国家体育场柱脚锚固性能试验研究

大跨结构柱脚锚固性能是抗震设计的关键之一。国家体育场柱脚为钢柱脚,该钢柱脚锚固于钢筋混凝土承台中,其受力复杂,以往国内外类似的试验很少。笔者共进行了4个钢筋混凝土承台-钢柱脚试件锚固性能的试验研究,本文介绍其中2个几何尺寸较大的钢筋混凝土承台-钢柱脚试件锚固性能的试验研究概况,1个试件为混凝土承台中配置抗拔钢筋的试件,1个为混凝土承台中未配置抗拔钢筋的试件。通过单向重复加载下的钢柱脚锚固性能试验,对试件的锚固承载力、延性、合理配筋型式等进行了研究。试验结果表明,混凝土承台中配置抗拔钢筋的试件与未配置抗拔钢筋的试件相比其锚固承载力和延性显著提高。在试验基础上,建立了柱脚锚固承载力计算的桁架模型,计算结果与实测结果符合较好。     

云南易门狮子山落雪组凝灰质白云岩锆石U-Pb年代学研究及其地质意义

落雪组作为云南易门狮子山铜矿区最主要的赋矿层位，前人对该地层沉积时代研究程度较低，缺乏确切的地层形成时代资料。本文对狮子山铜矿区落雪组一段的凝灰质白云岩进行锆石U-Pb定年，获得3组有效²⁰⁷Pb/²⁰⁶Pb年龄值，分别为：①1.7 Ga—2.0 Ga；②2.11 Ga—2.43 Ga；③2.5 Ga—3.02 Ga。其中，第一组锆石年龄代表成岩期后构造热液事件；第二组锆石自形程度较好，棱角分明，发育韵律环带，为岩浆结晶锆石，其加权平均年龄为2299 Ma±29 Ma （n=27，MSWD=8.1），指示落雪组一段凝灰质白云岩的沉积时代为古元古代；第三组锆石年龄为捕获的古老继承锆石年龄，锆石的微量元素w（Y）—w（U）、w（Y）—w（Ce）/w（Ce）^*、w（Y）—w（Yb）/w（Sm）岩性判别图解显示，该组锆石主要来自陆壳花岗质岩石中的S型花岗岩，暗示扬子板块西南缘古元古代—新太古代存在近源出露的花岗岩类岩石，存在较早的酸性成分的大陆地壳。通过区域地层岩性特征和地层沉积时代对比分析，研究认为狮子山铜矿区出露的落雪组应为滇中易门群罗洼垤组的延伸，同属古元古代的沉积建造。     

Fabrics,facies control and diagenesis of lacustrine ooids and associated grains from the Upper Triassic,southwest England

Petrographic analysis of ooids from the Upper Triassic (Mercia Mudstone Group) of southwest England provides an opportunity to assess in detail the origins, transport pathways and diagenesis of an ancient oolite. The Clevedon Oolite is dolomitized and contains a variety of dissolved ooids (oomoulds) and associated grains. The oomoulds occur in well‐sorted, planar and cross‐stratified grainstones, packstones, sandstones and conglomerates associated with shoreface, intershoal, foreshore, beachrock and littoral strandplain deposits. The ooids grew in suspension in the shoreface zone and developed a radial aragonite microstructure. The ooids grew to 0.80 mm in diameter, after which they fractured or ceased growing. Broken grains deposited on or near mobile shoals were rapidly recoated, while other grains, deposited in less agitated, intershoal and lower foreshore areas, were micritized or microbially bound into grapestone aggregates. Locally peloids, intraclasts, quartz grains and micritized grains from intershoal areas supplied nuclei for ooids on nearby shoals. Grains deposited in foreshore areas were rapidly cemented into beachrock and reworked into conglomerates. Soon after deposition, the ooids were subjected to widespread aragonite dissolution followed by dolomitization. The lack of pre‐dolomitization calcite, together with the abundance of early (pre‐compaction) dolospar cements and fabric‐selective dolomitization of micritic fabrics, suggest aragonite dissolution by dolomitizing fluids. Copyright © 2002 John Wiley & Sons, Ltd.     

白云石重结晶作用及其地质意义

重结晶作用是白云石形成多期次动态系统中一种常见的成岩后生作用。白云石的成因问题，即“白云岩问题”一直困扰着地质学者，其中一个重要原因是白云岩中白云石的重结晶作用导致白云石形成的原始信息被掩盖，主要包括其结构和地球化学特征的变化。本文在调研国内外有关白云石重结晶作用文献基础上，系统梳理了地质历史时期古老地层中白云石和现代沉积白云石的重结晶作用，以及重结晶模拟实验中白云石岩石学及地球化学变化特征，阐述白云石重结晶的主要条件、影响因素及成岩过程中白云石重结晶作用发生的多期次性及主要变化特征，总结了白云石重结晶作用的研究意义，旨在为“白云岩问题”及成岩作用方面的研究提供一定的借鉴和启示。