Centrifuge modelling-based verification of response spectra design methods for some vulnerable structures

Residential RC framed structures suffered heavily during the 2001 Bhuj earthquake in Gujarat, India. These types of structures also saw severe damage in other earthquakes such as the 1999 Kocaeli earthquake in Turkey and 921 Ji-Ji earthquake in Taiwan. In this paper the seismic response of residential structures was investigated using physical modelling. Idealised soft storey and top heavy, two degrees of freedom (2DOF) portal frame structures were developed and tested on saturated and dry sand models at 25 g using the Schofield Centre 10-m Beam Centrifuge. It was possible to recreate observed field behaviour using these models. As observed in many of the recent earthquakes, soft storey structures were found to be particularly vulnerable to seismic loads. Elastic response spectra methods are often used in the design of simple portal frame structures. The seismic risk of these structures can be significantly increased due to modifications such as removal of a column or addition of heavy water tanks on the roof. The experimental data from the dynamic centrifuge tests on such soft storey or top-heavy models was used to evaluate the predictions obtained from the response spectra. Response spectra were able to predict seismic response during small to moderate intensity earthquakes, but became inaccurate during strong earthquakes and when soil structure interaction effects became important. Re-evaluation of seismic risk of such modified structures is required and time domain analyses suggested by building codes such as IBC, UBC or NEHRP may be more appropriate.     

等截面单桩抗拔承载性状试验研究

在基坑中对等截面单桩进行了抗拔静载试验，在桩身设置应变式钢筋计，成功测得桩身各截面的应变数据。分析试验所得数据，对试验抗拔桩抗拔系数的取值、侧摩阻力的发挥、混凝土桩身的开裂等进行了探讨，相应给出了抗拔桩的设计建议。     

陕西小秦岭金矿床“三位一体”勘查区找矿预测地质模型及找矿意义

为解决制约找矿突破的关键问题,运用勘查区找矿预测理论,通过开展构造-蚀变专项填图、典型矿床解剖等工作,重点研究了小秦岭金矿田石英脉型金矿床的成矿地质体、成矿构造和成矿结构面、成矿作用的特征标志;在综合分析研究的基础上初步构建了"三位一体"找矿预测模型;并结合岩石地球化学测量成果,圈定了13处找矿靶区,其中两处找矿靶区经工程验证见到工业矿体,初步证明陕西小秦岭金矿田石英脉型金矿床"三位一体"勘查区找矿预测地质模型预测效果良好,在矿田新一轮"攻深找盲"工作中具有现实的指导意义。      

大兴安岭扎兰屯地区晚奥陶世石英闪长岩体岩石地球化学特征及其地质意义

扎兰屯音河岩体被音河水系分为南、北两部分,研究发现南、北岩体形成年代不同,选取南部岩体(称为二村岩体)进行研究。二村岩体主要由石英闪长岩-英云闪长岩组成,石英闪长岩的LA-ICP-MS锆石U-Pb年龄为444.0±4.6Ma,时代为晚奥陶世。岩石化学组成相对富钠、贫钾,Na2O/K2O值大于1(1.73~3.17),属中钾钙碱性系列。岩石富含轻稀土元素、亏损重稀土元素,富集大离子亲石元素Rb、Ba、K,显著亏损Nb、Ta、P、Ti等高场强元素。矿物组成及岩石地球化学特征指示其为I型花岗岩。岩体的形成时代、构造背景与多宝山岛弧火成岩相似,为区域多宝山岛弧西南向延伸提供了新的制约。     

硫酸盐渍土含水率单次递减条件下的盐胀特性

为探究硫酸盐渍土在含水率递减下的盐胀特性,通过自主设计的试验装置,在室内开展了11组含水率单次递减下的盐胀试验,共历时2 868 h。结果表明：在含水率单次递减下硫酸盐渍土的起胀含盐量约为1.2%。含盐量<1.2%时,土体干缩,干缩量与含盐量近似呈下凸的二次抛物线规律,且干缩峰值含盐量约为0.5%;含盐量≥1.2%时,土体膨胀,且盐胀率与含盐量近似呈线性增大规律。盐胀敏感含水率区间受含盐量影响很小,含盐量从1.5%增至4.0%,盐胀敏感含水率区间基本稳定。此外,含水率递减速率与含盐量呈负相关规律,同一含盐量的硫酸盐渍土,其含水率的递减速率随含水率的降低亦减慢。基于以上试验结果,进一步开展了4组单次降温下的盐胀对比试验,结果表明：含盐量升高时,起胀温度区间逐渐升高,盐胀敏感温度区间的区间范围逐渐扩大。单次降温下的盐胀率均高于含水率单次递减下的盐胀率,且随着含盐量的升高两试验条件下的盐胀率差值趋于一常数。研究结果对西北地区高含盐量的残余型硫酸盐渍土地基的盐胀性评价具有重要指导意义。     

耐高温高压复合保温管研究

耐高温高压复合保温管主要解决超高温高压环境下钻孔测量问题。为攻克超高温高压环境下真空绝热保温、高压密封等关键技术,研究的耐高温高压复合保温管为“超高温钻孔测量仪”提供一种耐高温承压管,使用环境温度可达270 ℃,压力120 MPa。通过室内测试与现场应用,说明其满足超高温高压要求,可应用于高温地热能钻探工程、干热岩钻探工程、科学钻探工程、深部矿产资源勘探和深部油气资源勘探等工程中,为超高温大深度钻井测量提供技术支撑。     

坑式钢管静压桩在地基加固中的应用

坑式钢管静压桩是解决既有建筑物因软弱土层地基产生沉降变形的一种技术方法。针对山西北化关铝化工有限公司质检楼地基沉降变形及工程地质条件,提出了采用坑式钢管静压桩进行加固处理的设计方案,介绍了坑式钢管静压桩施工方案和施工流程及注意事项;总结了施工过程中遇到的问题,并对施工后的监测数据进行了分析。结果表明,坑式钢管静压桩施工对软弱地基加固效果良好,可成功地解决软弱土层产生的地基沉降开裂问题。     

柴达木盆地西北缘石英闪长岩的形成时代、岩石成因及地质意义

柴达木盆地西北缘石英闪长岩Al2O3含量较高,全碱(Alk)含量较低,Na2OK2O,铝饱和指数A/CNK为0.87~0.91,属钙碱性准铝质岩石系列。球粒陨石标准化的稀土元素配分曲线表现为轻稀土元素富集型,轻、重稀土元素分馏明显,Eu弱负异常;微量元素地球化学特征显示,岩石富集Rb、Th、U等大离子亲石元素,亏损Nb、Ta、P、Ti等高场强元素,Nb/La和Rb/Nb比值较低,具有I型花岗岩的特征。石英闪长岩Ca O/Na2O比值较高(2.32~2.64),结合源岩判别图解综合推断其源于变玄武岩的部分熔融。全岩Zr饱和温度计算结果显示初始岩浆温度768℃;岩石地球化学特征表明岩浆源区压力1.5 Ga,源岩部分熔融的残留相可能为石榴子石+角闪石+金红石。经过锆石阴极发光分析和MC-LA-ICP-MS锆石U-Pb测年,获得206Pb/238Pb加权平均年龄为252±1 Ma,代表了柴达木盆地西北缘石英闪长岩的成岩年龄。结合区域地质演化特征,认为该岩体形成于与板块俯冲有关的火山弧构造环境,是晚二叠世末期宗务隆洋壳向柴北缘欧龙布鲁克地块俯冲,变玄武岩在相对较高的温压条件下发生部分熔融形成的。     

Geochemical and electron paramagnetic characteristics of quartz from a multi-stage vein environment, Cowarra gold deposit, New South Wales

The characterisation of quartz using trace element geochemistry and electron paramagnetic resonance measurements has been tested for different generations of quartz veining in the multi-stage hydrothermal vein system at Cowarra. Quartz closely associated with gold mineralisation can be distinguished from earlier and later quartz generations in the mineralised environment, and both types can be distinguished from regional, barren quartz veins. These separate stages of quartz veins are also recognised from their fluid inclusion characteristics. Geochemical differences in the quartz partly reflect the presence of minor mineral inclusions, particularly sulfides and arsenopyrite.The study highlights the importance of understanding the paragenetic sequence of quartz vein development in a mineralised environment and the need for careful, thorough sampling before attempting geochemical and EPR characterisation of quartz as an exploration technique.     

水文水井抽水试验参数自动监测系统硬件设计

设计了以单片机为核心的抽水试验参数自动监测系统，能自动完成水位、出水量、地下水温和承压水水头高度等主要参数的自动监测，并现场打印数据；能和PC机进行数据通讯，转储数据，通过PC机进行进一步数据处理，输出打印S＝f(t)和Q＝f(t)曲线，建立数据库。