A new method for testing pile by sin- gle-impact energy and P-S curve     

许昭永  段永康  王彬  胡毅力  杨润海  许峻  赵晋明 《地震学报(英文版)》2004,17(Z1)

Introduction Through many year's practices by vast numbers of scientific and technological workers andefforts from all aspects, the dynamic testing method of high-low strain has formally entered intothe technical code of foundation pile test of construction at last (The Industry Standards of thePeople's Republic of China, 2003). The striking mode of the dynamic testing method of high strainis stipulated as hammer in the code, the striking of rocket can also be used. The latter is widely…  相似文献   

珠江河口水环境时空变异对河口生态系统的影响   总被引：6，自引：0，他引：6       下载免费PDF全文

崔伟中 《水科学进展》2004,15(4):472-478

分析近20年来珠江河口水环境变异的特征,探讨珠江河口水环境与水生物相互联系和相互作用的关系。结果表明,珠江河口形态、地貌、水文情势和入河污染物等变异改变了珠江河口水生物的栖息条件,削弱了河口生态系统的自动调节修复能力和稳定性,对河口生态系统的物质循环、能量流动和发育演化平衡构成了重大影响。  相似文献   

红透山矿床变质岩系褶皱构造特征浅析   总被引：1，自引：0，他引：1  

王锡华  李伟 《矿产与地质》2004,18(3):245-248

红透山式铜-锌矿床形成于太古代克拉通裂谷槽盆中海底火山喷发-沉积环境。因此，矿床的空间展布严格受特定的含矿岩系所控制。槽盆构造中的岩层褶皱构造最发育，矿床赋存在具多期褶皱构造叠加的大型同倾向形褶皱内，褶皱的层间虚脱是控矿有利构造空间，可以借此预测矿体侧伏方向及赋存部位。  相似文献   

静止环境中有阻力圆盘浮力射流特性的研究——(II)流场特性分析          下载免费PDF全文

方神光  槐文信 《水科学进展》2004,(5)

在数值计算成果的基础上,对阻力圆盘浮力射流的流场进行了分析和总结,基于轴线流速的变化规律将盘后流场分为3个区域:回流区、过渡区和自相似区。得到了回流区的长度随弗劳德数F0、孔口直径D/d以及盘离孔口的距离H/d的变化规律,并得到了工况为H/D=1,D/d=2,6和H/D=3,D/d=2在不同弗劳德数F0条件下的横截面上的流速分布和达到自相似区的最小长度;结果表明弗劳德数F0的大小是决定绕流流态的主要因素;同时分析了由正常绕流发展到非正常绕流的压力场变化,发现由于弗劳德数F0的增大而导致流场中出现的第三个负压中心的大小和位置与绕流是否能正常发生存在密切的关系。  相似文献   

Impact of habitat heterogeneity on plant community pattern in Gurbantunggut Desert   总被引：5，自引：1，他引：5  

QIAN Yibing  WU Zhaoning  ZHANG Liyun  SHI Qingdong  JIANG Jin  TANG Lisong 《地理学报(英文版)》2004,14(4):447-455

1IntroductionStudy on the interrelationship between vegetation patterns and their habitat heterogeneity is important to recover and rehabilitate the desert vegetation, stabilize the desert ecosystem and prevent desert expansion. Domestic and foreign researchers have carried out many studies on this topic (Archer etal., 2002; Bolling etal., 2000; Chen etal., 2003; Dasti etal., 1994; Gu etal., 2002, Li etal., 2001; Li etal., 2001; Liang etal., 2003), which have used and refined statistic tech…  相似文献   

利用遥感综合分析西风引导气流与地形对沙尘运移路径的影响   总被引：2，自引：7，他引：2  

刘志丽  马建文  张仁健  王志刚  哈斯巴干  李启青 《中国沙漠》2004,24(3):330-334

沙尘暴的发生受大气环流、地表状况、降雨的影响，还受到局部地区地形的影响。一次规模较大的沙尘暴过程，沙尘可以从蒙古国和我国西部沙源地输送到我国东部、韩国、日本乃至夏威夷、美国西海岸。中日亚洲沙尘暴ADEC项目对亚洲沙尘暴的起沙、传输和降落的运行机制已经作了深入的研究，并建立了亚洲沙尘暴的数值模拟系统。本文以影响北京地区的沙尘暴事件为例，利用遥感技术，综合DEM地形数据和地面实测数据分析西风引导气流和地形对沙尘运移路径影响，将MODIs影像数据和DEM地形数据以及地面观测站点实测数据相结合，进行综合分析，结果表明在一次沙尘暴过程中，沙尘在运移过程中的运移路径明显地受到西风引导气流、沙尘粒子自然沉降规律以及局部地形的影响，要预防(减少)北京地区的沙尘暴仅仅作好北京地区的生态环境建设是不够的，加强北京周边地区，尤其是张家口地区、官厅水库库区及库区周围地区的生态环境建设尤为重要。  相似文献   

Assessing natural and cultural influence on soil in remnant tropical woodlands     

C Y Jim  Michael W H Chan 《Area》2004,36(1):6-18

Rural Hong Kong contains culturally protected enclaves of remnant woodlands that provide sanctuary for vegetation, wildlife and soil. This study focuses on the influence of natural and cultural factors on soil properties in woodlands with different human activities. At each of the nine selected sites, two pits were dug to collect soil samples for analysis of 24 physical and chemical properties. Analyses of variance between soil attributes and site factors suggest the prominence of woodland size, and important contribution of topography, aspect and parent material. Soil indicators of human impacts and the tenacity of woodland soil towards anthropogenic disturbance were demonstrated.  相似文献   

Hydro-geomorphic hazards and impact of man-made structures during the catastrophic flood of June 2000 in the Upper Guil catchment (Queyras, Southern French Alps)   总被引：2，自引：0，他引：2  

Gilles Arnaud-Fassetta  Etienne Cossart  Monique Fort 《Geomorphology》2005,66(1-4):41

The Guil River Valley (Queyras, Southern French Alps) is prone to catastrophic floods, as the long historical archives and Holocene sedimentary records demonstrate. In June 2000, the upper part of this valley was affected by a “30-year” recurrence interval (R.I.) flood. Although of lower magnitude and somewhat different nature from that of 1957 (>100-year R.I. flood), the 2000 event induced serious damage to infrastructure and buildings on the valley floor. Use of methods including high-resolution aerial photography, multi-date mapping, hydraulic calculations and field observations made possible the characterisation of the geomorphic impacts on the Guil River and its tributaries. The total rainfall (260 mm in four days) and maximum hourly intensity (17.3 mm h⁻¹), aggravated by pre-existing saturated soils, explain the immediate response of the fluvial system and the subsequent destabilisation of slopes. Abundant water and sediment supply (landsliding, bank erosion), particularly from small catchment basins cut into slaty, schist bedrock, resulted in destructive pulses of debris flow and hyperconcentrated flows. The specific stream power of the Guil and its tributaries was greater than the critical stream power, thus explaining the abundant sediment transport. The Guil discharge was estimated as 180 m³ s⁻¹ at Aiguilles, compared to the annual mean discharge of 6 m³ s⁻¹ and a June mean discharge of 18 m³ s⁻¹. The impacts on the Guil valley floor (flooding, aggradation, generalised bank erosion and changes in the river pattern) were widespread and locally influenced by variations in the floodplain slope and/or channel geometry. The stream partially reoccupied former channels abandoned or modified in their geometry by various structures built during the last four decades, as exemplified by the Aiguilles case study, where the worst damage took place. A comparative study of the geomorphic consequences of both the 1957 and 2000 floods shows that, despite their poor maintenance, the flood control structures built after the 1957 event were relatively efficient, in contrast to unprotected places. The comparison also demonstrates the role of land-use changes (conversion from traditional agro-pastoral life to a ski/hiking-based economy, construction of various structures) in reducing the Guil channel capacity and, more generally, in increasing the vulnerability of the human installations. The efficiency of the measures taken after the 2000 flood (narrowing and digging out of the channel) is also assessed. Final evaluation suggests that, in such high mountainous environments, there is a need to keep most of the 1957 flooded zone clear of buildings and other structures (aside from the existing villages and structures of particular economic interest), in order to enable the river to migrate freely and to adjust to exceptional hydro-geomorphic conditions without causing major damage.  相似文献   

An approach for quantifying geomorphological impacts for EIA of transportation infrastructures: a case study in northern Spain   总被引：2，自引：0，他引：2  

Jaime Bonachea  Viola Maria Bruschi  Juan Remondo  Alberto Gonzlez-Díez  Luis Salas  Jurjen Bertens  Antonio Cendrero  Csar Otero  Cecilia Giusti  Andrea Fabbri  Jos Ramn Gonzlez-Lastra  Jos María Aramburu 《Geomorphology》2005,66(1-4):95

A methodological proposal for the assessment of impacts due to linear infrastructures such as motorways, railways, etc. is presented. The approach proposed includes a series of specific issues to be addressed for each geomorphological feature analysed—both ‘static’ and ‘dynamic’—as well as a series of steps to be followed in the process.Geomorphic characteristics potentially affected were initially identified on the basis of a conceptual activities/impacts model that helps to single out geomorphic impacts related to environmental concerns for the area. The following issues were addressed for each individual impact: nature of potential effects; indicators that can be used to measure impacts; criteria of ‘geomorphologic performance’; procedure for measurement/prediction of changes; translation of geomorphologic impacts into significant terms from the viewpoint of human concerns; possible mitigation and/or compensation measures.The procedure has been applied to a case study corresponding to a new motorway in the Basque Country, northern Spain. Geomorphological impacts considered in this analysis included: (1) consumable resources; (2) sites of geomorphological interest; (3) land units with high potential for use, high productivity or value for conservation; (4) visual landscape; (5) slope instability processes. The procedure has been designed for implementation in a Geographic Information System (GIS) environment. Details are given on the application of the method to each individual impact analysed and results are presented in both numerical and map form.Impacts assessed were initially expressed by means of heterogeneous magnitudes, depending on the geomorphological feature considered. Those geomorphological impacts were then translated into significant terms and homogeneous magnitudes. Integration was carried out on the basis of impact values thus obtained. Final integrated results were also expressed in numerical and map form.The method proposed enables comparison of alternatives as well as ‘prediction’ and assessment of impacts in terms directly related to geomorphic characteristics. It also facilitates the expression of those impacts in terms that allow integration with other types of environmental impacts.  相似文献   

Testing the geomagnetic dipole hypothesis: palaeolatitudes sampled by large continents     

M. E. Evans 《Geophysical Journal International》2005,161(2):266-267

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