武汉地区工程中的地下水问题及其处理对策

本文介绍了武汉地区的水文地质概况 ,基坑工程中的地下水问题及其处理对策。重点讨论了管井降水、隔渗和降水与隔渗的配合使用。对地下水处理过程中的环境保护问题进行了详细的讨论。     

POTENTIAL GROUNDWATER IMPACTS FROM CIVIL-ENGINEERING WORKS

Civil-engineering construction works often have a significant impact on groundwater conditions. Such an impact can range from the derogation of water sources by dewatering works, to the creation of barriers and pathways for groundwater flow formed by foundations or ground-improvement processes. In some cases, not all these impacts are identified early enough during the planning and design process.
This paper describes the full range of potential groundwater impacts which can result from construction activities. The effects are grouped into five rational categories as an aid to initial assessment. The need for accurate baseline groundwater environmental data is set out. and recommendations are made for the planning of monitoring programmes.     

艾娜克铜矿水源地地下水允许开采量计算及影响评价

为保护阿富汗艾娜克铜矿一带地下水资源环境,同时在开采期间不发生危害性的环境水文地质问题,根据在阿富汗艾娜克铜矿一带进行的供水水文地质勘查成果及水源地稳定流抽水试验成果采用补偿疏干法对水源地的允许开采量进行计算并对水源地取水后对当地地质环境的影响程度进行评价,本水源地为山间河谷调节型水源地,本次研究确定的地下水资源储量1 255~28 m3/d,精度为探明的(B级)允许开采量。水源地开采运行后不会对周边产生危害性沉降,但是会对影响半径范围内的(北段1 240 m、南段1 860 m)居民生活生产用水造成不同程度的影响,需要采取相应的措施确保铜矿水源地正常开采运行。     

Groundwater Rebound in the Leicestershire Coalfield

The Leicestershire coalfield has been mined for at least eight hundred years, the last deep mine closing in 1991. The earliest shallow mines on the exposed coalfield are not recorded on plan, but were later connected to the deeper workings in many seams. In order to protect the last deep mines, pumping was maintained from the abandoned mines to the north.
Water-table rebound was observed prior to closure, and is now affecting the surface. Increased emissions of poor-quality water into low-discharge surface water-courses are predicted. Renewed subsidence has implications for roads, services and property. Rising water levels will affect old opencast excavations and waste disposal sites.
Fieldwork and abandoned mine plan inspections have demonstrated renewed subsidence and evidence of increased emissions in those low-lying areas of the exposed coalfield which are believed to be most at risk.     

Environmental effects under China’s Western Development Strategy: a case study in the Beipan River basin,Guizhou

This paper is based on a case study in the Beipan River basin, which aims to assess the success of environmental initiatives in southwest China under the national Western Development Strategy. The research uses data searching, interviews and in situ observation. The results of erosion, Karst stony-desertification, reforestation and the water quality of the Beipan River reveal that the ecosystems in the basin were improved during 2000–2012. Geology, topography, hydrology, climate and human impacts will remain major challenges to the future ecological conservation and environmental protection. Future environmental development in the basin and southwest China will demand a long-term, holistic approach to overcome both natural and human impacts.     

地下水位变化对邻近地铁结构的影响研究

为了研究地下水位变化对邻近地铁结构的影响,以天津某基坑为研究对象,通过统计基坑施工过程中地下水位的变化,进一步研究基坑周边地下水位的变化及邻近地铁结构的变形.结果表明基坑施工过程中降水会影响周边地下水位的变化,进而会导致邻近地下构筑物的变形,其中承压水对周边环境的影响尤其显著;今后基坑施工过程中的降水一定要注重对周边环...     

Conservation concept for a river ecosystem (River Spree, Germany) impacted by flow abstraction in a large post-mining area

In the Lusatia region of northeastern Germany, dewatering for mining activities has resulted in an 8-km³ deficit in the groundwater balance. In order to refill aquifers and empty lignite pits, water will be abstracted for several decades from the River Spree which drains this region. This affects the ecological integrity of a 230 km river section including the floodplain in several aspects. Ecological consequences are shown for fishes, the aquatic invertebrate fauna, the retention of suspended matter, and oxygen concentrations. Therefore, an ecologically based minimum discharge has to be instituted. Current concepts on the assessment of minimum flow requirements in streams are reviewed. A multiple compartment method (MCM) for the assessment of flow requirements in extended river sections is suggested. Using the MCM, it can be shown that the minimum discharge that is required to preserve the river ecosystem is largely influenced by ambient channel morphology and nutrient concentration. This means that the ecological impacts of water abstraction could be abated by measures of morphological restoration of the river as well as of nutrient input restriction. Also, instream minimum flow requirements would be reduced, so that more river water could be abstracted, and the restoration of the water balance in the post-mining area in Lusatia accelerated.     

上海陆家嘴地区回灌试验分析

地下水回灌试验表明地下水水位对地面沉降有直接的影响,当进行地下水回灌时,地下水位逐渐回升,地面产生回弹。地面沉降规律与地下水水位变化较为一致,水位回升越大,地面回弹也越大。地面沉降和回弹较地下水水位的变化有一定的滞后性。地下水水位的变化与所在点周围的地面沉降具有较好的时空对应关系。基坑降水设计可采取地表水回灌措施有效抑制地下工程施工过程中因工程降水引起地下水变化引起的地面沉降,基坑降水中选择坑内降水井抽出的地下水对坑外回灌井通过密闭管道在还原环境下实施回灌。     

Reducing the environmental impacts of reverse osmosis desalination by using brackish groundwater resources

The aim of the present work is to find out whether or not, and to what extent, the environmental impacts of reverse osmosis desalination are reduced when brackish groundwater is used instead of sea water. In order to answer this question, the Life-Cycle Assessment (LCA) methodology is used, and two water production plants are compared. The brackish groundwater scenario is based on a plant located in Almería (southern Spain), while the sea water scenario is based on literature data. Four impact categories and two environmental indicators, one of them related to brine discharge, are included. The results show that the key life-cycle issue of brackish groundwater desalination is electricity consumption, and since this is substantially reduced with regard to using sea water, the life-cycle impacts are found to be almost 50% lower. An uncertainty analysis based on Monte-Carlo simulation shows that these environmental savings are significant for all impact categories. Potential local impacts provoked by brine discharge are also found to be lower, due to a reduced content of salts. It is concluded that, when and wherever possible, exploitation of brackish groundwater resources should be assigned priority to sea water resources as an input for reverse osmosis desalination, although it must be taken into account that groundwater, as opposed to sea water, is a limited resource.     

降承压水引起地表沉降的预估与实测对比研究

随着基坑工程不断向大深度、大面积方向发展,承压水降水引起的环境影响日益明显。本文采用以现场抽水试验参数为依据的数值模拟法对承压水降水引起的地表沉降进行了预测,并与基坑开挖和降水期间引起的地表总沉降进行了对比研究。实例分析结果表明,在基坑开挖和降水期间,承压水降水引起的沉降量占总沉降的比重比较大(约占30%);以现场抽水试验参数为依据的数值模拟法能较好地还原降水过程中地下水渗流场的分布形式、降深影响范围和沉降影响范围,为承压水降水引起的地表沉降研究提供了重要的工程资料和分析依据。     

A mined underground space master plan for Minneapolis, Minnesota—Part II

This second of a two-part article focuses on groundwater issues affecting the development of a mined underground space master plan for Minneapolis (Minnesota, U.S.A.). In the geologic formation underlying Minneapolis, there are generally two water tables: (1) a perched water table in the limestone that extends, at some locations, into the glacial drift; and (2) a water table in the sandstone. [Geology of the area is described in Part I of this article in T&UST 5:3.] A specific mined underground space development in Minneapolis could require some dewatering of the underground formation, affect a perched water table above the project, or involve other groundwater impacts. The authors examine the groundwater issues and regulations, and make recommendations about them as they relate to possible future underground development of the area.     

European case studies supporting the derivation of natural background levels and groundwater threshold values for the protection of dependent ecosystems and human health

The EU Water Framework and Groundwater directives stipulate that EU member states have to assess groundwater chemical status by the use of groundwater threshold values derived for the protection of dependent ecosystems and human health. This paper presents a synthesis of main results of 14 European case studies evaluating a methodology for derivation of natural background levels (NBLs) and groundwater threshold values (TVs) proposed by the EU research project "BRIDGE". The 14 investigated groundwater bodies were selected to represent as many aquifer types, climate settings and European ecoregions as possible within the project group that included partners from 17 EU countries. The selected case study sites include transboundary groundwater bodies, EU Pilot River Basins and other important groundwater systems. Some are known to interact with associated ecosystems, while others do not. The proposed method derives groundwater threshold values based on environmental objectives for dependent ecosystems or groundwater "itself" using relevant reference criteria such as natural background levels, environmental quality standards and drinking water standards. Derived groundwater threshold values for dissolved Cl and As applying drinking water standards as examples of reference values, are compared for all 14 case studies. Additionally, more detailed analyses are conducted for the Odense Pilot River Basin and the Vouga River Basin, where groundwater threshold values for N and P and Cl, As, Cd, Ni, Pb, and Zn, respectively, are derived based on environmental objectives and quality standards for groundwater dependent ecosystems. Results demonstrate that the proposed methodology is operational and may be used to protect human health and the environment. Further they show that groundwater threshold values derived from environmental objectives and environmental quality standards for dependent ecosystems in some cases may be significantly lower than drinking water standards, e.g. for nitrate.     

'To Pump or Not to Pump' Cost-Benefit Analysis of Future Environmental Management Options for the Abandoned Durham Coalfield

Deep mining activity has totally ceased in the Durham coalfield, and withdrawal of the regional dewatering scheme is being contemplated. Consequent groundwater rebound is expected to have severe and expensive environmental consequences, which could only be entirely avoided through indefinite pumping. However, continued pumping is expensive, at about $1 million/annum. The options of either abandoning or continuing pumping have differing time streams of future costs and, consequently, direct comparison of the expenditures involved is difficult. Both options are therefore analysed using economic evaluation criteria in order to determine the lowest cost alternative for the future. The overall outcome of the economic analysis, using both net present value and equivalent annual cost criteria, demonstrates that the option of continued pumping is less expensive than the option of abandoning pumping in all cases.     

粉土地基真空井点降水效果及土颗粒迁移效应

为研究粉土地基中群井条件下的真空井点降水过程及降水效果,进行了现场试验。试验表明,群井条件下,随井点间距的减小和井点深度的增大,水位下降要快得多。由于群井降水具有显著的三维空间效应,所以,群井降水引起的地下水位降低要比单排井点和单井点更为显著,同时,降水引起的地下水位下降范围也更大,这一效应随井点深度的增加更为明显。由现场取得原状土样进行的室内渗透试验表明,连续抽水后,在真空和水力的双重作用下,土层中的土颗粒有明显的迁移,导致地层中土的孔隙比增大,渗透系数也明显增大。     

复杂巨厚第四纪松散沉积层地区深基坑降水三维渗流场数值模拟——以上海地铁4~#线董家渡段隧道修复基坑降水为例

针对长江三角洲地区分布有复杂巨厚第四纪松散沉积层,且具有较高的承压水位,其深基坑降水的模拟、预测难度大。以上海地铁4#线董家渡段隧道修复基坑降水为例,建立基坑降水三维渗流模型,并采用有限差分数值模拟方法,模拟在多层含水层复合存在、含水层最深底板埋深达150 m、基坑周围挡水连续墙埋深达65 m、抽水井埋深达59 m、抽水井过滤器埋深为44～59 m及30口抽水井联合降水情况下,基坑中心下伏第2承压含水层中部降压段水位降至埋深43.35 m时的地下水复杂流动状态。经后续工程验证,该结果正确、可靠,该理论用于模拟预测此类地区深基坑降水引起的地下水流场变化具有较高的可信度。     

江苏银行深基坑防水技术研究

通过对深基坑防水技术的研究,介绍了水体的变化对工程的安全、质量、进度、成本等多方面的影响,阐明了在深基坑施工过程中,采取的降排水、地下水处理等防护措施的重要性。     

武汉地区某地铁车站非落底式止水帷幕深基坑降水设计

针对武汉地区的长江I级阶地冲洪积地层,基坑工程一般采用落底式竖向帷幕治理地下水,但落底式竖向帷幕工程造价昂贵,施工工期较长,施工质量难于保证。论文结合武汉地铁2号线中山公园站基坑工程,介绍了非落底式止水帷幕结合深井(管井)减压疏干降水技术治理地下水的方案。通过具体工程研究了基坑涌水量的预测及降水设计、降水预测及降水动态控制、基坑降水对周边环境的影响预测等实际问题,为类似工程设计提供参考。     

CO<Subscript>2</Subscript> Storage related Groundwater Impacts and Protection

Injection of CO₂ into the deep subsurface will affect physical and chemical conditions in the storage environment. Hence, geological CO₂ storage can have potential impacts on groundwater resources. Shallow freshwater can only be affected if leakage pathways facilitate the ascent of CO₂ or saline formation water. Leakage associated with CO₂ storage cannot be excluded, but potential environmental impacts could be reduced by selecting suitable storage locations. In the framework of risk assessment, testing of models and scenarios against operational data has to be performed repeatedly in order to predict the long-term fate of CO₂. Monitoring of a storage site should reveal any deviations from expected storage performance, so that corrective measures can be taken. Comprehensive R & D activities and experience from several storage projects will enhance the state of knowledge on geological CO₂ storage, thus enabling safe storage operations at well-characterised and carefully selected storage sites while meeting the requirements of groundwater protection.     

Ground anchors in an aggressive hydro-environment

Kuwait City is a Middle Eastern coastal city characterized by arid conditions with shallow, saline groundwater. As some parts of the new ring road development were below the ground water level, 5,000 anchors were incorporated in the design to restrain the road against hydrostatic uplift pressures. About 750 anchors were only partially completed when they were inundated with aggressive groundwater for a period of about 2 years when dewatering was temporarily abandoned as a result of the Gulf War in 1990. Subsequently, physical, metallurgical and strength tests were undertaken to assess both the degree of corrosion and the long-term integrity of these partially completed anchors. The paper discusses the testing, the remedial measures and the long-term monitoring system. It was decided to keep some of the dewatering wells as a precautionary standby in case of future problems.     

Fundamental aspects of sludge filtration and expression

The filtration and expression behaviour of sewage sludge is discussed. Due to the increase of costs for controlled dumping and transport and more severe environmental legislation the need for decreased sludge volumes is rising. Filtration and expression are the cheapest dewatering operations and it is therefore desirable to remove the maximal feasible amount of water by mechanical dewatering. High dry solids contents of 35–40 wt% can already be reached at pressures of 300–400 kPa and optimal flocculation conditions; however at pressures of 6–10 MPa dry solids contents of 60 wt% can be reached. Further the modelling of the dewatering is discussed; model and experiment show acceptable agreement.