地铁隧洞带水作业施工技术          下载免费PDF全文

罗启录 《探矿工程》2007,34(3):58-60

以在建的北京地铁十号线双井一劲松区间暗挖隧道为例，通过分析北京特殊地层在带水条件下单洞结构单线隧道台阶法的施工工艺，洞悉浅埋暗挖正台阶法施工中超前预加固、开挖时空顺序、台阶长度等工艺对围岩稳定性的影响程度。  相似文献   

Landscape governance: The “politics of scale” and the “natural” conditions of places     

Christoph Görg 《Geoforum》2007,38(5):954-966

Governance has become an iridescent concept in recent years. The term is widely used in almost all social-science disciplines as well as in the political process. The intention of this paper is not so much to clarify these sometimes vague meanings but to highlight some characteristics of environmental governance connected with the restructuring of the spatial dimensions of politics. It starts from the assumption that the quest for multi-level decision making is particularly pressing for environmental governance. However, multi-level governance raises concern about the constitution of various spatial levels and their relationships with each other, as discussed under the term of “politics of scale”. Moreover, it is argued that for environmental governance the spatial reference is strongly connected with another challenge, which concerns the question of how to deal with the biophysical conditions of particular places. The term landscape governance is introduced to tackle this question without referring to an ontologically given space. Thus, landscape governance deals with the interconnections between socially constructed spaces (the politics of scale) and “natural” conditions of places. For this task, the concept of societal relationships with nature is introduced and applied to the term “landscape” as a bridging concept between social and natural sciences. The paper illustrates the approach of landscape governance with examples of problem-oriented interdisciplinary research at the UFZ-Centre for Environmental research in Leipzig, Germany.  相似文献   

液体闪烁计数技术测氡在铀矿勘查中的应用研究     

邓小卫  王国庆  李洪璧  蔺志璧  贺建国 《铀矿地质》2007,23(1):43-48

在火山岩、花岗岩地区和中新生代盆地铀矿勘查中进行了大量的液体闪烁测氡工作，发现该方法探测效率高、抗干扰能力强、重复性好、异常清晰，取得了较好的地质找矿效果，证实了该方法的有效性和可行性。  相似文献   

Residual strength of slip zones of large landslides in the Three Gorges area, China   总被引：2，自引：0，他引：2  

B.P. Wen  A. Aydin  N.S. Duzgoren-Aydin  Y.R. Li  H.Y. Chen  S.D. Xiao 《Engineering Geology》2007,93(3-4):82-98

Slip zones of the large landslides in the Three Gorges area are commonly composed of fine-grained soils with substantial amount of coarse-grained particles, particularly gravel-sized particles. In this study, residual strength of the soils from slip zones of these landslides were examined in relation to their index properties based on a survey of 170 landslides. It was found that laboratory-determined residual friction angle using gravel-free fraction of the disturbed soils from the slip zones was closely related to clay content, liquid limit and plasticity index. On the other hand, in-situ residual friction angle of these soils (i.e. including gravel fraction) showed very weak correlations with clay content and Atterberg limits, but was largely dependent on gravel and fines (clays + silts) contents, increasing with gravels and decreasing with fines, and displayed strong linear correlation with the ratio of gravel to fines contents. These observations indicate that among the index properties, clay content and Atterberg limits can be used to estimate residual strength of the soils finer than 2 mm, but they are not appropriate evaluate the residual strength of the soils containing considerable amount of gravel-sized particles. For the latter, particle size distribution (particularly the ratio of gravel to fines contents) appears to be a useful index. Additionally, it was found that there was no identifiable correlation between relative abundance of individual major clay minerals and residual friction angles of both gravel-free fraction of disturbed and in-situ soils, suggesting that influence of clay minerals on residual strength of these soils can not be simply evaluated based on their abundance.  相似文献   

大底盘多塔楼结构的混合隔震控制   总被引：2，自引：0，他引：2  

谭平  周云  周福霖 《世界地震工程》2007,23(2):12-19

结合某实际工程,针对大底盘多塔楼结构提出混合隔震的控制策略,即对大底盘上的一栋或多栋塔楼采用隔震技术,并在隔震层附设一定数量的被动、主动或半主动的减震控制装置。建立了这种大底盘多塔楼结构混合隔震控制体系的运动方程,方程中各塔楼与下部结构及隔震层之间的刚度解耦,并考虑了隔震层的非线性。研究中比较了被动非线性粘滞阻尼器,半主动变孔隙阻尼器与理想主动控制时的减震控制效果。结果表明,这种混合隔震体系可以有效地减小上部塔楼与下部结构的地震反应,提高大底盘多塔楼结构的抗震安全性,取得明显的经济和社会效益。半主动变孔隙阻尼器可以极好地追踪理想主动控制力,取得与理想主动控制相近的减震控制效果。被动非线性粘滞阻尼器也能取得较好的减震效果,且易于维护,经济性较好,从工程应用的角度来看更为现实可行,具有较好的应用推广价值。  相似文献   

改良FS-3D-TrueFISP序列与传统序列在软骨成像中的对比研究     

岳云龙  韩鸿宾 《CT理论与应用研究》2007,16(2):80-85

目的:总结正常软骨在改良脂肪抑制三维真实稳态自由进动序列上的表现,与传统序列对比研究软骨显像的图像质量,探讨经过改良以后的脂肪抑制三维真实稳态自由进动序列应用于软骨成像的可行性.方法:应用脂肪抑制三维快速小角度激发序列、三维双回波稳态序列、脂肪抑制快速自旋回波质子密度加权序列,以及经过改良以后的两个脂肪抑制三维真实稳态自由进动序列,对10名志愿者的膝关节进行扫描.测量各序列软骨及关节滑液的信号强度及背景噪声,计算各种方法所得图像的关节软骨的信噪比、关节软骨与滑液的对比噪声比及对比噪声比效率,比较各序列所得的信噪比、对比噪声比及对比噪声比效率之间有无统计学差异.结果:在改良的序列上软骨信号强度介于关节液与邻近骨质之间.6例信号均匀,4例软骨信号可见与脂肪抑制三维快速小角度激发序列相似的分层现象,各序列的信噪比、对比噪声比及对比噪声比效率差异具有显著性.采集次数为2次的脂肪抑制三维真实稳态自由进动序列的对比噪声比及对比噪声比效率优于其他序列.结论:经过改良后的真实稳态自由进动序列可以在保持关节软骨一定的信噪比的前提下在短时间内获得与关节滑液之间具有良好对比噪声比的图像.真实稳态自由进动序列可以用于关节软骨病变的诊断.  相似文献   

以海原断裂甘肃老虎山段为例浅析走滑断裂古地震记录的完整性——兼论古地震研究中的若干问题     

刘静徐锡伟  李岩峰冉勇康 《地质通报》2007,26(6):50-660

在简单介绍海原断裂老虎山段松山探槽点古地震工作的基础上,分析了制约走滑断裂上古地震记录完整性的因素。松山探槽点跨断裂开挖的2个探槽揭示颜色和粒度不同的地层互层的沉积序列呈近水平面状展布。在断裂带内地层发生错断、旋转和拖曳等变形现象。多个层位上的这种变形表明该点揭示了6次古地震事件。炭屑的~(14)C年龄限定了6次事件均发生在距今3500～3900年以来,其中最新的4次事件从老到新分别为0～410aAD、890～1000年之后不久、1440～1640 aAD和1990年景泰-天祝Mw5.8级历史地震。该序列及其他例子表明连续的、高沉积速率的微构造环境是走滑断裂上探槽选取的重要原则。  相似文献   

圆形断面管道非满流流速计算表达式   总被引：1，自引：0，他引：1       下载免费PDF全文

茅泽育  赵璇  罗昇 《水科学进展》2007,18(2):170-174

工程实际中,常需要计算某一充满度下管道非满流的流量及流速。目前大多数计算模型均采用水力半径作为反映过流断面形状及几何尺寸的特征参数。针对不同充满度的研究结果表明,这种类型模型的计算结果与真实的流动特性并不相符,尤其当水深接近管顶时。根据水动力学基本原理及试验研究手段,对圆形断面管道无压均匀流流量-充满度非单一性进行了探索,并提出了以流量作为形状特征参数的更为合理且简单实用的水流流速计算表达式。  相似文献   

大试管回流消解-等离子体发射光谱／质谱法测定植物样品中多元素   总被引：2，自引：1，他引：2  

马生凤温宏利  巩爱华孙德忠 《岩矿测试》2007,26(3):183-187

采用大试管和红外加热的多孔控温消解炉的简单装置消解植物样品，电感耦合等离子体发射光谱／质谱法测定其中的主量和痕量元素，对消解温度、消解时间、消解溶剂、样品取样量等条件进行考察。用植物国家一级标准物质进行前处理及测定，验证方法的可行性，测定值与标准值基本吻合。方法不仅能同时测定B、Ba、Ca、Cd、Cu、K、Mg、Mn、Na、Ni、P、S、Zn、CoSr、Pb、Cr等元素，还适用于Hg、As挥发性元素的消解测定。方法的精密度（RSD，n=10）≤10％。  相似文献   

南方集约农区农牧结合对农业可持续发展的作用   总被引：8，自引：0，他引：8  

张卫建  谭淑豪  冯金侠  章熙谷 《地域研究与开发》1998,17(2):24-27

为寻求该区农业可持续发展的途径,作者在分析其农业可持续发展的主要制约因素基础上,对农牧结合在实现农业可持续发展中的功能作了全面论述。结果表明,农牧结合是实现该区农业可持续发展的一条有效途径。最后还提出了该农区农牧结合的可行途径及有效措施  相似文献