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。     

周期性排桩设计频段隔振原理性试验研究

针对目前基于带隙理论开展的周期性隔振排桩性能研究偏重于解析理论分析和数值仿真计算的现状,采用原理性试验的方法,验证了周期性隔振排桩的衰减域特性。试验设计了4种工况：分别考虑了空心钢管桩和填土钢管桩两种排桩类型,以及六角晶格和正方晶格两种周期性布置方式。激振采用脉冲荷载激励,将隔振工况与无桩基本工况进行比较,对周期性排桩的振动衰减域进行了测试和分析,并与带隙理论计算的频率带隙结果进行对比。研究表明：在理论计算带隙范围内,各工况下实测衰减水平均在50%以上,最高达到98%。表明了周期排桩对特定频带的振动阻隔实际效果明显,隔振表现突出,证实了理论分析的有效性。周期排桩对水平方向的振动衰减优于竖直方向;从趋势上看,在其他条件相同时,六角晶格布置的周期排桩,其振动衰减水平优于正方晶格布置;桩内填土可有效增加六角晶格布置钢管桩的首阶带隙及衰减域宽度,有效降低正方晶格布置钢管桩的首阶带隙及衰减域起始频率。对应于试验的工程实际尺寸在0～80 Hz频段内出现多条带隙,并且最低可达20 Hz以下,这表明,基于带隙理论进行周期隔振排桩设计,在地铁列车振动环境影响的特征频段隔离或衰减中,具有广泛的应用前景。     

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。     

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.     

Harvesting flow-induced vibration using a highly flexible piezoelectric energy device

Energy harvesting is a topic of global interest in both academic research and practical application across many fields. The main concept in energy harvesting is to convert wasted ambient energy into useful electrical energy. In particular, piezoelectric materials can be used to convert strain energy into electric power directly, and piezoelectric materials can be used to harvest external vibration forces.This paper proposes and develops a highly flexible piezoelectric energy device (FPED) to harvest flow-induced vibration by converting ambient kinetic energy such as ocean, current and wind energy into electric power. The energy harvesting device uses piezoelectric layers (e.g. PVDF) and elastomer materials (e.g. rubber or silicone) to achieve high electric performance and efficiency. The design of the FPED was optimized by considering the aspect ratio, support system, initial tension and incorporates a bluff body to generate turbulence. A theoretical model based on the transfer matrix method was used with the initial tension force and natural frequency of the harvester. The model demonstrated the maximum electric performance and optimized the structural layers and size under the parameter studies. Numerical and experimental results proved the potential of the highly flexible piezoelectric energy device to convert ambient kinetic energy from flow-induced vibration into useful electrical energy.     

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。     

Effect of Peak Perforation on Flow Past A Conic Cylinder at Re=100: Drag, Lift and Strouhal Number

A flow past a circular-section cylinder with a perforated conic shroud, in which the perforation is located at the peak of the conic disturbance as the shroud installed on the cylinder and uniformly distributed with several circular holes, is numerically simulated at a Reynolds number of 100. Two factors in the perforation are taken into account, i.e. the attack angle relative to the direction of incoming flow and diameter of holes. The effect of such perforation on the drag, lift and vortex-shedding frequency is mainly investigated. Results have shown that variation of the attack angle has a little effect, especially on the drag and vortex-shedding frequency, except in certain cases due to the varied vortex-shedding patterns in the near wake. The increasing hole diameter still exhibits a little effect on the drag and frequency of vortex shedding, but really reduces the lift, in particular at larger wavelength, such as the lift reduction reaching almost 66%–68% after introducing the perforation.     

Multiple Tuned Mass Damper Based Vibration Mitigation of Offshore Wind Turbine Considering Soil-Structure Interaction

The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.