An Analysis of Chamber Filling Effects on the Remediation of Flooded Gypsum and Anhydrite Mines

Summary  Abandoned gypsum and anhydrite mines can be filled by underground water that progressively dissolves pillar rock. The long term stability of the mine under the weight of the overburden is therefore jeopardised. A common remedial measure consists in filling the flooded chambers with granular materials. The aim of the paper is that of investigating the effect of the mechanical characteristics of the filler on the time of mine collapse, induced subsidence and pore water pressure generation. By means of Sharp Front theory the saturation front advance and the loss of pillar bearing capacity with time is determined first. Subsequently one dimensional consolidation theory is used for the determination of the proportion of overburden weight carried by the solid skeleton of the filler and by water pressure. A parametric analysis is eventually performed for the case of an abandoned gypsum and anhydrite mine in order to determine the most appropriate mechanical characteristics of the filler material. Author’s address: Eleni Gerolymatou, Department of Applied Mathematics and Physics, National Technical University of Athens, 9 Iroon Politechneiou Street, 15780 Athens, Greece     

关闭/废弃矿井地下空间资源精准开发利用模式研究

随着煤炭绿色资源的不断开采,位于煤炭开发利用全周期末端的矿井关闭\废弃问题逐渐显现,随之而来的关闭/废弃矿井地下空间资源开发利用成为一个亟须解决的问题。在对我国废弃矿井现状统计分析的基础上,以能源开采造成的地下空间方位、形态差异化为依据,将关闭/废弃矿井地下空间资源分为采空区空间资源、巷道空间资源、硐室空间资源;探讨了空间资源作为能源存储场所的单一利用方式和多方向、多领域协同多元开发利用的关闭/废弃矿井地下空间资源利用方式;并由此提出了一种关闭/废弃矿井地下空间分类分级精准利用模式,构建调研分析、工程类比初判、模型构建详估和软件决策系统研发为主干流程的精准开发利用系统,通过精准利用模式与精准开发利用系统模型对单一和多元开发利用方式进一步分析,为关闭/废弃矿井空间资源开发利用的研究和实践提供参考。      

石膏矿岩水致老化效应试验

为研究石膏岩的水致老化效应,在室内模拟石膏矿采空区的水环境条件,包括不同空气湿度环境和饱和地下水环境。将石膏岩岩样置于其中,定期取出测定其力学性质指标,得到石膏岩老化的宏观力学表现,并结合核磁共振技术测定试验过程中石膏岩岩样内部的孔隙结构变化,分析石膏岩的水致老化机制。研究结果表明,水对石膏岩的老化效应具有显著的影响。老化程度随时间递增,石膏岩的单轴抗压强度、巴西抗拉强度和弹性模量与置于水环境中的时间基本呈负指数关系,泊松比则无明显变化规律;石膏岩老化程度和老化速率与水的状态密切相关。相对湿度越高,石膏岩的老化越显著,老化速率也更快,尤其是被液态水浸泡时,石膏岩的老化最显著,老化速率最快。水对石膏岩的老化过程是水的物理作用与化学作用的耦合,而化学作用是水致石膏岩老化的根本原因。石膏岩与水接触时,石膏的溶解、重结晶作用的不断进行改变着石膏岩的矿物组成结构,使其结构由紧密变得松散,孔隙率增大,力学性质不断弱化。该试验研究结果可为石膏矿开采的设计及采后空区的长期稳定性评估提供参考。     

A method to mitigate acid-mine drainage in the Shamokin area,Pennsylvania, U.S.A.

The three anthracite coal fields of eastern Pennsylvania occur in large synclinal basins surrounded by sandstone hogback ridges. The streams draining the coal regions are heavily contaminated by sulfuric acid due to the weathering of pyrite in the abandoned mines and culm. Dams could be built in the water gaps of the streams leaving the basins, forming huge reservoirs. For example, in the western part of the Middle Coal Field (Shamokin-Mt. Carmel area), the construction of four dams would form a reservoir that would inundate practically all the culm banks, abandoned mines, and environmentally abused lands in this coal field. The reservoir (at approximately 410 m elevation) would be approximately 140 sq km in area and could be the source of water for pumped-storage hydroelectricity generation. The water should have moderately good quality and could serve the recreational needs of a vast population of the Middle Atlantic states.     

Development of thermodynamically-based models for simulation of hydrogeochemical processes coupled to channel flow processes in abandoned underground mines

Accurate modeling of changing geochemistry in mine water can be an important tool in post-mining site management. The Pollutant Sources and Sinks in Underground Mines (POSSUM) model and Pollutant Loadings Above Average Pyrite Influenced Geochemistry POSSUM (PLAYING POSSUM) model were developed using object-oriented programming techniques to simulate changing geochemistry in abandoned underground mines over time. The conceptual model was created to avoid significant simplifying assumptions that decrease the accuracy and defensibility of model solutions. POSSUM and PLAYING POSSUM solve for changes in flow rate and depth of flow using a finite difference hydrodynamics model then, subsequently, solve for geochemical changes at distinct points along the flow path. Geochemical changes are modeled based on a suite of 28 kinetically controlled mineral weathering reactions. Additional geochemical transformations due to reversible sorption, dissolution and precipitation of acid generating salts and mineral precipitation are also simulated using simplified expressions. Contaminant transport is simulated using a novel application of the Random-Walk method. By simulating hydrogeochemical changes with a physically and thermodynamically controlled model, the ‘state of the art’ in post-mining management can be advanced.     

废弃煤矿瓦斯资源估算与评价方法构建及应用

基于我国废弃煤矿瓦斯资源勘探开发现状,为合理评估我国废弃煤矿瓦斯资源,提出"资源估算+初步评价"的思路,建立废弃煤矿瓦斯资源估算和评价方法,该方法具有所需参数少和实用性强等优点;依据废弃煤矿瓦斯涌出特点及废弃时间,划分废弃煤矿类型,将其分为稳定型和非稳定型两大类,非稳定型进一步划分为初期、中期和后期3个阶段;根据废弃煤...     

黄河流域九省区废弃矿井抽水蓄能利用潜力评估

针对我国关闭矿井资源利用率低、蓄电储能需求日益增长的问题,废弃矿井抽水蓄能技术是实现资源二次开发利用,提升电网调峰能力的有效手段。基于废弃矿井抽水蓄能电站工作原理与发展现状,提出在黄河流域九省区利用废弃矿井建设抽水蓄能电站的半地下式、全地下式2种模式。通过综合考虑空间、地质、水文、社会、经济与资源等影响因素,提出废弃矿井抽水蓄能电站选址评价指标体系,并进行黄河流域废弃矿井抽水蓄能电站实例分析。基于2016—2020年黄河流域九省区的废弃煤矿资料,利用废弃矿井抽水蓄能电站静态效益与动态效益计算方法,定量评估黄河流域九省区废弃煤矿抽水蓄能电站建设的开发潜力。结果表明:(1) 黄河流域九省区能源资源丰富,现阶段满足电力供应需求,但火电仍是电力供应主体且水电发展进入瓶颈阶段;(2) 影响废弃矿井抽水蓄能电站选址的重要因素为巷道空间体积、上下水库水位差、巷道围岩稳定性、巷道围岩渗透率与地下水循环特征;(3) 由黄河流域废弃矿井抽水蓄能电站实例分析可知,其发电效率可达到75.7%,可媲美常规抽水蓄能电站;(4) 2016—2020年黄河流域九省区废弃煤矿累计有效可利用井巷空间为4.7×107 m3,依据132座废弃矿井基本情况,从统计学角度估算出废弃矿井抽水蓄能电站可利用井巷空间为1.34×107 m3,利用其建设抽水蓄能电站年发电量可达3.78×109 kW·h,可满足2021年黄河流域九省区28.4%的弃风、弃光电量的消纳需求,每年直接经济效益约达21.2亿元。综上表明,黄河流域九省区废弃矿井抽水蓄能利用具有可观的发展前景。      

废弃矿井地下空间旅游资源开发利用模式研究

随着煤炭产业去产能政策的深入推进,大量矿井面临关闭或废弃,但其仍赋存大量可利用资源,如何开发利用,已成为煤炭工业转型发展的一大难题。在分析国内废弃矿井工业旅游开发现状与地下空间旅游开发问题的基础上,借鉴学习国外废弃矿井旅游开发模式经验,并总结分析废弃矿井地下空间旅游资源的特征。探索废弃矿井地下空间旅游资源开发利用模式,提出基于视觉、触觉和听觉以及知识性、观赏性、参与性、娱乐性和趣味性的“三觉五性”设计方法。并针对目前废弃矿井地下空间资源开发利用中存在的问题,给出相应的对策,即:高度重视废弃矿井旅游资源开发,改善传统单一旅游模式,加强体验式旅游设计,对地下空间进行现代化功能型改造。对实现地下空间资源利用最大化,服务于国家发展建设、社会民生保障及经济发展提供一定参考。      

The emissions of gases from abandoned mines: role of atmospheric pressure changes and air temperature on the surface

Intrinsic parameters influence abandoned mine gas emissions. Independent of the presence or not of noxious gas in mine voids, meteorological factors influenced directly the gas outflow or inflow. Measurement stations were installed in the exits located in abandoned mines of the iron Lorraine basin, the Lorraine and the north east France coal basins to enhance the gas flow behaviour. Closure methods of the mines and exits from the abandoned mines are quite different. For the first, shafts are associated with adits. Some of them are closed with bars to avoid people entrance into abandoned mine workings, but gas flow is enabled. For the second, there are essentially shafts which are secured. Some of them are equipped with a vent to enable outflow of the mine gas in specific conditions. Mine gas parameters were measured. Besides, external parameters like temperature and atmospheric pressure were monitored. Gas flow can be influenced mainly by the temperature difference between external atmosphere and mine workings (in iron mines, which can be considered as an open system) while atmospheric pressure influences gas flow in the coal mines, which can be considered as closed systems. Modelling has confirmed the differential pressure value measured that exceeds friction losses.     

Ennoyage des mines de fer lorraines : impact sur la qualité de l'eau

The flooding of the abandoned iron mines of Lorraine leads to a degradation of the groundwater quality. Laboratory experiments allowed us to build a kinetic chemical model based on simple chemical mechanisms. During mining operations, pyrite oxidation and carbonate dissolution lead to the precipitation of gypsum. The local decrease of pH favours local dissolutions of minerals and releases ions that are fixed on cationic exchange sites. During the flooding of the mine workings, the dissolution of the newly precipitated gypsum, the precipitation of carbonates and cationic exchange reactions are responsible for the increase of the concentrations of sulphate, magnesium, sodium, potassium and strontium in water. Thereafter, these concentrations would decrease with the natural leaching of the mining reservoir. To cite this article: P. Collon et al., C. R. Geoscience 336 (2004).     

The Oued Mellègue: Mining activity,stream sediments and dispersion of base metals in natural environments,North-western Tunisia

In the Northwest of Tunisia, mining works have occurred in an area of vital water reserves and resources (Oued Mellègue and Oued Mejerda), which represent nearly 81% of total potential of water in the region. Demographic growth, insufficient drinkable water, agriculture and industrial plants are factors responsible for the strong demand of this resource. Water supply is done by an interconnected battery of dams built on the major watercourses, the first of which, the Mellègue dam, was erected in the 1960s. Nowadays, most of the mines are closed for almost two decades although one is still active: (Jerissa for Fe). It is important to emphasise the fact that there are millions of cubic metres of abandoned tailings, mainly from Pb–Zn–Ba mines, which are not surveyed, representing a serious threat to the environment.     

Controls on the chemistry of springs at Teels Marsh,Mineral County,Nevada

Evaporative process plays a dominant role in determining the water chemistry of the springs at Teels Marsh, a closed basin in western Nevada. Analysis of the spring waters indicates that calcium, magnesium, sulfate, and silica are removed from solution during dry periods, even though groundwater is undersaturated with respect to gypsum, amorphous silica, and sepiolite. The removal mechanism is precipitation of authigenic phases such as gypsum above the water table, in the vadose zone.In episodes of rain and snowfall in which none of the waters enters the phreatic zone, ions in the rain and snow accumulate near the ground surface. This accumulation of material, together with the sparse rain and snowfall, inhibits chemical weathering of silicate minerals. Only at high elevations in the basin is there sufficient fluxing of water through the alluvium for silicate weathering to make a significant contribution to the sodium content of the springs. When a sufficiently heavy rainfall occurs, salts are partially dissolved and the ions transported to the permanent groundwater. The kinetics of dissolution of secondary phases in the vadose zone exert an important control on the composition of the springs.     

第三系红层中石膏溶蚀特性及其对工程的影响

第三系红层中石膏分布比较广泛,大量的实验证明,石膏发生溶蚀的主要是含Ca2 的物质,并且溶蚀速率和与水接触的方式以及水头压力大小有直接关系。结合现场资料,将渗透系数K=10-5cm s作为石膏在第三系红层泥岩封闭下发生溶蚀的判据。同时针对水利工程中石膏溶蚀以及对砼的腐蚀性提出了相应的防治措施。     

Discovering the stone heritage of southern Italy: technical properties of the Mondragone marble from Campania region

The results of the geological characterization of an old stone building in southern Italy, are presented here. The Mondragone marble is a slightly metamorphosed carbonate rock, which was widely employed as monumental stone in the 18th century Royal Palaces of Naples and Caserta. In this paper, for the first time, this rock has been investigated with a thorough laboratory testing program, aimed at defining its mineralogical, physical and mechanical parameters. The two most important varieties of Mondragone marble were separately tested: the yellow and grey marbles (hereafter, YM and GM, respectively). The results obtained from physical tests (open porosity, dry density, specific gravity, water absorption coefficients, ultrasonic velocity) did not show marked differences between the two materials; in contrast, the mechanical strength tests (uniaxial compressive strength, point load strength, flexural strength) showed better behaviour of YM than for GM. After a tentative comparison with other well known carbonate rocks from Italy, some considerations on the response of Mondragone marble to local weathering were conducted. In particular, the weathering typologies were related to the particular texture of the brecciated marble and the different strength resistances displayed by the various constituents of the rock.     

Geochemistry and stable isotope investigation of acid mine drainage associated with abandoned coal mines in central Montana,USA

The Great Falls-Lewistown Coal Field (GFLCF) in central Montana contains over 400 abandoned underground coal mines, many of which are discharging acidic water with serious environmental consequences. Areas of the mines that are completely submerged by groundwater have circum-neutral pH and relatively low concentrations of metals, whereas areas that are only partially flooded or freely draining have acidic pH (< 3) and high concentrations of metals. The pH of the mine drains either decreases or increases after discharging to the surface, depending on the initial ratio of acidity (mainly Al and Fe²⁺) to alkalinity (mainly HCO₃^?). In acidic, Fe-rich waters, oxidation of Fe²⁺ after exposure to air is microbially catalyzed and follows zero-order kinetics, with computed rate constants falling in the range of 0.97 to 1.25 mmol L^? 1 h^? 1. In contrast, Fe²⁺ oxidation in near-neutral pH waters appears to be first-order with respect to Fe²⁺ concentration, although insufficient data were collected to constrain the rate law expression. Rates of Fe²⁺ oxidation in the field are dependent on temperature such that lower Fe²⁺ concentrations were measured in down-gradient waters during the day, and higher concentrations at night. Diel cycles in dissolved concentrations of Zn and other trace metals (Mn, Ni) were also noted for down-gradient waters that were net alkaline, but not in the acidic drains.The coal seams of the GFLCF and overlying Cretaceous sandstones form a perched aquifer that lies ~ 50 m above the regional water table situated in the underlying Madison Limestone. The δD and δ¹⁸O values of flooded mine waters suggest local derivation from meteoric water that has been partially evaporated in agricultural soils overlying the coal mines. The S and O isotopic composition of dissolved sulfate in the low pH mine drains is consistent with oxidation of biogenic pyrite in coal under aerated conditions. A clear distinction exists between the isotopic composition of sulfate in the acid mine waters and sulfate in the adjacent sedimentary aquifers, making it theoretically possible to determine if acid drainage from the coal mines has leaked into the underlying Madison aquifer.     

Using stable isotopes (δD, δ<Superscript>18</Superscript>O, δ<Superscript>34</Superscript>S and <Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr) to identify sources of water in abandoned mines in the Fengfeng coal mining district,northern China

With depleted coal resources or deteriorating mining geological conditions, some coal mines have been abandoned in the Fengfeng mining district, China. Water that accumulates in an abandoned underground mine (goaf water) may be a hazard to neighboring mines and impact the groundwater environment. Groundwater samples at three abandoned mines (Yi, Er and Quantou mines) in the Fengfeng mining district and the underlying Ordovician limestone aquifer were collected to characterize their chemical and isotopic compositions and identify the sources of the mine water. The water was HCO₃·SO₄-Ca·Mg type in Er mine and the auxiliary shaft of Yi mine, and HCO₃·SO₄-Na type in the main shaft of Quantou mine. The isotopic compositions (δD and δ¹⁸O) of water in the three abandoned mines were close to that of Ordovician limestone groundwater. Faults in the abandoned mines were developmental, possibly facilitating inflows of groundwater from the underlying Ordovician limestone aquifers into the coal mines. Although the Sr²⁺ concentrations differed considerably, the ratios of Sr²⁺/Ca²⁺ and ⁸⁷Sr/⁸⁶Sr and the ³⁴S content of SO₄^2? were similar for all three mine waters and Ordovician limestone groundwater, indicating that a close hydraulic connection may exist. Geochemical and isotopic indicators suggest that (1) the mine waters may originate mainly from the Ordovician limestone groundwater inflows, and (2) the upward hydraulic gradient in the limestone aquifer may prevent its contamination by the overlying abandoned mine water. The results of this study could be useful for water resources management in this area and other similar mining areas.     

Weathering of the New Albany Shale, Kentucky, USA: I. Weathering zones defined by mineralogy and major-element composition

Comprehensive understanding of chemical and mineralogical changes induced by weathering is valuable information when considering the supply of nutrients and toxic elements from rocks. Here minerals that release and fix major elements during progressive weathering of a bed of Devonian New Albany Shale in eastern Kentucky are documented. Samples were collected from unweathered core (parent shale) and across an outcrop excavated into a hillside 40 year prior to sampling. Quantitative X-ray diffraction mineralogical data record progressive shale alteration across the outcrop. Mineral compositional changes reflect subtle alteration processes such as incongruent dissolution and cation exchange. Altered primary minerals include K-feldspars, plagioclase, calcite, pyrite, and chlorite. Secondary minerals include jarosite, gypsum, goethite, amorphous Fe(III) oxides and Fe(II)-Al sulfate salt (efflorescence). The mineralogy in weathered shale defines four weathered intervals on the outcrop—Zones A–C and soil. Alteration of the weakly weathered shale (Zone A) is attributed to the 40-a exposure of the shale. In this zone, pyrite oxidization produces acid that dissolves calcite and attacks chlorite, forming gypsum, jarosite, and minor efflorescent salt. The pre-excavation, active weathering front (Zone B) is where complete pyrite oxidation and alteration of feldspar and organic matter result in increased permeability. Acidic weathering solutions seep through the permeable shale and evaporate on the surface forming abundant efflorescent salt, jarosite and minor goethite. Intensely weathered shale (Zone C) is depleted in feldspars, chlorite, gypsum, jarosite and efflorescent salts, but has retained much of its primary quartz, illite and illite–smectite. Goethite and amorphous FE(III) oxides increase due to hydrolysis of jarosite. Enhanced permeability in this zone is due to a 14% loss of the original mass in parent shale. Denudation rates suggest that characteristics of Zone C were acquired over 1 Ma. Compositional differences between soil and Zone C are largely attributed to illuvial processes, formation of additional Fe(III) oxides and incorporation of modern organic matter.     

风化煤矸石抗剪强度粒径影响试验研究

煤矸石在排弃后粒径分布沿垂直剖面会呈现出明显的规律性,以现场煤矸石筛分级配为基础,进行了3试验级配下不同试样含水率时的风化煤矸石室内直剪试验。试验结果表明:低试样含水率时,风化煤矸石试验剪应力-剪位移曲线存在相对突出的峰值,呈明显应变软化现象;但随试样含水率的增加,风化煤矸石应力-应变关系呈现出明显的应变硬化特征。级配在不同含水条件下对风化矸石抗剪强度参数的影响存在差异,低试样含水率时粗颗粒形成的骨架对风化矸石内摩擦角有着重要影响,但随含水率增大,矸石细颗粒状态则对其起到控制性作用。各试验级配风化煤矸石内黏聚力随含水率增加差异减少试验值趋于一致,但内摩擦角的下降速率则明显存在区别,至饱和时风化煤矸石内摩擦角值下降至近零值,此时风化煤矸石试样抗剪强度主要由内黏聚力提供。     

Water quality impacts from mining in the Black Hills,South Dakota,USA

The focus of this research was to determine if abandoned mines constitute a major environmental hazard in the Black Hills. Many abandoned gold mines in the Black Hills contribute acid and heavy metals to streams. In some areas of sulfide mineralization local impacts are severe, but in most areas the impacts are small because most ore deposits consist of small quartz veins with few sulfides. Pegmatite mines appear to have negligible effects on water due to the insoluble nature of pegmatite minerals. Uranium mines in the southern Black Hills contribute some radioactivity to surface water, but the impact is limited because of the dry climate and lack of runoff in that area.     

废弃矿井地下水淹没过程的水流与水位数值模拟

定量分析和研究废弃矿井淹没过程的水流特征对于预测和防止废弃矿井地下水淹没过程中诱发的次生灾害具有重要意义。建立了废弃矿井淹没的多种介质水流数学模型,得出了淹没补给水量随时间、矿井内淹没水位和补给水源含水层水位之间的相关关系,建立了淹没补给水量与相关影响因素之间的函数关系式,完成了矿井淹没过程中涌水量实时计算的FEFLOW模块设计和开发。进行了近水平煤层开采后废弃矿井充水淹没水位回弹过程的数值模拟计算,得到了不同充水介质在充水淹没过程中的水流和水位回弹特征。结果显示,FEFLOW二次开发模块运算效果良好,具有实用价值。