Mine water pollution in Scotland: nature, extent and preventative strategies

Scotland was one of the world's first industrialised countries, and has therefore also been one of the first countries to experience wholesale post-industrial dereliction. Water pollution arising from abandoned mines, particularly abandoned coal mines, is second only to sewage as a source of freshwater pollution nation-wide, and in many coalfield catchments it is the pre-eminent source. Most of the pollution is due to net-alkaline ferruginous waters emerging from deep mines. Scrutiny of records from 80 deep mine discharges reveals that iron concentrations in these waters are only likely to exceed 20 mg/l, and the pH to be below 6.5, where the discharge emerges within 0.5 km of the outcrop of the shallowest mined seam. The bulk of mature near-outcrop mine water discharges in Scotland have < 50 mg/l total Fe, and concentrations > 100 mg/l are only likely where a marine bed lies within 25 m of the worked seam. Where the nearest marine bed is more than 80 m above or below the seam, then the total iron will be less than 4 mg/l, and in most cases less than 1 mg/l. Net-acidic mine waters are far more rare than net-alkaline waters in Scotland, and are most commonly associated with unreclaimed spoil heaps (bings). Both net-alkaline and net-acidic discharges have detrimental effects on the hydrochemistry and biological integrity of receiving waters. Scotland has recently pioneered the use of pre-emptive pump-and-treat solutions to prevent mine water pollution, and has also experienced the successful introduction of passive treatment technology for both abandoned and active workings.     

The influence of an abandoned goaf on surface subsidence in an adjacent working coal face: a prediction method

Historical global coal resource exploitation has resulted in goaf abandonment at most mines, which, during the life of the mine, exerts a strong influence on the ability to exploit new working faces adjacent to any abandoned goaf. Thus, the distribution law of the surface subsidence basin above the new working face differs from the general law. Given the lack of research on this distribution law, this study uses a similar material simulation method to examine the influencing mechanism(s) of abandoned goafs on the subsidence basin in the same coal seam. Synthetic aperture radar (SAR) monitoring results of the 9310 working face in the Nan Tun coal mine, Yanzhou, China, are used to verify analytical results, followed by numerical simulation to study the influence of the abandoned goaf on the subsidence basin. Finally, to accurately predict surface subsidence influenced by the abandoned goaf, inflection point deviations are selected and discussed in terms of the probability integral method. This allows for prediction of the distribution of the surface subsidence basin, and moreover, the predicted results are found to be consistent with the SAR monitoring results when the derivation of inflection points is revised.     

Highway construction across heavily mined ground and steep topography in southern China

Due to rapid expansion of the highway network in southern China in recent years, abandoned mine areas have been increasingly considered for highway construction. It is particularly challenging to carry out the assessment and remediation of mining subsidence effects on highway infrastructures, including high-filling embankments, deep-cutting slopes, and bridges. This article describes the subsidence mechanisms of abandoned mines with longwall workings and room-and-pillar systems, and also the potential geohazards and risks associated with abandoned mines. A hazard zonation criterion adopted for highway design and construction in China is introduced, as well as the possible remedial measures that can be carried out for various highway infrastructures. In the case study, grouting was used to fill cavities and stabilize the voids, and a two-layered geogrid was incorporated in the sub-base and embankment to avoid subsidence or sudden collapse of the ground. The remedial measures applied to deep-cutting slopes involved grouting, an anchor, or grid beam, employed either alone or in combination. In addition, a reinforced soil-piled embankment was utilized to reduce differential settlement at the transition zone between a bridge abutment and embankment. Based on the experiences gained, recommendations for future projects are given.     

废弃矿山地下空间开发利用典型模式探究

废弃矿山即矿业废弃地,也是一种占用土地资源和对环境、经济、社会有潜在利用价值的棕地。目前国内外学者大多关注露天矿,忽略了矿山地下空间的开发利用。然而,废弃矿山地下空间是宝贵的人造空间,应当打破传统的开发模式,重新激活生命周期。因此,笔者梳理了我国废弃矿山地下空间开发的现状,以欧洲代表国家捷克为例,根据该国石灰石矿-Amerika采石场群、铁矿-Skalka博物馆、金矿-Josef地下廊道、铀矿-Bukov地下廊道4个案例,分析了可借鉴的经验教训和较好的应用前景,总结出两类4种主要开发模式,结合我国开发现状展开深入讨论,为我国废弃矿山地下空间开发与利用提供经验范式。     

Socio‐economic impacts of mine closure: a case study using satellite imagery

Mine closure normally leaves an adverse impact on the environment and society that, if left unattended, may last for years to come. In India the Raniganj Coalfields of Coal India Limited may be facing severe social and ground stability problems as a result of numerous old, abandoned mines. Already subsidence has occurred in a number of places, such as the Salanpur, Baraboni and Jamuria areas of the Raniganj coal fields. The study presented here highlights the socio‐economic problems faced by the area. Using remote sensing techniques the authors have assessed the socio‐economic factors of the area and they recommend various remedial measures to overcome the adverse impacts of mine closure.     

废弃矿山水生态的弹性塑造——邯郸市 紫山公园设计实践

以邯郸市紫山公园设计为例,围绕海绵城市与废地矿山的相关理论,对废弃矿山水生态的弹性塑造进行深入探讨,详细研究废弃矿山景观规划设计的4个方面:地形——人工海绵框架的构建;水体——水生态网络的重构;植被——生命景观的提出;生境——时间与事件的引入。通过研究来阐述和总结水生态设计的策略,以期对当下及未来废弃矿山的景观再造提供有益的参考。     

Assessment of rock mass characteristics and the excavation disturbed zone in the Lingxin Coal Mine beneath the Xitian river, China

Safe production and induced hazard prevention in coal mines mainly concern problems in the excavation disturbed zone (EDZ), but coal mining can also make a significant impact on the environment. Comprehensive techniques using a borehole TV viewer system, electrical logging, and monitoring of drilling fluid leakage offer the ability to identify changing geological conditions and the location of any nearby abandoned mining workings. The inner collapsed zone and the expanding height of the crack zone transmitting water plus their spatial distribution after excavating the superincumbent coal seam stratum are determined at no. L3414 workings, Lingxin Coal Mine beneath the Xitian river, China. An integrated system of GIS-based on a stochastic model, which has been developed for the prediction of dynamic subsidence coupling the time function and probabilistic integral method, is verified through practice at the Lingxin Coal Mine. This development has greatly expanded the ability of the mine operator to characterize previously inaccessible areas of the mine, providing a reliable basis for safe mining and prevention of induced-hazards to ensure high production mining underneath the river bed.     

Long-term changes in quality of discharge water from abandoned underground coal mines in Uniontown Syncline, Fayette County, PA, USA

Changes in water quality over 25 years have been documented for discharges from an extensive network of abandoned underground coal mines in the Uniontown Syncline, Fayette County, PA, USA. A baseline study of 136 mine discharges in the syncline was conducted in 1974-1975. In 1998-2000, follow-up water flow and quality monitoring was conducted at 21 selected discharges for 2 years to assess the degree of mine water-quality improvement since 1974-1975. The data from the two periods of time were compared, with consideration of differences in measurement methods. The degree and rate of water-quality improvement was found to be highly dependent on the amount and duration of flooding in the mine voids. Water quality of discharges from the substantially flooded mine voids improved significantly, going from acidic water with high sulfate and iron concentrations in 1974-1975 to alkaline water with substantially lower sulfate and iron concentrations in 1998-2000. In contrast, the water quality in the unflooded mines showed less improvement over the 25 years between studies. The water discharging from the unflooded mines in 1974-1975 was acidic with high sulfate concentrations and in 1998-2000 was still acidic but showed somewhat lower sulfate and iron concentrations, reflecting depletion of readily available pyrite. The data obtained provide insight into the potential and rate of natural amelioration of mine water quality in different abandoned underground coal mine systems.     

盐矿水溶开采地表塌陷发生机理及防治措施

水溶开采诱发地表塌陷是盐矿开采中常见的地质灾害现象,具有突发性强、破坏程度大、持续时间长等特点。系统分析了近几十年来盐矿地表塌陷的典型实例,指出溶腔不稳定造成的垮塌、卤水及地下水侵蚀诱发断层活化以及上覆岩土体侵蚀破坏后承载力降低是水溶开采诱发采区地表塌陷主要的三种模式,并揭示了塌陷发展过程中各个因素的相互作用和影响。为防止盐矿塌陷的发生,分别从理论与试验研究、地质勘查、矿井设计以及生产管理等方面提出了相关的建议和措施。     

Inventory of aquatic contaminant flux arising from historical metal mining in England and Wales

The impact of discharges from abandoned metal and ironstone mines has been a much studied form of aquatic pollution in recent decades. Few attempts however, have been made to accurately determine the overall contaminant mass flux arising from abandoned mine sites at scales above catchment level. Such assessments are critical to determine the significance of former mining to national, regional and ultimately global trace metal flux. This paper presents the most comprehensive national survey to date across England and Wales of the total pollution burden discharged at source from abandoned non-coal mine sites. 338 discharges have been identified (from 4923 known abandoned metal mines) and while concurrent flow and contaminant concentration records are only available for around 30% of these, significant quantities of metals (and As) have been quantified to be discharged. A minimum of 193 tonnes of Zn, 18.5 tonnes of Pb, 0.64 tonnes Cd, 19.1 tonnes of Cu, 551 tonnes Fe, 72 tonnes Mn and 5.1 tonnes As are released in water discharges from abandoned non-coal mines to the surface water environment of England and Wales each year. Precautionary extrapolation of mass fluxes based on the frequency distribution of measured concentration and flow data, for discharges with absent data, suggests that the actual total mass flux for these contaminants could be up to 41% higher. The mass flux of Pb released from mines exceeds that of all currently permitted discharges (e.g. active industrial sites and wastewater treatment works) to surface waters across England and Wales, while those of As, Cd and Zn are of a similar magnitude. These data put into context the enduring legacy of historic mining on the water environment, highlighting its significance relative to more highly regulated polluting sites. Comparison of the figures with estimates of global trace metal flux suggests that the national total identified here is significant on a global scale.     

Possible Environmental Impact of the Closure of Two Collieries in County Durham

In County Durham the forthcoming closure of two coastal collieries is, in effect, the final closure of a large hydraulically interconnected coalfield which has been progressively dewatered over three centuries. Groundwater will gradually rise through the previously worked strata after the cessation of coalfield dewatering. Past experience shows that the rising groundwater will develop high acidity and heavy metal loadings as oxidized pyrite remnants are dissolved. Conceptual modelling suggests that this acidic groundwater will ultimately discharge into the River Wear and its tributaries, with serious consequences for the aquatic ecology and human use of the River Wear system. Further environmental impacts may include (a) groundwater pollution in the adjacent Basal Permian Sands aquifer, (b) leaching from landfills intersected by the rising water table, (c) compromised integrity of foundations, (d) increased flows in old sewers below the new rest water level (leading to problems at sewagetreatment works and combined sewer overflows), (e) corrosion of other buried services, (f) surface gas emissions, and (g) long-term subsidence risk from old workings. The prevention of these impacts would involve long-term maintenance of regional dewatering, although local mitigation of most effects could be arranged – albeit at considerable cost. Current legislation fails to place responsibility for the prevention of such environmental impacts in the hands of any one organization; this 'vacuum of responsibility'needs to be addressed urgently if a pragmatic, consensual approach to environmental protection in abandoned coalfields is to be pursued.     

Modelling of the drying and flooding of underground iron mines in Lorraine (France)

Mining collapses currently occur in Lorraine (France) above abandoned room-and-pillar iron mines during the transient stage of mine flooding. The mining rocks are exposed in situ to various hydrous conditions: full saturation–partial saturation (ventilation)–full saturation. In order to explain the mechanisms involved in mining collapses, we have performed one- and two-dimensional numerical simulations based on a poroplastic model and within the framework of partially saturated and continuous porous media. These numerical simulations model the hydrous cycle imposed to the rocks in these underground deep mines. It results from this hydromechanical modelling that the final stage of resaturation induces transient tensile stresses that lead to failures at the roof and at the floor of the galleries. These instabilities appear during the transient stage of resaturation only if the variation of the equivalent interstitial pressure π is important. The studied key points are the complex geometry of the model (rectangular rooms and dissymmetry of the upper and lower boundaries conditions) and the kinetics of the fluids diffusion processes that makes the reversibility very long and induces an important hysteresis in the hydromechanical cycle. The convergence measurements in an in situ experimental site, in which the flooding of the mine has been simulated, are well modelled.     

废弃矿山生态修复治理技术应用——以北京房山区废弃矿山为例

近年来北京周边大气污染问题日趋严重,北京市远郊区县留存各类废弃矿山,矿山地质环境问题日益突出。文章研究废弃矿山的生态修复,主要针对北京市房山区存在的石材矿与煤矿地质环境、地形、土壤等各项环境特点,对地形整治、植被修复的模式、方法进行探讨。     

Mercury and methylmercury concentrations and loads in the Cache Creek watershed, California

Concentrations and loads of total mercury and methylmercury were measured in streams draining abandoned mercury mines and in the proximity of geothermal discharge in the Cache Creek watershed of California during a 17-month period from January 2000 through May 2001. Rainfall and runoff were lower than long-term averages during the study period. The greatest loading of mercury and methylmercury from upstream sources to downstream receiving waters, such as San Francisco Bay, generally occurred during or after winter rainfall events. During the study period, loads of mercury and methylmercury from geothermal sources tended to be greater than those from abandoned mining areas, a pattern attributable to the lack of large precipitation events capable of mobilizing significant amounts of either mercury-laden sediment or dissolved mercury and methylmercury from mine waste. Streambed sediments of Cache Creek are a significant source of mercury and methylmercury to downstream receiving bodies of water. Much of the mercury in these sediments is the result of deposition over the last 100-150 years by either storm-water runoff, from abandoned mines, or continuous discharges from geothermal areas. Several geochemical constituents were useful as natural tracers for mining and geothermal areas, including the aqueous concentrations of boron, chloride, lithium and sulfate, and the stable isotopes of hydrogen and oxygen in water. Stable isotopes of water in areas draining geothermal discharges showed a distinct trend toward enrichment of (18)O compared with meteoric waters, whereas much of the runoff from abandoned mines indicated a stable isotopic pattern more consistent with local meteoric water.     

资源城市井露采动引起公路沉陷灾害机理研究

针对资源城市矿产开采规模的扩大和交通货物运输量的日益增长,使得井工、露天矿区基础运输设施建设以及与之紧邻的城市交通建设和开采引起的公路沉陷灾害的矛盾越来越突出。本文针对资源城市—山西溯州市平溯矿区井露联合开采新模式引起的矿区公路与地面建(构)筑物变形与破坏这一情况,利用模拟分析技术进行了开采对公路造成沉陷机理和演化规律的研究,并建议了相应的处治措施。     

深部开采条件下矿区城市地基建设的数值模拟分析

应用矿山灾害力学及结构力学等相关理论,针对我国各矿区正转入深部开采的现实情况,对矿区城市中的楼体地基建设的稳定性进行了数值模拟研究,得到了不同采深、不同高度楼房建设条件下地基及地下岩体的应力、变形及沉降规律,并借助相似材料模拟实验进行验证。结果表明:深部开采条件下,矿区城市地基所受应力主要体现在底部连接处,地基中部发生的变形和沉降较大。开采深度越大地基所受影响反而较小,楼层越高地基变形越大。通过相似材料模拟实验分析实际采区开采后的地表变化,发现开采深度较浅情况下地表破坏明显严重,而深部开采时地表所受破坏情况较小,但当地表承重加强时会发生破坏。模拟和实验为矿区城市在深部开采条件下的地基建设提供参考。     

Attenuation of mining-derived pollutants in the hyporheic zone: a review

Mine water pollution is a major cause of surface- and groundwater pollution in former mining districts throughout Europe. It is a potential barrier to achieving good status water bodies, which is a requirement of the EU Water Framework Directive. In the UK, a concerted effort has been made over the last decade or so to address the scientific and practical challenges relating to the remediation of mine water pollution. However, most of this work has focused on remediation of point sources of pollution (typically arising from abandoned mines and shafts), while the behaviour of mine water at the groundwater-surface water interface (the "hyporheic zone") has received far less attention in relevant scientific and engineering literature. The extent of mine water pollution and capacity for its attenuation at the hyporheic zone has not been well quantified while, furthermore, the complex chemical and microbial processes occurring there (specifically with reference to mining-derived pollutants) have not been investigated in any depth. The absence of such data may relate, in a large part, to the difficulty in physically measuring volumes and concentrations associated with these river inputs/exports. A far greater body of literature addresses biogeochemical processes at the hyporheic zone (especially relating to manganese), albeit many such articles relate to aqueous metal dynamics in general, rather than mine water specifically. This paper presents a review of the natural attenuation processes that may limit the movement and availability of mining-derived pollutants at the groundwater-surface water (GW-SW) interface, and specifically within the hyporheic zone. A substantial part focuses on precipitation and adsorption processes at the hyporheic zone, as well as discussing the role of microbial processes in governing metal ion mobility.     

Influence of the stress state in a coal bump-prone deep coalbed: A case study

The effect of stress is one of the main natural factors that exerts a significant influence in coal bumps and rock bursts, especially in deep coalbeds. Sublevel caving is one of the methods that most influences this stress state and is therefore an extremely important parameter to consider when trying to improve mining conditions in mines with high methane content. This paper presents a practical case to illustrate the stress behavior of sub-vertical coalbeds in deep mines. The site study included two different locations, in two mines in the Riosa-Olloniego coalfield (Asturias, Spain) that are presently being mined by the sublevel caving method at a depth of around 1000 m. The research analyzed the influence that the caving of a particular panel of coal has on the upper and lower sublevels of the coalbed itself, as well as of neighboring coalbeds, with the aim of comparing different mining sequences. The site measurements carried out had two aims: to test the influence of adjacent workings on the 8th Coalbed and its coal-bearing strata and to verify the influence of the stress–strain change on the occurrence of coal bumps. Besides fulfilling these objectives, the work has also provided data for the calibration of possible numerical models that allow the simulation of present and future situations in the mine and has contributed to improving safety conditions of mining works in coal bump-prone deep coalbeds.     

Some examples of the impact of metalliferous mining on the environment: a South African perspective

Metalliferous deposits have played and continue to play a vital role in the economy of South Africa, gold being the most important. The shallow early mines, now abandoned, give rise to subsidence. As a result, the erection of buildings on the undermined land in the old reef area, which runs east to west through the city of Johannesburg, has been controlled by the Government Mining Engineer, including the permissible heights of buildings in relation to the depth of the mining. More recently, the controls have been relaxed when development proposals have been accompanied by sound methods of mine stabilization. Various types of subsidence are discussed, including both the development of sinkholes, which can take place rapidly and have catastrophic results and loss of life, and dolines, associated with dewatering activity. Induced seismicity has also been associated with gold mining. Investigations showed that the seismic events originated near working faces and occurred around the time of blasting. With magnitudes rarely exceeding 3, rarely is there significant surface damage. The conditions in which acid mine drainage related to the oxidation of sulphide minerals develops and the associated problems are also discussed. Case histories are presented to illustrate the environmental problems related directly and indirectly to the mining. Electronic Publication     

程潮铁矿西区地下开采引起的地表变形规律初探

 以湖北鄂州程潮铁矿西区为例,依据近6 a的地表水平位移、沉降位移变形监测成果,对地下开采引起的地表变形规律进行分析。结果表明：程潮铁矿西区从地表塌陷至今,等值线、移动线和陷落线在矿区东北端扩展最多,并且在2010年1月,设置的关卡门至措施井往西约150 m的矿区公路(以下简称矿区公路)、粉矿堆场及运输隧道东南端处的地表岩体突然加速,究其原因是矿区水平应力得到较大程度的释放,特别是东北端,使得矿区公路和粉矿堆场处深部岩体开始形成弯曲折断面,目前进入沿着高陡倾角的拉张裂缝向采空区的倾倒滑移破坏阶段,地表岩体以快速变形为主,而运输隧道东南端处的深部岩体只是发生弯曲变形,地表岩体在经历较短时间的快速变形之后,又线性稳定增长,进入倾倒破坏阶段。其成果能为其他类似的金属矿山工程提供可借鉴的规律。