北京市地铁暗挖施工沉降控制探讨   总被引：1，自引：0，他引：1  

焦猛 《北京测绘》2008,(3):67-71

仅以北京市地铁4#线张自忠车站主体暗挖施工的沉降监控项目为研究背景,对穿越城市主干道的车站结构暗挖施工进行连续性的沉降变形监测;从地下构筑物暗挖施工的工序变化与地表沉降的关系进行试验研究.在预测基础上对获取的数据进行多层次的统计与分析,以研究其变形规律与稳定性,实现了信息化施工.  相似文献   

黑河中下游荒漠区植物多样性分布对土壤水分变化的响应   总被引：9，自引：0，他引：9  

李新荣  何明珠  贾荣亮 《地球科学进展》2008,23(7):685-691

基于对黑河流域中下游荒漠区植被和土壤生境的调查分析,以土壤水分在各调查样地中的差异来反映研究区的生态水文特征,采用种的丰富度和多度来代表荒漠植物多样性研究了荒漠植物,包括隐花植物多样性分布对土壤水分变化的响应。土壤水分变化不仅直接影响着荒漠植物的多样性,而通过影响其它生境因子又间接地影响着多样性的维持。因此,如何维持中下游相对稳定的土壤水分来源是该区荒漠植物多样性保育今后所要面临的挑战。  相似文献   

黑河流域水环境演变及其驱动机制研究进展   总被引：10，自引：0，他引：10  

肖生春  肖洪浪 《地球科学进展》2008,23(7):748-755

基于近几十年来诸多学者对西北干旱区典型内陆河流域——黑河流域水环境演变诸方面研究成果,综述了上游山区成水环境、中游绿洲用水环境和下游荒漠天然绿洲水成环境在不同时间尺度上的演变过程及其驱动机制。通过对各种古环境代用指标的对比研究表明：在大尺度上,流域上下游表现出阶段性的一致性水环境演变趋势;在小尺度上,则表现水环境演变的时空异质性。驱动机制方面,在空间上,流域上、中、下游水环境演变的气候变化和人类活动影响驱动作用各有侧重;在时间上,表现为不同尺度上气候变化与流域人类活动耦合作用的驱动机制。  相似文献   

全程注浆在隧道穿越既有建筑物中的试验研究   总被引：6，自引：0，他引：6  

逢铁铮 《岩土力学》2008,29(12):3451-3458

厦门市成功大道工程是福建省2005年重点建设项目,项目由多座立交和两条特长城市隧道组成,其中莲前至梧村山隧道里程长度为3 700 m,采用双洞双向6车道标准.隧道在埔南工业区的685 m段采用跨度达34 m的浅埋连拱结构穿越地面67栋密集建构筑物.洞项至地表的覆盖层只有7～24 m,水文、地质较差,洞顶基本为杂填土和残积亚黏土层,洞底多为全、强风化花岗岩,地下饱和水位高(局部洞身地处海平面以下20 m左右),施工风险极大.为了保证既有地面建构筑物的安全,提出了以过程控制和过程恢复为核心的全过程注浆方案,并预留104#和105#拆迁房为试验楼,采取地面注浆和洞内注浆的方法来进行过程控制和房屋抬升的试验.在现场试验中,根据全过程注浆的思路,提出了建筑物安全风险控制标准.通过室内试验比较了不同浆液的注浆效果,分析实际施工中房屋摹础改造和地基注浆加固、动态跟踪注浆以及工后房屋恢复抬升的特点和效果.在注浆过程中进行实时的信息反馈和分析,进而了解注浆工艺和参数与地层加崮效果和建筑物抬升效果之间的关系,得出了一系列有意义的结论.试验结果为隧道后续穿越建构筑物施工提供经验和指导,研究思路可为类似的隧道穿越工程提供一定的参考.  相似文献   

The characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin   总被引：2，自引：2，他引：0  

Xianqing Li  Guoyi Hu  Jian Li  Dujie Hou  Peng Dong  Zhihong Song  Yunfeng Yang 《中国地球化学学报》2008,27(2):109-120

The Central Gas Field is a famous large-sized gas field in the Ordos Basin of China. However, identification of main gas sources of the Ordovician reservoirs in this gas field remains puzzling. On the basis of a lot of geochemical data and geological research on natural gases, the characteristics and sources of natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin were studied. The results indicated that natural gases from Ordovician weathered crust reservoirs in the Central Gas Field in the Ordos Basin have similar chemical and isotopic compositions to highly mature and over-mature dry gases. Both coal-derived gases and oil-type gases coexist in the Central Gas Field in the Ordos Basin. The former was derived mainly from Carboniferous-Permian coal measures and the latter from Lower Paleozoic marine carbonates. It is suggested that coal-derived gases occur in the eastern part of the Central Gas Field while oil-type gases may be produced mainly in the northern, western and southern parts of the Central Gas Field in the Ordos Basin.  相似文献   

Mesoproterozoic Continental Arc Type Granite in the Central Tianshan Mountains: Zircon SHRIMP U-Pb Dating and Geochemical Analyses     

YANG Tiannan  LI Jinyi  SUN Guihu  WANG Yanbin 《《地质学报》英文版》2008,82(1):117-125

The Central Tianshan belt in northwestern China is a small Precambrian block located in the southern part of the Central Asia Orogenic Belt （CAOB）, which is considered as ＂the most voluminous block of young continental crust in the world＂ that comprises numerous small continental blocks separated by Paleozoic magmatic arcs. The Precambrian basement of the central Tianshan Mountains is composed of volcanic rocks and associated volcano-sedimentary rocks that were intruded by granitic plutons. Geochemical analyses demonstrate that the granitic plutons and volcanic rocks were generated in the Andean-type active continental arc environment like today＇s Chile, and the zircon U-Pb SHRIMP dating indicates that they were developed at about 956 Ma, possibly corresponding to the subduction of the inferred Mozambique Ocean under the Baltic-African super-continent.  相似文献   

Isotopes and Geochronology of the Meixian-type Pb-Zn-(Ag)Deposits,Central Fujian Rift,South China:Implications for Geological Events     

FENG Chengyou  ZHANG Dequan  LI Daxin  SHE Hongquan  DONG Yingjun 《《地质学报》英文版》2008,82(4):826-837

Central Fujian Rift is another new and important volcanogenic massive sulfide Pb-Zn polymetallic metallogenetic belt. In order to find out the material genesis and mineralization period of Meixian-type Pb-Zn-Ag deposits, S and Pb isotope analysis and isotope geochronology of ores and wall rocks for five major deposits are discussed. It is concluded that the composition of sulfur isotope from sulfide ore vary slightly in different deposits and the mean value is close to zero with the 834S ranging from -3.5‰ to ＋5.6‰ averaging at ＋2.0‰, which indicates that the sulfur might originate from magma or possibly erupted directly from volcano or was leached from ore-hosted volcanic rock. The lead from ores in most deposits displays radioactive genesis character （206pb/204pb〉18.140, 207Pb/204pb〉15.584, 208pb/204pb〉38.569） and lead isotope values of ores are higher than those of wall rocks, which indicates that the lead was likely leached from the ore-hosted volcanic rocks. Based on isotope data, two significant Pb-Zn metallogenesis are delineated, which are Mid- and Late-Proterozoic sedimentary exhalative metailogenesis （The single zircon U-Pb, Sm-Nd isochronal and Ar-Ar dating ages of ore- hosted wall rocks are calculated to be among 933-1788 Ma.） and Yanshanian magmatic hydrothermal superimposed and alternated metallogenesis （intrusive SHRIMP zircon U-Pb and Rb-Sr isochronal ages between 127-154 Ma）.  相似文献   

Late Cenozoic Stratigraphy and Paleomagnetic Chronology of the Zanda Basin, Tibet, and Records of the Uplift of the Qinghai-Tibet Plateau   总被引：1，自引：0，他引：1  

MENG Xiangang  ZHU Dagang  SHAO Zhaogang  YANG Chaobin  HAN Jianen  YU Ji  MENG Qingwei  LU Rongping 《《地质学报》英文版》2008,82(1):63-72

The characteristics of Late Cenozoic tectonic uplift of the southern margin of the Qinghai- Tibet Plateau may be inferred from fluvio-lacustrine strata in the Zanda basin, Ngari, Tibet. Magnetostratigraphic study shows that the very thick fluvio-lacustrine strata in the basin are 5.89- 0.78 Ma old and that their deposition persisted for 5.11 Ma, i.e. starting at the end of the Miocene and ending at the end of the early Pleistocene, with the Quaternary glacial stage starting in the area no later than 1.58 Ma. Analysis of the sedimentary environment indicates that the Zanda basin on the southern Qinghai-Tibet Plateau began uplift at -5.89 Ma, later than the northern Qinghai-Tibet Plateau. Presence of gravel beds in the Guge and Qangze Formations reflects that strong uplift took place at -5.15 and -2.71 Ma, with the uplift peaking at -2.71 Ma.  相似文献   

松辽平原区荒漠化形成与发展的地质基础   总被引：1，自引：0，他引：1  

赵福岳  路云阁  姜德仁  陈树旺  姜琦刚 《国土资源遥感》2008,19(3):90-93

利用卫星数据,结合实地地质调查、光释光（Optically Stimulated Luminecence, OSL）测年及孢粉数据,从地层、新构造和沉积环境等角度阐述了松辽平原晚更新世晚期湖积环境的形成与变化,提出了松辽平原晚更新世晚期湖积环境或湖积物质是区内荒漠化形成与发展的地质基础。  相似文献   

框架预应力锚杆边坡支护结构的稳定性分析方法及其 应用   总被引：4，自引：0，他引：4  

周勇  朱彦鹏 《工程地质学报》2008,16(3):376-382

以边坡极限平衡理论及框架预应力锚杆边坡支护结构的圆弧滑动破坏模式为基础,在考虑框架、锚杆对土体边坡稳定性影响的情况下,基于圆弧滑动条分法的思想利用积分法建立了内部稳定性安全系数计算模型和最危险滑移面搜索模型。确定滑移面圆心坐标为几何控制参数,推导了安全系数计算模型中各变量与滑移面圆心坐标之间的函数关系式,从而获得了滑移面几何控制参数与内部稳定性安全系数之间的函数关系。利用网格法对框架预应力锚杆支护结构最危险滑移面的圆心坐标进行动态搜索和求解。最后采用Matlab语言编制了框架预应力锚杆边坡支护结构的稳定性分析程序,并结合工程实例进行了验算,讨论了此种方法的适用条件,结果表明该方法简明适用,较传统的经验分析方法更加合理。  相似文献