高度稳定在164 m;随着工作面的不断推进,导水裂隙带高度逐步上升,最终稳定在244 m;地裂缝自地表向下延伸32 m;导水裂隙带上方存在414 m的岩层做保护层,未导通地表,未与地裂缝沟通,因此红岩河不会发生渗漏,煤层的开采不会对红岩河产生影响。

在役岩溶隧道衬砌水压分布及预警控制标准研究

随着强降雨天气的频发,在役岩溶隧道衬砌开裂、渗漏水及失稳破坏事故日益增多。地表降雨补给下衬砌背后积聚高水压力是岩溶隧道发生水压灾害的主要原因,对在役岩溶隧道开展监测预警是避免灾害发生的重要手段。以郑万线岩溶隧道为依托,开展了相似模型试验及渗流数值模拟,研究了不同岩溶形态下衬砌背后水压分布规律及衬砌隆起位移,制定了岩溶隧道运营监测预警控制标准。结果表明:当地表降雨补给超过隧道排水能力时,衬砌背后将形成“地表补给+洞内排水”的动水压力,仰拱底部极易积聚高水压力;地层中存在岩溶管腔和溶蚀裂隙带时,地表降雨将会导致衬砌水压局部增高,衬砌承受偏压荷载,并使仰拱受力进一步劣化;以隧道仰拱中心水压力和隆起位移作为控制基准,将岩溶隧道运营监测预警等级划分正常运营、临时补修、限速整治和封闭整治。研究成果可为岩溶隧道的结构设计优化及监测预警提供借鉴。

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。

大采宽综采工作面导水裂隙带高度探究

为了探究永煤公司新桥煤矿深埋煤层大采宽工作面导水裂隙带高度发育特征,以典型的开采宽度330 m的某工作面为研究对象,建立了深埋煤层大采宽工作面三维工程地质概化预开采模型,采用FLAC3D数值模拟软件对采动覆岩导水裂隙带高度进行研究,发现这种大采宽工作面开采后应力集中程度明显增大。和经验公式类比获得了该工作面导水裂隙带高度取值范围,提出了现行规范中的相关计算公式预计结果明显偏小,已不适合这种地质及开采条件。最后,在其他条件不变仅改变采宽条件下,模拟了7种不同采宽开采后沿倾向和走向导水裂隙带高度发育特征,对比分析发现导水裂隙带高度随采宽增加呈非线性变化,两者之间具有很好的自然对数拟合关系,确定了增加幅度的采宽阈值及其变化特征。