Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

Current practice of underground artificial ground freezing(AGF)typically involves huge refrigeration systems of large economic and environmental costs.In this study,a novel AGF technique is proposed deploying available cold wind in cold regions.This is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling requirements.The introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration load.This design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the thermosyphon.Two Canadian mines are considered:the Cigar Lake Mine and the Giant Mine.The results show that our proposed design can speed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake Mine.Further,a cooling load of 2.4 GWh can be saved at the Cigar Lake Mine.Overall,this study provides mining practitioners with sustainable solutions of underground AGF.

Dust-Holding Capacity and Bio-Chemical Changes of Plant Species Growing in an Around Opencast Mining Area of Bundelkhand Region of Uttar Pradesh, India

The present study has been carried out on a total of 50 available plant species to assess their dust-capturing capacity and biochemical performances in and around open cast granite mine areas of Jhansi district and Bundelkhand University campus treated as control site. Plant species existing under a polluted environment for a long time may be considered as potentially resistant species and recommended for green belt design in mining areas, especially to cope with dust pollution. Results showed the pollution level, especially of mining-originated dust particles holding capacity of leaves and effects of different biochemical parameters (Total Chlorophyll, Protein and Carotenoid) of existing plant species both from mining areas as well as from Bundelkhand University campus. Based on their performances, Tectona grandis L., Ficus hispida L., Calotropis procera Aiton., Butea monosperma Lam. and Ficus benghalensis L., etc. are highly tolerant species while Ficus infectoria L., Artocarpus heterophyllus Lam., Ipomoea purpurea L., Allianthus excelsa Roxb. and Bauhinia variegata L. are intermediate tolerant species. T. grandis had shown the highest dust-holding capacity (2.566 ± 0.0004 mg/cm2) whereas Albizia procera (0.018 ± 0.0002 mg/cm2) was found to be the lowest dust-holding capacity. Our findings also showed that the T. grandis and F. hispida have significant dust deposition with minimal effect of dust on their leaf chlorophyll (17.447 ± 0.019 mg/g and 14.703 ± 0.201 mg/g), protein (0.699 ± 0.001 mg/g and 0.604 ± 0.002 mg/g) and carotenoid (0.372 ± 0.003 mg/g and 0.354 ± 0.003 mg/g) content respectively among all selected plant species. Therefore, in the present investigation, plant species with high tolerance to high dust-holding capacity on their leaf surfaces are preferable for green corridors as open cast granite mines and their adjacent areas.

A review on investigation of water-preserved coal mining in western China

Yushenfu mining area is located in an ecological fragile area in western China, the coal seam of which is the Jurassic Ysn'an Foirnalion. The Jurassic Yan'an Formation con tains five minable coal seams, the top layer of which is thick, covered by shallow overburden and located under aquifers. Therefore, the mining induced water flowing fractured zone can easily extend to the aquifers of both the Quaternary Sarahu and Jurassic Zhiluo Formation. This would result in a series of negative hydrological and ecological effects, including groundwater leakage, groundwater lowering, furtherly causing surface vegetation withering and dying, surface water body reduction, spring drying out, and water flow of river being decreased substantially. To solve these environmental problems, several technologies have been carried out by Chinese scientists, one of which is water-preserved coal mining. This paper presents a review of the origin, definition and development of water-preserved coal mining, and its applications in Yushenfu mining area. The applicable conditions, research contents, research methodology, and technical foundation of water-preserved coal mining are addressed in this paper. The future research focuses regarding water-preserved coal mining in China are also discussed in this paper. Its results serve as a guide for selecting the methods to be preferred for mining in case the geological conditions, roof overburden structure and coal mining process are similar to Yushenfu mining area.

Mechanical response of roof rock mass unloading during continuous mining process in underground mine

Taking the test stopes during continuous mining induced roof caving of Tongkeng ore-body No.92 as example, the calculation flow of unloading analysis was established. According to the unloading region division method of the affected zone theory, and the deterioration laws of mechanics parameters of unloading rock mass, the continuous mining process in underground mine was analyzed by the software MIDAS/GTS, the mechanical response of roof rock mass unloading was studied, and the differences were analyzed with the conventional simulation. The result shows that the maximum tensile stress, subsidence displacement and equivalent plastic strain of roof rock mass are 1.5 MPa, 20 cm and 1.5% in the unloading analysis, while 1.0 MPa, 13 cm and 0.9% in the conventional analysis. The values of unloading analysis, which are also closer to the actual situation, are greater than those of conventional analysis; the maximum step in continuous mining is 48 m, which shows that the induced treatment of the roof should be carried out after 2 mining steps

Surface movement and deformation characteristics due to high- intensive coal mining in the windy and sandy region

As China＇s energy strategy moving westward, the surface movement and deformation characteristics due to high-intensive coal mining in the windy and sandy region become a research hotspot. Surface movement observation stations were established to monitor movement and deformation in one super-large working face. Based on field measurements, the surface movement and deformation characteristics were obtained, including angle parameters, subsidence prediction parameters, etc. Besides, the angle and subsidence prediction parameters in similar mining areas are summarized; the mechanism of surface movement and deformation was analyzed with the combination of key stratum theory, mining and geological conditions. The research also indicates that compared with conventional working faces, uniform subsidence area of the subsidence trough in the windy and sandy region is larger, the trough margins are relative steep and deformation values present convergence at the margins, the extent of the trough shrink towards the goaf and the influence time of mining activities lasts shorter; the overlying rock movement and breaking characteristics presents regional particularity in the study area, while the single key stratum, thin bedrock and thick sand that can rapidly propagate movement and deformation are the deep factors, contributing to it.

Environmental Geochemistry of Mining Activities in Panzhihua Region, Southwestern China

Mining activities have created huge uncovered slopes, large areas of gangue ground and extensive tailings dams. This paper presents the environmental geochemistry of mining activities in Panzhihua region. The selected elements (Ti, V, Mo. Ni. Pb. Cu) show similar distribution patterns of concentration anomaly in topsoil. These concentration anomalies are located in V-Ti-magnetite slope, gangues dam and coal mine. The distinction between anthropogenic contamination and natural background is made available by the use of the enrichment factor in this study area. The anomalies of EF were smaller than that of concentration. The results from EF show that the selected elements anthropogenic pollution (EF>1) in topsoil were located in both the coal mining area and the V-Ti-magnetite mining area. In addition, the pollution sources of selected elements came from V-Ti-magnetite, slag, gangues, coal and other pollutants from mining activities.

Water protection in the western semiarid coal mining regions of China: A case study

The coal industry in China has been moving from the semiarid eastern to the drier western regions since the beginning of this century.Water protection is of the utmost concern for coal mining in these regions.Lu'an,as one of the state coal mining bases in China,has been seeing increasingly heavier pressure for the protection of water resources.This article considers Lu'an as an example and describes the ways these concerns may be alleviated.High mine-water utilization rates have effectively reduced wasting of water and,consequently,have reduced water demand.Using the top layers of the Ordavician as aquifuge barriers can prevent floor karst water inrush into the longwall face and can protect the regional Ordovician karst water resources at the same time.The strength of the overlying Quaternary clay can protect against roof collapse and has successfully preserved the Quaternary porous water resource.

Eco-geological environment quality assessment based on multi-source data of the mining city in red soil hilly region, China

High-intensity and large-scale resource development seriously threatens the fragile ecological environment in the red soil hilly region in southern China. This paper analyzes the eco-geological environmental problems and factors affecting Ganzhou, a mining city in the red soil hilly region,based on field survey and literature. The ecogeological environment quality(EGEQ) assessment system, which covered 11 indicators in physical geography, mining development, geological hazards,as well as water and soil pollution, was established through multi-source data utilization such as remote sensing images, DEM(Digital Elevation Model), field survey and on-site monitoring data. The comprehensive weight of each indicator was calculated through the Analytic Hierarchy Process(AHP) and entropy method. The eco-geological environment assessment map was developed by calculating the EGEQ value through the linear weighted method. The assessment results show that the EGEQ was classified into I-V grades from excellent to worse, among which, EGEQ of I-II accounted for 29.88%, EGEQ of III accounted for 32.35% and EGEQ of IV-V accounted for 37.77%;the overall EGEQ of Ganzhou was moderate. The assessment system utilized in this research provides scientific and accurate results, which in turn enable the proposal of some tangible protection suggestions.

Economic Characteristic of Coastal Community at Mining Region, Kotabaru Regency, Indonesia

Economic development of coastal community in Kotabaru Regency has become strategic in the future. Kotabaru Regency is the geo-economic strategic position due to the position of Kotabaru region boundaries between Kalimantan Island and Sulawesi Island. Geo-economic strategic of Kotabaru should increase the coastal community welfare in Kotabaru Regency. The objective of the research is to evaluate economic characteristic of coastal community at mining area in Kotabaru Regency. The number of samples in this study is 50 respondents in each village who are in the mining area. The number of companies in the mining area is 17 companies. Data were collected by using questionnaires. The results show that economic characteristics have low category. Mining and plantation companies do not increase the economic conditions of the community. Research suggestions are： （1） to examine the potential and importance of economic empowerment model of coastal communities in the region both mining companies and plantations; （2） the important role of companies and local governments to work together in formulating a strategy for management of CSR （corporate social responsibility）, and social mapping to be done by the company in the preparation of the CSR program.

Impact of Mining Activities upon Environment in Panzhihua Region, Southwestern China

Mining activities have left huge uncovered slopes, large areas of gangue ground and extensive railings dams. In this paper, we studied some impacts of mining activities upon environment in Panzhihua region, southwestern China. The environmental impacts include ecological destruction, geological disasters, environmental pollution, land damage, solid waste and occupational health effect in study area. The author suggested that local government should take some measure to reduce environmental impact in Pan...

Research on soil multi-media environmental pollution around a Pb-Zn mining and smelting plant in the karst area of Guangxi Zhuang Autonomous Region,Southwest China

The method of principal component analysis was applied to systematical research on the soil multi-media environment, including soil, surface water, ground water, waterbody sediment and agricultural crops, as well as pollution-inducing wastewater, mullock (or waste ore) and slag in the periphery of a large-sized Pb-Zn mining and smelting plant in a karst area of Guangxi Zhuang Autonomous Region. The results revealed that soils in the area studied have been heavily polluted by Cd, Zn, Pb and Hg, and the levels of these metals in the samples of agricultural crop greatly exceed the standards. The above-mentioned pollutants exist in all soil-multi-media environments. The mullock, slag, wastewater, surface water, ground water, soil, and agricultural crops constitute a composite ecological chain. Therefore, the improper disposal of mullock and slag, and the use of polluted wastewater for agricultural irrigation are the main causes of soil pollution. Heavy metals in the soil have three transition progresses: point (improved soil with slag, ground water inflow plot), linear (river transition) and non-point transition (regional pollution by slag) patterns, and the tailing yard is the most important locus for heavy metals to release into the environment.

LAND RECLAMATION IS BASIC GUARANTEE OF REGIONAL SUSTAINABLE DEVELOPMENT IN COAL MINING AREAS IN CHINA

Necessity of land reclamation is discussed, setting out viewpoint of sustainable development and land connotation and its attribute and combining destroyed forms and characteristics of land in coal mining areas. It is pointed out that land reclamation of coal mining areas is basic guarantee of solving contradiction between coal mining areas and countryside,raising life of resident and ensuring regional sustainable development.

Stability Assessment of Open Stope under Overlaying Mined-Out Regions at Modi Taung Gold Mine, Myanmar

Stability assessment is one of the most important issues in mining ground control. Mine development and/or production instability can cause production delay, loss of reserves, as well as injury to miners. Within the scope of this study, a series of open stope’s instability under the influence of overlaying mined-out regions were carried out with different mining scenarios at Modi Taung gold mine which is operated by National Prosperity Gold Production Group Limited (NPGPGL) in Myanmar. NPGPGL has been developing stopes up to 150 m from the surface at Shwesin vein system, and the mining activities are going to continue to deeper levels to fulfill the ore mineral supply. Creating a new stope opening under overlaying mined-out regions is not easy considering the instability of mined-out regions can affect the stope. The instability of new stope opening is not only due to its own induced stress but also the strong influence by the mined-out regions situated on upper part of the stope. Therefore, the understandings of ground behaviors and failure mechanisms of new stope opening due to the influence of overlaying mined-out regions are paramount to be studied. This paper describes in detail the strength factor and failure zones under the overlaying mined-out regions with different mine conditions by using numerical simulations, 3D finite difference software (FLAC 3D).

Environmental complaint insights through text mining based on the driver,pressure,state,impact,and response(DPSIR)framework:Evidence from an Italian environmental agency

Individuals,local communities,environmental associations,private organizations,and public representatives and bodies may all be aggrieved by environmental problems concerning poor air quality,illegal waste disposal,water contamination,and general pollution.Environmental complaints represent the expressions of dissatisfaction with these issues.As the timeconsuming of managing a large number of complaints,text mining may be useful for automatically extracting information on stakeholder priorities and concerns.The paper used text mining and semantic network analysis to crawl relevant keywords about environmental complaints from two online complaint submission systems:online claim submission system of Regional Agency for Prevention,Environment and Energy(Arpae)(“Contact Arpae”);and Arpae's internal platform for environmental pollution(“Environmental incident reporting portal”)in the Emilia-Romagna Region,Italy.We evaluated the total of 2477 records and classified this information based on the claim topic(air pollution,water pollution,noise pollution,waste,odor,soil,weather-climate,sea-coast,and electromagnetic radiation)and geographical distribution.Then,this paper used natural language processing to extract keywords from the dataset,and classified keywords ranking higher in Term Frequency-Inverse Document Frequency(TF-IDF)based on the driver,pressure,state,impact,and response(DPSIR)framework.This study provided a systemic approach to understanding the interaction between people and environment in different geographical contexts and builds sustainable and healthy communities.The results showed that most complaints are from the public and associated with air pollution and odor.Factories(particularly foundries and ceramic industries)and farms are identified as the drivers of environmental issues.Citizen believed that environmental issues mainly affect human well-being.Moreover,the keywords of“odor”,“report”,“request”,“presence”,“municipality”,and“hours”were the most influential and meaningful concepts,as demonstrated by their high degree and betweenness centrality values.Keywords connecting odor(classified as impacts)and air pollution(classified as state)were the most important(such as“odor-burnt plastic”and“odor-acrid”).Complainants perceived odor annoyance as a primary environmental concern,possibly related to two main drivers:“odor-factory”and“odorsfarms”.The proposed approach has several theoretical and practical implications:text mining may quickly and efficiently address citizen needs,providing the basis toward automating(even partially)the complaint process;and the DPSIR framework might support the planning and organization of information and the identification of stakeholder concerns and priorities,as well as metrics and indicators for their assessment.Therefore,integration of the DPSIR framework with the text mining of environmental complaints might generate a comprehensive environmental knowledge base as a prerequisite for a wider exploitation of analysis to support decision-making processes and environmental management activities.

缅甸地质矿产特征与矿业投资环境分析

缅甸位于中国西南和印度洋之间,是“一带一路”中缅经济走廊的重要节点,也是中国西南通向印度洋、连接东南亚的便捷通道。缅甸固体矿产资源较为丰富,但地质工作研究程度较低,因而具有良好的矿业投资前景,尤其是近年来缅甸政府陆续更新了矿业政策,对外国赴缅矿业投资的限制进行了优化,以此吸引更多的投资者在缅进行矿业勘查开发,振兴缅甸矿业经济。文中介绍了缅甸地质与矿产资源概况、近十年勘查开发形势及主要矿山开发现状,重点解读了近年来缅甸政府颁发的新的《矿业法》和《矿业法实施细则》等文件,以期更加深入地理解缅甸矿业政策的新变化、新动向和新趋势,为中资企业开展缅甸矿业投资开发提供依据。同时,提出相关的建议,包括需要及时跟进矿业市场动态、了解在缅项目负面清单、科学把握政策要点、提前研判与缅甸政府合作的优劣模式以及履行企业社会责任等。笔者分析缅甸资源禀赋和矿业开发现状、深入解读缅甸新颁布的矿业法和矿业政策,对企业在缅甸矿产勘查和矿业投资合作具有一定指导意义。

煤层底板含水层区域注浆改造浆液扩散范围现场示踪试验

近年来,为解放底板高承压灰岩水上煤炭资源,华北煤田普遍采用地面定向钻技术,对太原组薄层灰岩进行区域性注浆加固改造(习称“底板区域治理”),以全面封堵灰岩岩溶裂隙并阻断垂向导水通道。该技术中,与浆液扩散范围(半径)密切相关的“水平分支孔”孔间距设计问题,一直备受学界和业界的广泛关注。皖北矿区底板区域注浆工程量大,特别是深部资源开采,将有数十亿元的注浆工程,有必要查清浆液扩散范围真实数据。为此,以皖北矿区恒源煤矿为研究基地,依托Ⅱ63采区底板区域治理工程,设计并实施浆液扩散范围示踪试验,在中间的水平分支孔(Z8-7)投放荧光剂(示踪剂),在两侧的水平分支孔(Z8-6、Z8-8)以及交叉分支检测孔(Z8JC)取岩屑样鉴别荧光水泥,以获得浆液扩散范围,进而在浆液扩散影响因素分析基础上,构建恒源煤矿底板区域注浆治理浆液扩散范围计算公式。结果表明:①综合岩屑现场及室内鉴别结果分析,获得恒源煤矿Ⅱ63采区底板区域注浆浆液扩散范围为38.3~44.0 m,且水泥分布密集区在水平分支孔浆液扩散范围30 m以内,该区域内注浆效果最佳。②通过现场岩屑快速鉴别与室内岩屑精准鉴别,取得的浆液扩散范围基本一致,证明了荧光示踪浆液扩散范围的有效性。③通过对比分析,认为在计算参数、边界约束等符合实际注浆工况条件下,浆液扩散范围理论计算和数值模拟结果,与现场示踪试验实测结果较为接近。④利用示踪试验过程中的压水试验及注浆参数、钻遇构造及水文地质响应等数据,考虑重力、构造、地下水径流等因素影响,借助SPSS非线性拟合软件,得到恒源煤矿Ⅱ63采区底板区域注浆浆液扩散范围计算公式。⑤基于恒源煤矿受注层实际地质、水文地质条件,利用拟合的浆液扩散范围计算公式得出Ⅱ63采区Z8场地浆液扩散范围为37.8~42.9 m,与浆液扩散范围示踪试验实测结果相近,计算公式可在类似条件下推广应用。本次煤矿底板区域注浆浆液扩散范围现场示踪工程试验,不仅取得了浆液扩散范围的真实数据,而且阐明了浆液扩散与多种地质、水文地质因素之间的内在联系,揭示了超深、超长定向钻注浆浆液扩散机理,构建了浆液扩散范围计算公式,为类似条件下底板区域治理工程水平分支孔孔间距的合理设计提供了参考依据。

灵泉露天矿生态修复效果及驱动因素分析

煤矿开采通常会破坏土壤、植被,从而造成生态损伤。目前,高寒地区露天矿的生态修复工作尚处在起步阶段,针对高寒地区露天矿开展的生态修复效果及其驱动因素分析的研究较少。以灵泉露天矿为研究区,基于2009—2022年共11期Landsat影像,利用像元二分模型计算植被覆盖度,对矿区生态修复前后开展长时序植被覆盖动态监测,并进行生态修复效果和驱动因素分析。研究结果显示:矿区近十年来的植被覆盖度总体呈上升趋势,2017年大面积修复以后上升趋势尤为显著。气温和降水量是导致高寒地区露天矿植被覆盖度发生波动性变化的关键自然因素,其中,降水量是影响植被覆盖度持续上升的主要自然因素。植被覆盖度和土壤养分含量的变化相辅相成,植被覆盖度上升的同时会使土壤肥力提升,土壤肥力提升后又会促进植被覆盖度的上升。人工修复是高寒地区露天矿生态修复的主要方式,是高寒地区露天矿植被覆盖度上升的主要原因。研究结果表明,多年来的生态修复工作取得了显著效果,同时可为高寒地区露天矿的生态修复提供科学依据。

基于Kaiser效应的地应力差应变测试及区域地应力分布研究

以往差应变分析法(DSA)通过估算垂向主应力以求解地应力,使得该方法可靠性较差。基于岩石试样的Kaiser效应,结合差应变法,提出了一种基于Kaiser效应的地应力差应变测试方法(Kaiser-DSA法),并利用Kaiser-DSA法与应力解除法进行了对比,表明Kaiser-DSA法测试结果与应力解除法的测试结果相对误差小,且最大水平主应力方向基本一致;基于地应力测试结果,分析了窑街矿区地应力分布规律,探究了窑街矿区现今地应力场成因。结果表明:窑街矿区区域上受到了挤压构造应力场的作用,残余应力较高;受青藏逆冲推覆作用与F19断层的顺时针剪切作用,该区域地应力场以σH(最大水平主应力)>σv(垂向主应力)>σh(最小水平主应力)型的走滑型应力状态为主;此外,较高的差应力使得该区域回采时围岩体变形破坏严重,动力灾害事件频发。

监测数据驱动的寒区混凝土坝温度特征分析

鉴于寒区混凝土坝的服役环境具有的冬季气温极低、温差悬殊、寒潮频发和冻融循环剧烈等特点对大坝安全带来的不利影响,针对寒区混凝土坝环境温度和坝体温度监测数据,通过构造反映温度增量距离和温度变幅距离的综合相似性距离指标,应用层次凝聚聚类算法,提出了辨识寒区环境气温地域特征的数据聚类挖掘方法;并针对常规坝体温度场变化表征模型的不适用性,构建了融合谐波因子、气温前期项和水温前期项的寒区混凝土坝坝体温度场表征模型,提升了温度场刻画精度,为实现分析寒区混凝土坝温度场和演变规律,动态跟踪大坝安全状态提供了理论和技术支持。

基于时空连续补偿的矿山可通行区域识别方法

可通行区域识别是矿山无人驾驶技术中的重要环节。露天矿山道路场景具有道路边界模糊不清及路面平坦度不一等特征,使用传统同心圆地面分割模型进行矿山道路平面拟合时容易出现可通行区域与车辆不连通及帧间可通行区域识别结果不一致等误分类问题。提出了一种基于时空连续补偿的矿山道路可通行区域识别方法。首先,基于同心圆模型对矿山道路建模,并利用主成分分析方法进行多平面拟合,获取初始可通行区域分割结果;然后,基于空间连通性,分别利用区域生长方法和基于密度的噪声应用空间聚类方法对初始可通行区域进行区域连通性滤波及点连通性滤波,得到符合空间连通性的可通行区域;最后,基于时间区域一致性对不同点云帧中可通行性不一致的不稳定区域进行滤除,先根据正态分布变换方法构建栅格地图,再利用时间稳定权重判断栅格稳定性,最终通过区域栅格投影实现不稳定区域的滤除。矿山场景中测试结果表明:该方法的准确率为93.44%,较现有主流方法提升2.27%;召回率为99.14%,较现有主流方法提升8.26%。该方法不仅在不连通区域中具有良好的空间连通性,还在崎岖区域内具有良好的时序稳定性。