用VOF方法模拟静止浅水环境中的垂向紊动射流

以k-ε紊流模型为基础,针对浅水环境垂向射流的水面会有明显突起情况,采用VOF(Volume of Fluid)方法追踪自由面,建立了适合浅水环境垂向平面紊动射流的二维数学模型.对不同入射速度、水深、入射口宽度组合进行了大量的数值模拟实验,对整个流场的分布作了分析,发现自由面的分布特点和速度矢量场的分布特点相对应;中轴线附近的自由面隆起具有自相似性,文中给出了拟合表达式;由于水面的阻滞,中轴线上垂向速度的衰减较自由射流快,衰减规律随水深和射流宽度而异.     

桥梁健康监测与评估中的静力水准技术研究

近年来,我国的桥梁建设事业发展迅速,在桥梁数量大幅增加的同时,其安全形势却较为严峻,因此,越来越多的人开始重视桥梁运营的安全性及耐久性.桥梁健康监测技术通过对桥梁结构的监控及评估,在桥梁运营状况发生异常时发出预警,能够为桥梁的维护及管理提供科学的指导和依据.而静力水准监测技术与传统的光学水准监测技术相比,具有实时性、高...     

线性参照系统下的嵌套金字塔模型构建

针对线性参照虚拟场景构建中缺乏有效的空间数据模型的问题,本文以金字塔模型、空间索引结构和动态分段等相关研究为基础,提出了线性参照系统下的嵌套金字塔模型构建方法.首先,结合线性场景数据特征,对动态分段技术进行拓展,增加垂直方向结构化金字塔模型;然后,将线性参照在多尺度下进行静态分段,对相互独立的弧段分别进行存储,构建静态...     

BDS-3新频点单点定位研究

针对目前有关北斗卫星导航系统(BDS-3)中MEO卫星(BDS-3M)增加的B1C、B2a新频点单点定位研究较少的现状,本文开展了基于新频点B1C、B2a的双频单点定位试验,结合国际GNSS监测评估系统(iGMAS)5个跟踪站连续10 d的数据,对BDS-3的新频点进行数据质量分析、双频伪距单点定位(SPP)和双频静态...     

一种顾及影像间位置关系的匀光方法

提出了基于矩匹配的色彩平衡算法,在顾及影像间位置关系的基础上将影像的均值和均方差映射到给定的数值,并且使不同区域的灰度均值和均方差近似相等,在尽量保持影像原有色调的条件下消除影像之间以及影像内部的色调和亮度差异。     

基于能量平衡的多年冻土区公路设计理论研究

青藏公路长期研究表明,青藏高原多年冻土公路工程空间效应敏感,主要表现为公路空间效应直接改变下伏冻土地基的天然能量平衡状态,继而引发一系列工程病害. 针对这一工程问题,提出多年冻土地区公路能量平衡设计理论,研究公路工程建设引发的多年冻土地基能量变化状态,平衡自然环境变化和工程建设等导致的外界“有害”能量导入与工程处置措施对冻土地基中“有害”能量导出之间相互关系,从空间和时间两个维度分析多年冻土地区公路工程的能量平衡过程. 据此,作为多年冻土公路工程的设计依据,将为青藏高原高速公路的科学设计提供理论支持.     

Mineralogy and geochemical behaviour during weathering of greenstone belt under tropical dry conditions in the extreme North Cameroon (Central Africa)

Mineralogy, major, trace and rare earth elements of a weathering profile developed on tertiary greenstone belt in the extreme North Cameroon are reported. The aim of which was to investigate mineralogical evolution and element mobilization and redistribution during weathering under dry tropical climate. The weathering profile consists of four main horizons: (1) a spheroidal weathering zone constituted by a corestone–shell complex, (2) a C horizon, (3) a Bw horizon and an Ah horizon. The results indicate that nontronite, a Fe-rich smectite, is the exclusive clay mineral formed in the exfoliated shells and the C horizon. It is associated with kaolinite in the upper horizons. The coexistence of these two clay minerals induced a decrease of CEC and pH which becomes neutral. The weathering index (WI) values reveal that weathering becomes more and more intensive from the corestone up to Bw horizon, which is the most weathered horizon in the weathering profile. Mass balance calculations, using Th as immobile element, indicate that Ti is quite mobile and that Al and Fe are relatively enriched at the bottom and strongly leached at the top of the profile. Alkalis and alkaline earth elements are strong leached through out the profile, except Ca which displays similar trend as Al and Fe. The same goes for LILE (Cs, Sr), TTE (Cr, Co, Ni) and HSFE (Y, Nb, Hf). In opposite, REE are depleted at the bottom and enriched in the upper horizons, with more enrichment for LREE than for HREE. It appears that weathering of greenstone belt causes a fractionation of HREE and induces a concentration of LREEs. Ce and Eu anomalies display opposite behaviour.     

胶东焦家金矿床热液蚀变作用

胶东作为中国最重要的金矿集区,区内大型-超大型金矿床集中产出,已探明金矿资源量占全国近1/3。其中,破碎带蚀变岩型金矿床是最重要的金矿床类型,占胶东已探明金矿资源量的90%以上,焦家金矿床是著名的"焦家式"破碎带蚀变岩型金矿的命名地,内发育大规模的绢英岩化蚀变带(宽20~200m)和钾化蚀变带(50~300m),蚀变岩型金矿体主要发育在焦家断裂带下盘的绢英岩化蚀变带中。本文通过详细的野外地质观测,查清了焦家金矿床蚀变类型及矿物组合特征,系统采集了不同蚀变类型的岩石样品,进行了岩石元素地球化学分析,运用质量平衡方法讨论了热液蚀变过程中元素迁移规律,初步探讨了焦家金矿床热液蚀变机理。其中,钾化蚀变是成矿前蚀变,钾化花岗岩常以团块状或角砾状残留于黄铁绢英岩和绢英岩内;黄铁绢英岩化和绢英岩化蚀变受焦家断裂及其下盘的次级断裂控制,其规模大小受断裂的规模控制;其中焦家主断裂下盘的绢英岩化蚀变带规模最大,一般宽10~200m;而次级断裂控制的绢英岩化蚀变带规模相对较小,一般以0.1~1m宽的脉状发育在钾化花岗岩内,指示绢英岩化蚀变晚于钾化蚀变。相对于黑云母花岗岩,不同蚀变带岩石普遍表现出高K2O、低Al2O3、CaO和Na2O,而不同蚀变岩石Si、Fe、Mg等元素各表现出不同特征。钾化带岩石表现为K2O的富集,而绢英岩带和黄铁绢英岩带岩石表现为MgO、Fe2O3增加的趋势。黑云母花岗岩发生钾化蚀变过程中,SiO2、K2O表现为明显的带入,指示在钾长石化过程中,流体为富硅的碱性氧化流体。在钾化花岗岩→黄铁绢英岩过程中,Fe2O3表现为明显的带入,可能是由于黑云母等暗色矿物的分解造成的;此外,亲硫元素(Au、Ag、As、Pb、Zn)均表现为带入,特别是成矿元素Au表现为明显的带入。结合本区金的来源可能部分为玲珑黑云母花岗岩,本研究认为钾化过程中的富硅碱性氧化流体通过交代蚀变反应使金从围岩中释放、成为高价态离子活化进入成矿流体,即分散还原态的金(Au0)被活化为氧化态(Au+、Au3+)以AuH3SiO4形式随热液迁移。在绢英岩化过程中,热液中的SiO2等组分损失,引起热液中的AuH3SiO4稳定性降低,造成AuH3SiO4分解,Fe2+、Fe3+被消耗形成黄铁矿,导致金大量沉淀和聚集沉淀,此时完成了金由活化→迁移→沉淀富集成矿。     

Skarn development from limestone adjacent to the Glenrock Granodiorite,Marulan Batholith,New South Wales,Australia

Skarns are developed over two temperature‐time intervals in calcite limestone adjacent to the southern extension of the Glenrock Granodiorite, a pluton of the Marulan Batholith, Southern Highlands, New South Wales. The initial volumetrically‐dominant prograde phase of skarn formation produced a suite comprising bimetasomatic skarn, including pyroxene endoskarn, potassic endoskarn and wollastonite‐bearing exoskarn, together with mineralogically‐zoned vein skarn, massive garnet‐pyroxene skarn and calcite‐vesuvianite skarn. Retrograde replacement is manifested by the development of hydrous silicate minerals, carbonate and cross‐cutting sulphide veinlets.

A genetic model is proposed to account for the development of bimetasomatic skarn in the deposit. Exoskarn geochemistry indicates addition of many components relative to an essentially pure limestone precursor, including Si, Al, Fe, Zr, Zn, S, Mn and Cu, negligible transfer of K, Na and Rb and loss of CO₂. Strontium and Ca loss from the parent limestone is indicated by mass balance calculations at constant volume.

Garnet and pyroxene compositions in the massive garnet‐pyroxene skarn range from Gr₃₀ to Gr₆₆ and Hd₆₁ to Hd₈₇, respectively. Compositions from Gr₆₇ to Gr₉₅ are typical of the vein skarn garnets. Chemical zonation patterns in garnet, pyroxene and vesuvianite are generally characterized by rim Fe depletion relative to cores of grains.

Prograde skarn probably formed at T = 500–580°C; P < 220 MPa. The massive garnet‐pyroxene skarn evolved under conditions of log fO₂ = ‐18.9 to ‐22.9 (assuming a constant fCO₂ of 20 MPa) within the fS₂ stability field of pyrrhotite. Retrograde skarn formed at T < 400°C, possibly under conditions of X_H2O < 0.01.

Vesuvianite plus wollastonite assemblages, present in exoskarn, probably attest to very water‐rich conditions. The marble wall rocks, isolated from the source of skarn‐forming fluids, probably evolved under conditions of minimum X_co2 >0.2. Low temperature CO₂ ‐rich fluid inclusions and prehnite (stable at X_co2 <0.01), present in the marble and skarn, respectively, suggest that substantial differences in X_co2: X_H2O were maintained during cooling.

Observed mineralogical and chemical zonation within the skarn reflects the complex interaction of T, P, fO₂, Xco₂ and other chemical variables such as a_SiO2 and a_Al2O3 throughout the skarn system. No single variable can account adequately for the mineralogical diversity observed in the skarn deposit.     

南京红层桩基持力层承载力初探

南京红层岩性复杂，桩基持力层承载力难确定。依据南京某工程勘察资料，建立南京红层泥岩、泥质粉砂岩不同互层情况的地质模型，运用FLAC3D软件分析，并与载荷板试验结果进行对比表明：桩基持力层应选择在厚度大于两倍桩径的泥质粉砂岩地层上，避免放置于泥岩地层；载荷板试验结果偏于保守，设计时可以把这部分作为安全储备。