A study of surface subsidence and coal pillar safety for strip mining in a deep mine

Some villages and bridges are located on the ground surface of the working district no. 7 in the Wanglou Coal Mine. If longwall mining is adopted, the maximum deformation of the ground surface will exceed the safety value. Strip mining is employed for the working district no. 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface. To ensure the safety of coal pillars and improve the recovery coefficient, theoretical analysis and numerical simulation (FLAC 3D) were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios. The results revealed that the width of coal pillars should be larger than 162 m, and the optimized mining width varies from 150 to 260 m. As the coal seam is exploited, vertical stress is mainly applied on the coal pillar, inducing stress changes on its ribs. The coefficient of mining-induced stress varies from 2.02 to 2.62 for different mining scenarios. The maximum surface subsidence and horizontal movement increase as the mining width increases. However, when the mining width increases to a certain value, increasing the pillar width cannot significantly decrease the maximum subsidence. To ensure the surface subsidence less than 500 mm, the mining width should not be larger than 200 m. Considering the recovery coefficient and safety of the coal pillar, a pillar width of 165 m is suggested.     

断裂活动影响矿区的采煤沉陷灾害问题

文章结合抚顺矿区实际,分析论述了断裂活动影响矿区的地应力环境特征。阐述了在断裂活动影响矿区,岩体长期大规模开挖造成局部区域构造应力卸载,岩体弹性变形能恢复发生水平变形,导致地表产生附加水平移动与变形。通常的沉陷区边缘区域,地表移动变形值不大,采动损害也相对较轻。但断裂活动影响矿区,沉陷区边缘区常存在着明显的水平移动与变形,并造成相应损害。尤其是在矿震等岩体地质动力现象显现影响下,地表沉陷灾害更为严重。     

New grey prediction model and its application in forecasting land subsidence in coal mine

Mining subsidence destroys environment seriously and is difficult to forecast because the parameters in prediction model are difficult to obtain. As there are many uncertainties in mining subsidence, we forecast it by grey prediction model. Traditional GM (1,1) model predict for a time series. In this paper, the panel data are studied and are viewed as a sequence in which elements are matrix based on cross-sectional data, and the mean sequence of row vector GM (1,1) model, mean sequence of column vector GM (1,1) model and the cell volume sequence GM (1,1) model are established, respectively. Combining these grey models, we build prediction model of cross-sectional data matrix sequence. Thus, the scope of grey prediction has been expanded, and grey forecasting theory has been enriched. Using the newly built predictive models, we study the land deformation due to mining of Pingdingshan coal mine in Henan Province. Practical verification and model accuracy test show that the grey model can make accurate predictions, with a good agreement between the predictive value and actual value. It can provide effective and accurate information and also can provide an important reference for the reclamation planning of surface environment.     

Research on reasonable coal pillar width of roadway driven along goaf in deep mine

Driving roadway along a goaf is commonly adopted for mining face of thick seam in a deep mine. Determining a reasonable width of coal pillar is a key scientific problem for driving roadway along a goaf in a deep mine. The paper took a roadway driven along a goaf at Zhaolou coal mine which is a typical kilometer-deep mine in China as engineering background. Field monitoring, model test, and numerical experiment are conducted. Stress and displacement evolution mechanism are analyzed with different pillar widths. The test results show that with the increase of coal pillar width, the peak stress value at the coal pillar working slope and integrated coal beside the roadway increases firstly and then tends to be stable, its position is transferred to the side of the roadway, and the deformation of coal pillar decreases gradually during roadway excavation. The coal pillar deformation and roadway vertical displacement increased as the coal pillar width increases under high abutment pressure. In order to reduce the waste of non-renewable resources and meet the requirements of bearing capacity and stability of coal pillars, a method is proposed for setting a reasonable width of coal pillars and the specific width of coal pillars is designed and applied in engineering practices based on the above research. All the tests are significant in the study of driving roadway along a goaf in a deep mine.     

东庞矿突水陷落柱三维地震处理效果与对比

以东庞矿2903工作面突水陷落柱为例,利用三维地震的纵横剖面、联井剖面、等时切片与沿层切片对陷落柱进行了对比解释,并对偏移速度90%、95%和103%的3个不同地震数据体上陷落柱边界的控制效果进行了分析。结果表明:偏移速度95%的地震处理效果较好,地震沿层属性切片技术对陷落柱的解释精度最高。     

Assessment of ground subsidence hazard near an abandoned underground coal mine using GIS

This study constructs a hazard map for ground subsidence around abandoned underground coal mines (AUCMs) at Samcheok City in Korea using a probability (frequency ratio) model, a statistical (logistic regression) model, and a Geographic Information System (GIS). To evaluate the factors related to ground subsidence, an image database was constructed from a topographical map, geological map, mining tunnel map, Global Positioning System (GPS) data, land use map, lineaments, digital elevation model (DEM) data, and borehole data. An attribute database was also constructed from field investigations and reports on the existing ground subsidence areas at the study site. Nine major factors causing ground subsidence were extracted from the probability analysis of the existing ground subsidence area: (1) depth of drift; (2) DEM and slope gradient; (3) groundwater level, permeability, and rock mass rating (RMR); (4) lineaments and geology; and (5) land use. The frequency ratio and logistic regression models were applied to determine each factor’s rating, and the ratings were overlain for ground subsidence hazard mapping. The ground subsidence hazard map was then verified and compared with existing subsidence areas. The verification results showed that the logistic regression model (accuracy of 95.01%) is better in prediction than the frequency ratio model (accuracy of 93.29%). The verification results showed sufficient agreement between the hazard map and the existing data on ground subsidence area. Analysis of ground subsidence with the frequency ratio and logistic regression models suggests that quantitative analysis of ground subsidence near AUCMs is possible.     

淮南潘一矿采煤塌陷积水区水环境健康风险评估

以淮南潘一矿塌陷积水区为例,分析测试了塌陷积水区12个采样点水样中的7种重金属元素（Cr、Cd、Zn、Cu、Pb、Ni和Fe）的含量,采用美国环保局（USEPA）推荐的水环境健康风险评价模型,对重金属由食入途径进入人体所引起的健康风险进行评估和分析。研究发现,研究区水体中重金属致癌风险值为（5.06~8.06）×10^-6/a,根据我国环境保护部推荐的健康风险标准,存在健康风险。其中,Cr的致癌风险占总致癌风险的98.52%。非致癌健康风险值在10^-10/a的数量级,健康风险不明显,而非致癌健康风险的贡献大小顺序为,Cu > Pb > Fe > Cr > Cd > Ni > Zn。其中,Cu的贡献率最大,占非致癌总风险值的48.62%。同时还发现,研究区的重金属致癌风险占总健康风险的99.99%,这表明该区域总的水质健康风险几乎全部由致癌风险构成,而致癌风险中又几乎由Cr组成。     

Mine subsidence damage from room and pillar mining in Illinois

Summary Data is presented on case histories of subsidence damage occurring over abandoned room and pillar mines in Illinois. The major modes of behaviour and damage in houses from sag-subsidence are described and summarized. The houses rested on crawl-space and basement foundations built from concrete and masonry. The prevalent mode of failure of bearing walls was inward bending. Failure is analysed and conventional design procedures are used to evaluate foundation failure.     

基于巨厚岩层-煤柱协同变形的煤柱稳定性

采前煤柱稳定性研究是工作面冲击危险性评估和开采方案设计的关键。以山东某矿深井巨厚砾岩条件工作面开采遗留煤柱为背景,采用案例调研、理论分析、数值模拟和工程实践等方法,对巨厚岩层-煤柱协同变形机制及其煤柱稳定性进行了研究,建立了巨厚岩层-煤柱协同变形的简化力学模型,探讨了引起煤柱变形的主要应力来源和变形形式,推导了在协同变形条件下煤柱的应力-应变关系。以此为基础,综合煤柱煤体应力、围岩稳定性和变形特征等条件,提出了煤柱整体失稳的力学判据。研究结果表明：巨厚岩层-煤柱失稳诱发冲击与煤柱的位置、尺寸和上覆岩层运动或变形关系密切,上覆岩层运动或变形是诱发煤柱失稳的动力因素;巨厚岩层-煤柱的变形主要包括受集中力F压迫的协同挠曲压缩变形和受集中力G作用的重力沉降变形,二者保持内在协调性;巨厚岩层下煤柱整体失稳的工程判据为煤柱煤体平均支承应力p超过其平均极限支承强度Rc（p≥Rc）;评估得到遗留的50 m煤柱具有强冲击危险性,并通过优化开采设计,取得了良好的效果。该研究成果对相似条件煤柱留设及其稳定性分析具有参考意义。     

百善煤矿含水层下留设防砂煤柱开采的地质保障系统

通过对百善煤矿十几年来中等富水性的松散含水层下留设防砂煤柱开采的实践,总结出一套确保成功开采的地质保障系统,并对该系统的各个组成部分进行定性、定量分析。指出地质保障系统是矿井优化设计、实现安全高效的前提条件和基础保证,具有巨大的决策效益和经济效益。     

Inexpensive but technically sound mine pillar design analysis

A simple algorithm (PILLR) for obtaining by two-dimensional analysis thee essential results that would be obtained in an actual three-dimensional finite element analysis of stress about mine pillars in flat-laying stratified rock is presented. A series of comparisons between the distributions of the local factor of safety calculated from the results of three-dimensional analysis and that obtained in the PILLR two-dimensional analyses for pillars of length/width ratio ranging from 0.33 to 8.0 shows the algorithm to be quite effective. The average vertical stress over the horizontal mid-plane of the pillar in the PILLR two-dimensional analyses is always within 0.5 per cent of the exact average; the local safety factor distribution is always within 10 per cent of the three-dimensional result. The ratio of the computer core x time product for the 2D' to 3D analyses is approimately 1/150. Additional improvements ard possible, although with the current PILLR algorithm 3D analyses require less than 1 minute for execution. This fact makes technically sound 3D mine pillar design analyses economically feasible on a routine basis.     

宁夏羊场湾煤矿浅埋煤层开采地面塌陷发育规律及形成机理

以宁夏羊场湾煤矿Y110207工作面为研究对象,采用无人机遥感技术、野外调查与有限差分软件模拟方法研究浅埋煤层开采的地面塌陷类型、发育规律及其形成机理。(1)浅埋煤层开采地面塌陷以地表裂缝发育为主,地表破坏严重。(2)平行切眼裂缝间隔性出现,展布于整个工作面内,间隔距离为10～120m,局部裂缝形成错台高度约为15cm。平行顺槽裂缝为拉张型裂缝,发育在顺槽至外围一定范围。(3)采煤活动导致地下形成采空区,上覆岩层发生移动破坏,破坏区分为剪切破坏区、拉张破坏区及剪-拉破坏区,分别对压应力区、拉应力区和压-拉转化区。(4)当应力扰动传递至地表,应力值超过覆盖层抗拉强度时地表产生裂缝。随着工作面推进,覆岩内部裂缝带上行裂缝与地表下行裂缝贯通,形成错台。研究成果丰富了该区浅埋煤层的地面塌陷理论知识,为地面塌陷防治提供了理论依据。     

Application of a fuzzy operator to susceptibility estimations of coal mine subsidence in Taebaek City,Korea

Quantitative determination of locations vulnerable to ground subsidence at mining regions is necessary for effective prevention. In this paper, a method of constructing subsidence susceptibility maps based on fuzzy relations is proposed and tested at an abandoned underground coal mine in Korea. An advantage of fuzzy combination operators over other methods is that the operation is mathematically and logically easy to understand and its implementation to GIS software is simple and straightforward. A certainty factor analysis was used for estimating the relative weight of eight major factors influencing ground subsidence. The relative weight of each factor was then converted into a fuzzy membership value and integrated as a subsidence hazard index using fuzzy combination operators, which produced coal mine subsidence susceptibility maps. The susceptibility maps were compared with the reported ground subsidence areas, and the results showed high accuracy between our prediction and the actual subsidence. Based on the root mean square error and accuracy in terms of success rates, fuzzy γ-operator with a low γ value and fuzzy algebraic product operator, specifically, are useful for ground subsidence prediction. Comparing the results of a fuzzy γ-operator and a conventional logistic regression model, the performance of the fuzzy approach is comparative to that of a logistic regression model with improved computational. A field survey done in the area supported the method’s reliability. A combination of certainty factor analysis and fuzzy relations with a GIS is an effective method to determine locations vulnerable to coal mine subsidence.     

Ultimate bearing capacity and settlement of coal pillar sub-strata

Summary This paper develops a rational approach for design of coal pillars under weak floor strata conditions considering ultimate bearing capacity (UBC) as well as pillar settlement. An approximate solution is presented for estimation of UBC for a shallow foundation on a two-layered rock system with consideration of both cohesion (c) and (ø) for both layers. Similarly, deformability underneath a full-size pillar is estimated from deformability calculated from plate loading tests. The effect of adjacent pillars on UBC and deformability of coal pillars in a panel is considered using foundation engineering analysis techniques. The design of pillars based on limiting settlements considers both differential settlements as well as mean settlement of pillar in a panel. An attempt is made to validate the proposed design approach based on field data and observations at an Illinois mine.     

基于四旋翼无人机的宁夏羊场湾煤矿采煤沉陷量监测

小型无人机遥感技术具有成本低、操作灵活便利等优点,在地质调查中的作用愈来愈重要。采煤地表沉陷量变形监测是掌控采煤地表岩移变形规律和治理塌陷的关键性工作。重点探索四旋翼无人机遥感技术监测在羊场湾煤矿Y120212工作面采煤沉陷量的监测研究,通过野外踏勘与控制点布设、无人机航线规划与执行、4D产品制作的工作程序和监测方法,探索无人机遥感技术监测在矿山地质塌陷监测的应用。研究结果表明,通过对无人机遥感技术生成的DSM处理,经过多期地面高程的对比,得到Y120212工作面最大沉陷量达6.5m。结合分析、对比,无人机遥感技术可以实现采煤塌陷区地表沉陷变形监测,进而形成和发展了煤矿地面塌陷新的监测技术。     

露天地下开采隔离层稳定性研究

露天地下开采隔离层稳定性分析是矿山中经常遇到的问题。以大宝山矿露天地下开采的工程实例,采用数值分析方法,对隔离层稳定性进行分析计算,发现空区顶板的拉应力是关系隔离层稳定性的关键因素。通过对隔离层的安全厚度数值计算,与5种理论计算方法结果进行了比较,综合求和归一法数据处理和多项式数值逼近得到了不同空区跨度与隔离层安全厚度关系。结果为露天地下开采隔离层稳定性分析的方法进行了验证和补充,也为矿山设计隔离层厚度提供了参考,对指导露天地下开采安全生产施工具有重要意义。     

断层防水煤柱可靠度分析

为了合理设计防水煤岩柱的宽度,使用了可靠度分析的“JC”方法,分析了水压力、煤层抗张强度及突水系数的不确定性,建立了防水煤柱可靠度分析的极限状态方程。并计算了与防水煤柱有关的可靠度指标、失效概率和安全系数。参考其它事故的死亡率,防水煤柱的失效概率为1× 10 -5~1× 10 -6比较合适。