连拱隧道施工对洞口仰坡影响的三维数值分析

以江西某高速公路一浅埋偏压连拱隧道为例,采用Marc有限元程序对其出口段进行了动态施工的三维数值模拟.从施工过程中的应力集中、塑性区的分布形态和发展规律、仰坡轴向地表位移的分布特征等方面,系统研究了偏压连拱隧道施工对强风化岩体洞口仰坡的影响作用机制.结果表明:在模拟施工过程中塑性区和应力集中区只出现在洞体附近,可能的仰坡失稳往往是隧道施工失稳的累进性响应;洞口仰坡的轴向水平位移前缘大、后缘小,垂直位移后缘大、前缘小;隧道上方和近山脊一侧仰坡位移比近山谷一侧大,仰坡失稳往往从隧道上方和埋深较大一侧开始.     

Lippmann Diagrams: Theory and Application to Carbonate Systems

Since 1980 when F. Lippmann's seminal paper appeared, ourunderstanding of solubility equilibria involving ionic solidsolutions has been advanced by theoretical considerations as wellas careful experimental studies designed to determine excess Gibbsfunctions. A unified theory of solid-solution aqueous-solutionequilibria as well as the thermodynamic background of thephenomenon of ``stoichiometric saturation' are reviewed.It is shown that Lippmann diagrams effectively summarize thethermodynamic basis of solid-solute aqueous-solution equilibria ofsparingly soluble metal carbonate systems. Clearly, the predictivepower of these diagrams may be limited due to kineticrestrictions. Only when dissolution and precipitation areessentially reversible, favourable conditions to synthesizehomogeneous solid phases can be derived from studies of equilibria.     

Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil, Dalarna, Sweden

This study investigates the retention of heavy metals in secondary precipitates from a sulfidic mine rock dump and underlying podzolic soils by means of mineralogical and chemical extraction methods. The rock dump, which is at least 50 years old, consists of a 5–10-cm-thick leached zone and an underlying 110–115-cm-thick accumulation zone. Optical microscopy and electron microprobe analyses confirm that pyrrhotite weathering has proceeded much further in the leached horizon relative to the accumulation horizon. The weathering of sulfides in the leached zone has resulted in the migration of most heavy metals to the accumulation zone or underlying soils, where they are retained in more stable phases such as secondary ferric minerals, including goethite and jarosite. Some metals are temporarily retained in hydrated ferrous sulfates (e.g., melanterite, rozenite). Received: 28 October 1996 · Accepted: 24 February 1997     

中国主要有色金属矿产的供需形势

国内有色金属产消高速增长,国产原料供应严重短缺。国内铜产量约70%、铝产量约50%、铅产量约30%、锌产量约10%、镍产量约40%依靠进口原料生产,优势矿产锡也开始步入进口原料的行列。矿山开采消耗有色金属储量的速度快于矿产勘查新增储量的速度,矿产资源紧张形势依然严峻。应实施矿产资源全球配置战略,同时继续加强对国内矿产资源的勘查力度,提高国内资源的保证程度。     

Variation in DOC and trace metal concentration along the heavily urbanized basin in Kathmandu Valley,Nepal

Water samples were analyzed for DOC and trace metals from Bagmati River within Kathmandu valley, Nepal, to understand the variation trends of DOC and trace metals and their relationship along the drainage network. The variability in organic matter and wastewater input within the Bagmati drainage basin appeared to control DOC and most of the trace metal concentration. The large input of organic matter and wastewater creates anoxic condition by consuming dissolved oxygen and releasing higher concentrations of DOC, trace elements such as nickel, arsenic, barium, cadmium, and copper with downstream distance. Concentrations of DOC and trace metals like barium and zinc showed strong relationships with human population density and suggest that human activities have strong control on these parameters along the drainage network. The DOC and most of the trace metal concentration increased with downstream distance and appeared to be directly associated with human activities. The variation trends of most of the trace metals appeared to be the same; however, concentration varied widely. Inputs of organic matter and wastewater due to human activities appeared directly to be associated for the variation of DOC and trace metals along the Bagmati drainage network within Kathmandu valley.     

某金矿区农田土壤重金属元素Pb的累积速率

以某金矿区农田土壤重金属Pb为研究对象,分别以2004和2012年采集样品的测试结果作为计算农田土壤重金属Pb累积速率的依据,以2004—2012年作为计算时间区间,以农田土壤重金属Pb的累积速率为研究内容,采用对比分析方法,分析区域Pb的累积速率特征,阐明人类工程活动极大地影响着农田土壤重金属Pb的累积过程。研究结果表明,全区农田土壤Pb平均累积速率为31.8mg/kg·a-1。选取选矿厂、冶炼厂、尾矿库、污水灌溉区、车载尾矿弃渣等典型污染源,对周边农田土壤Pb累积的时空变化特征进行分析。结果显示,选矿厂对农田土壤Pb累积的影响最大,其周边农田土壤Pb累积速率相当于全区Pb累积速率的4倍,该结论对防治重金属污染及保障人体健康具有实际指导意义。     

典型矿区深层地下水重金属含量特征及健康风险评价——以皖北矿区为例

以皖北矿区为例,分析测试了不同含水层(松散、煤系、太灰、奥灰)中的6种重金属元素(Cd、Cr、Cu、Zn、Pb、Ni),对其含量特征及健康风险评价进行了研究。结果表明,6种重金属在不同含水层含量大小次序各不一样,从整体来看,研究区地下水中所测重金属含量依次为NiZnPbCuCdCr,与太灰水一致;整体地下水中Cr、Cu和Zn均未超过(GB/T14848—93)中Ⅲ类水质标准,Cd、Pb和Ni有部分水样超过标准限值。化学致癌物Cd和Cr在各含水层所致健康危害风险值数量级在10-6~10-4 a-1,Cr健康风险值在各含水层中均大于Cd,Cr在煤系含水层危害风险值(1.29×10-4 a-1)已超过美国环境保护局(USEPA)最大可接受风险(1×10-4 a-1),为研究区首要的环境健康风险管理控制指标。化学非致癌物Cu、Zn、Pb、Ni四种重金属健康危害风险值较小,数量级在10–11~10-8 a-1,Pb和Ni健康危害风险值相对较高,也应引起重视。各含水层总的健康风险值大小次序为:煤系太灰奥灰松散,前三者已超过国际辐射防护委员会(ICRP)推荐的(5×10-5 a-1)最大可接受风险,其中煤系含水层总的健康风险值为1.46×10-4 a-1,已超过USEPA(1×10-4 a-1)推荐的最大可接受风险。对矿区深层地下水开展重金属含量分析和健康风险评价,可为地下水水资源的开采利用和保护提供参考。     

秦岭山阳-柞水矿集区150~140Ma斑岩-矽卡岩型CuMoFe(Au)矿床成矿作用研究

秦岭造山带内的山阳-柞水古生代弧前盆地中出露有池沟、小河口、冷水沟、园子街、下官坊及双元沟等CuMo、CuFe(Au)矿床,与这些矿床具有成因联系的岩体为形成于150~140Ma的高钾钙碱性和钾玄岩系列花岗岩,为华北和扬子大陆碰撞后伸展阶段壳、幔混合岩浆的产物。矿化主要发生在岩体与泥盆、石炭纪地层中碳酸盐岩的接触带附近,主要类型为矽卡岩型,少量为斑岩型,部分矿床具有统一的矽卡岩-斑岩型成矿系统,矿化组合主要为CuMo、CuFe(Au)和Cu矿化。外接触带主要发育有矽卡岩和角岩化蚀变,内接触带主要为岩体内部的硅化、钾化、绢云母化、绿泥石化及粘土化,内矽卡岩不发育。矽卡岩矿物主要有石榴石、透辉石、绿帘石、透闪石,阳起石等,其中石榴子石主要为钙铁榴石和钙铝榴石,透辉石是辉石的主体,早期形成的石榴石和透辉石等无水矿物组合常被后期的绿帘石、透闪石和阳起石等含水矿物及石英、方解石等所交代。金属矿物比较简单,最主要的含铜矿物为黄铜矿和斑铜矿,铁矿化主要为磁铁矿和镜铁矿。尽管这些矿床以矽卡岩型矿化为主,但部分矿床中已发现有斑岩型矿化和蚀变特征,这可能暗示了该区可能具有统一的矽卡岩-斑岩型成矿系统,进而表明山阳-柞水矿集区深部具有寻找斑岩型矿床的巨大潜力。     

A neurocomputing approach to the forecasting of monthly maximum temperature over Kolkata, India using total ozone concentration as predictor

The association between the monthly total ozone concentration and monthly maximum temperature over Kolkata (22.56° N, 88.30° E), India, has been explored in this paper. For this, the predictability of monthly maximum temperature based on the total ozone as predictor is investigated using Artificial Neural Network. The presence of persistence and similar cyclic patterns are revealed through autocorrelation and cross-correlation coefficients. Common cycles of length 12 and 6 have been identified through periodogram. Hence, a predictive model has been generated by Artificial Neural Network in the form of Multi Layer Perceptron (MLP) using scaled conjugate gradient learning with sigmoid non-linearity. After training and testing the network, an MLP with total ozone of month n as predictor and maximum temperature of month (n + 1) as the target output is found as the best model. Performance of the model has been judged statistically. Finally, the MLP model has been compared with linear and non-linear regressions and the efficiency of MLP has been established over the regression models.     

关键金属元素分析测试技术方法应用进展

以稀有、稀散、稀土、铂族元素为主体的战略性关键金属矿产资源,在新材料、新能源和信息技术等新兴产业中发挥着越来越关键的作用。随着我国关键矿产资源地质调查的不断深入,关键金属元素以其赋存基体复杂、不同矿物含量差异大、化学性质不稳定等特点对分析测试技术提出了新的挑战。本文根据化学组成不同,对关键金属元素主要赋存基体进行了分类,主要分为硅酸盐、碳酸盐、硫酸盐、钨酸盐、磷酸盐、氧化物、硫化物、卤化物等。对于不同的基体岩石矿物,通常采用酸溶法(硝酸-氢氟酸组合、王水)或碱熔法等传统溶样方法进行化学消解。评述了当前关键金属元素测试常用的电子探针、电感耦合等离子体质谱、电感耦合等离子体发射光谱、X射线荧光光谱等仪器的特点及应用,总结了关键金属元素分析过程中出现的样品难溶解、回收率不完全、测试过程氧化物和同质异位素干扰、样品和标准基体不一致等常见问题,并提出了相应的解决方案。微区原位分析凭借其高效率、低成本、高空间分辨率的优势,以及野外现场分析凭借其简单快速、贴近野外工作的特点是关键金属元素测试技术发展的主要趋势。