热带准两年振荡影响北半球冬季大气环流的诊断分析

利用NCEP/NCAR再分析资料,首先讨论了热带纬向风准两年振荡(QBO)的东、西风位相的划分标准.结果发现,赤道50 hPa的风与西风深厚度关系最密切,即赤道50 hPa的纬向平均风为西(东)风时往往代表平流层下层为一层深厚的西(东)风.在此基础上诊断分析了1958/1959～1997/1998年共40个冬季中热带纬向风QBO对北半球中高纬度地区纬向平均环流和准定常行星波传播的影响.诊断分析表明,热带QBO对北半球冬季大气环流的影响主要表现在平流层和对流层上层.热带QBO的东风位相年与西风位相年相比,中高纬地区的绕极西风环流明显减弱,中低纬地区则出现相反变化,从而在平流层的纬向平均环流分布上呈现偶极子形式.纬向平均流的这种年际变化可以很好地用中高纬度准定常行星波传播的异常加以解释,QBO的东风位相年和西风位相年相比,中高纬准定常行星波向极地的传播更强,从而在高纬度平流层产生异常的E-P通量辐合,波-流相互作用的结果使得西风减弱.但是热带纬向风QBO的影响在1958/1959～1997/1998年的前后20年有所差异.后20年相对于前20年而言,东西风位相的差异有所减小,Hol-ton-Tan振荡明显减弱;就行星波传播而言,东风位相年下,前20年行星波向上传播较弱,而后20年则以大约70°N为分界点,以南向上传播较强,以北向上传播较弱.这种差异可能跟中高纬度纬向西风的自身变化有关.     

考虑地层变异特征一致性的围岩变形不确定性分析

目前地层变异性分析大多基于地层重复性沉积和变异特征一致性假设,而未考虑地质构造和风化作用的影响,忽略了地层变异性特征一致性的检验。为此,提出地层变异特征一致性的检验和分区方法,采用岩土相局部状态转移概率矩阵的相关系数作为一致性的定量判据,基于耦合Markov链模型模拟地层分布,并通过Monte Carlo方法分析隧道围岩变形的不确定性。利用青岛轨道交通某斜井的地质钻孔数据,探讨了地层变异特征一致性对地层分布和变形模拟精度的影响,分析了所提方法的有效性。结果表明,当地质构造和风化作用导致地层变异特征不一致时,增加钻孔数量无法提高地层分布模拟精度,采用所提方法对地层变异特征一致性检验并分区后,可避免状态转移概率矩阵中局部地层分布特征缺失的问题,提高围岩变形不确定性分析的准确性。     

碱熔沉淀分离-电感耦合等离子体质谱法测定伴生重晶石稀土矿中的稀土元素

采用电感耦合等离子体质谱法(ICP-MS)测定伴生重晶石轻稀土矿中的稀土元素时,Ba以及轻稀土元素La、Ce、Pr、Nd、Sm等对中重稀土造成严重的质谱重叠干扰,因此在保证矿石完全消解的同时,若能选择合适的前处理方法实现目标元素与基体的有效分离,将有利于减少质谱干扰。本文采用过氧化钠-碳酸钠熔融分解伴生重晶石的稀土矿样品,熔融物用三乙醇胺溶液提取,将沉淀过滤去除硅、铁、锰、铝等大量基体元素,而稀土元素与钡、锶、钙等留存于沉淀中,沉淀经盐酸溶解后再用氨水进行二次沉淀,将稀土元素与伴生的高含量钡、锶、钙等元素分离,分离率超过96%,从而极大地降低了由钡的氧化物和氢氧化物对~(153)Eu等元素质量数的质谱干扰。轻稀土元素对中重稀土元素的干扰则通过测定高浓度的单元素标准溶液在m/z 138～175处的表观浓度来计算干扰校正系数,对干扰量进行扣除校正。该方法通过稀土矿石标准物质GBW07187、GBW07188验证,测定值与认定值的相对误差10%;应用于伴生重晶石稀土矿石实际样品分析,相对标准偏差(RSD,n=12)为0.5%～4.6%,证明了本方法可用于分析高钡矿石中的稀土元素。     

振荡交换-抽滤淋洗结合凯氏定氮法快速测定土壤中的阳离子交换量

测定土壤阳离子交换量(CEC)的行业标准方法(LY/T1243—1999)是采取离心分离结合手工蒸馏进行滴定,耗时长、操作繁琐。为了缩短反应时间,提高检测效率,本文利用乙酸铵对酸性和中性土壤进行处理,用氯化铵-乙酸铵对石灰性土壤进行处理,应用振荡和抽滤装置快速交换和清洗阳离子,通过全自动凯氏定氮仪对吸附的铵根离子进行测定,由此计算CEC值。结果表明:在最佳的振荡和蒸馏时间、滴定酸浓度、指示剂配比等实验条件下,一个批次样品(100件)的分析流程仅需要12h,比传统方法检测时间缩短近80%。经国家标准物质验证,测定结果与推荐值相符,5次测定的相对标准偏差均小于1. 5%。本方法免去了多次离心分离操作,解决了待测成分损失、CEC测定值偏低的问题,提高了检测效率和准确度,较林业标准方法的成本低,可操作性强,适用于土壤环境质量评价、地区土壤抽样调查等大批量土壤样品分析。     

钻井船插桩CEL数值模拟中的若干问题分析

依据模拟钻井船在不同场地条件下贯入阻力的离心模型试验结果及具体工程实例,对利用耦合欧拉-拉格朗日（CEL）有限元方法模拟钻井船在黏土、砂土、黏土下覆砂土、砂土下覆黏土及成层土场地插桩过程时,影响贯入阻力计算结果的几个因素进行了研究。结果表明,对于不同土层场地条件,有限元模型中欧拉区域范围对贯入阻力几乎没有影响。为确保CEL数值结果的精度,有限元建模时靠近桩靴部分设置为细网格区域,以外区域设置为粗网格区域;对于不同土层场地条件,减小细网格尺寸及增大细网格范围可以减小贯入阻力的振荡情况;经比较总结,细网格尺寸建议取0.05倍桩靴直径,细网格范围建议取2倍桩靴直径。采用位移控制模拟钻井船插桩时,桩靴贯入速率对黏土场地的贯入阻力影响较小,对砂土下覆黏土场地的贯入阻力影响很大,对一般成层土场地的贯入阻力有一定影响。经比较总结,建议在研究钻井船在不同土层场地的计算贯入阻力时,有限元模型的桩靴贯入速率取0.2 m/s。     

Textures and U-W-Sn-Mo signatures in hematite from the Olympic Dam Cu-U-Au-Ag deposit,South Australia: Defining the archetype for IOCG deposits

The textural characteristics and trace element geochemistry of hematite with U-W-Sn-Mo signatures from the Cu-U-Au-Ag orebody at Olympic Dam, South Australia, are documented. Olympic Dam is the archetype for iron-oxide copper–gold (IOCG) deposits where hematite is by far the most abundant mineral in the orebody. The deposit is located within hematite-bearing breccias (>5% Fe) hosted by the ∼1.6 Ga Roxby Downs Granite (RDG). Although such breccias are mostly derived from RDG, they also include volcanic clasts and sedimentary rocks. Samples cover the ∼6 km strike length and ∼2 km vertical extent of mineralisation, including hematite from the aforementioned lithologies. Hematite with U-W-Sn-Mo (‘granitophile’ elements) signatures is recognised throughout all lithologies and parts of the deposit. Hematite enriched in granitophile elements is represented by a variety of textures, of which zoned hematite, defined by oscillatory zonation patterns, is the most prominent and can be tied to the age of the RDG, and thus initiation of the IOCG system as confirmed by published U-Pb geochronology. Other categories of hematite with granitophile signatures include hematite resulting from replacement of pre-existing minerals (e.g., carbonates and feldspars), as well as replacement of previous oscillatory-zoned hematites. Matrix and vacuole filling hematite from volcanoclastic-dominated intervals also carry ‘granitophile’ signatures. In addition, some colloform types which likely post-date primary IOCG mineralisation are also rich in ‘granitophile’ elements. Trace element mapping and spot analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) defines complex trace element signatures of hematite, which, in addition to the ‘granitophile’ elements, also comprise rare earth elements, high field strength elements, chalcogens and transition metals.The distinct geochemical signature, characterised by enrichment in the ‘granitophile’ elements (up to wt% levels of U and W within individual zones, and up to thousands of ppm Mo and Sn) prevails throughout the hematite in the deposit irrespective of textures. Iron-oxides have been repeatedly formed, reworked and overprinted by subsequent cycles of brecciation, fluid-mineral reaction, remobilization, element redistribution and recrystallisation. Coupled dissolution-replacement reactions are discussed as having played a major role in the modification of textural and geochemical patterns in hematite, but also allow for widespread preservation of primary geochemical signatures. Despite its simple chemistry, the crystal-structural modularity of hematite can adapt and retain evolving fluid signatures. The reported trace element signatures are fully concordant with conceptual frameworks for the genesis of IOCG systems, and may be an inherent, albeit hitherto under-reported characteristic of other IOCG systems. Hematite is probably by far the most important W-, Sn- and Mo-bearing phase in the deposit by mass.     

TLP风机基础二阶动力响应研究

针对概念设计的位于南海的三腿TLP浮式风机基础,应用基于水动力与空气动力耦合的FAST程序在时域内开展了风机基础的动力响应分析。结果表明,风载荷对TLP风机基础六个自由度的动力响应,尤其是纵摇影响显著。由于耦合作用,二阶波浪力进一步增大了基础的纵荡、横摇和艏摇响应。谱密度分析表明,风载荷及二阶波浪力显著地增大了浮式基础水平面内的低频运动。此外,基于风机基础运动时程,应用ORCAFLEX软件开展了时域内筋腱的顶部张力特性分析,结果表明,风载荷和二阶波浪力增大了筋腱顶张力幅值。     

Three-dimensional finite element analysis for soil slopes stabilisation using piles

This paper presents the analytical methods of slope-stabilising piles using the three-dimensional (3-D) finite element (FE) analysis with the strength reduction method (SRM). This 3-D FE model is employed to overcome the limitations observed in two-dimensional (2-D) FE analysis. The solutions obtained from 3-D FE analyses are verified to be less conservative in this paper. The 3-D analysis is considered to be of particular importance to pile-slope problems. The soil that flows between piles cannot be taken account properly in the 2-D FE analysis. The method adopted in this paper can avoid the assumption of soil movement and the pressure distribution along the piles subjected to soil movement. The numerical analysis employs the Mohr–Coulomb failure criterion with the strength reduction technique for soil and an elastic member for piles. The spacing effect of the pile is considered in the 3-D model, the S/D (S: centre to centre, D: diameter of pile) ratio, equal to 4.0, is found to be equivalent to the single pile stabilisation. The middle portion of the slope is identified as the optimal location to place the piles. The proper length of the pile, which can be used to stabilise the slope, is also examined using 3-D FE analyses. It is concluded that L/H greater or equal 0.70 is recommended (L: pile length, H: slope height). The numerical analyses are conducted based on a coupled analysis, which simultaneously considers both the slope stability and the pile response. The failure mechanisms of the pile-slope system subjected to the pile locations, pile head conditions and pile length are each discussed. The contact pressure, shear force and moment along the piles are presented to illustrate the pile stabilising mechanism herein.     

Application study of coupled model between reservoir organic pollutant BOD5-DO and temperature

The BOD5-DO (Biochemical Oxygen Demand in five days and Dissolved Oxygen) are important indexes that reflect the organic pollution extent of water,but the variation of the indexes is closely related with water temperature.The study on the coupled mathematical model reflecting the BOD5-DO with temperature is the key to reveal the mechanism of the migration and distribution of BOD5-DO in the water.The authors presented 1-D mathematical model for the three variables in vertical direction,and gave accurate solution for the equations under steady state,the relation among the variables and the method for solving BOD5-DO concentrations at different depth and temperature.     

双向振动条件下的饱和砂土动强度特性试验研究

利用全自动静动三轴双向耦合剪切仪,分别在均等固结和非均等固结条件下,进行了福建标准砂的动三轴不排水剪切试验,对比分析了轴向振动、径向振动、相位差分别为0°和180°的轴向-径向耦合振动等不同振动方式对饱和砂土动力特性的影响。试验结果表明,无论是均等固结还是非均等固结条件下,只要在最大剪应力面上的动剪应力水平相同,4种剪切方式对动应力-应变关系及动强度的影响都并不显著。