地铁隧道开挖引起地表塌陷分析   总被引：6，自引：1，他引：6  

黄俊  张顶立  虞辰杰 《中国地质灾害与防治学报》2004,15(1):65-69

深圳富水软弱地层地铁隧道开挖中出现的工作面失稳及由此引起的地表塌陷是地铁安全施工中极其重要的方面，对施工安全、进度都有较大影响，同时也对整个工程造成巨大的经济损失。通过对深圳地铁Ⅰ期工程土建施工中全线部分暗挖标段出现的工作面失稳、地表塌陷工程实践和现场监测结果分析，特别着重对连续2次出现地表塌陷的3A标暗挖隧道研究，从隧道上覆地层物理力学性质参数、地层变形监测分析及施工工艺原因3方面阐述了地表塌陷的原因。明确提出剪切破坏线和失水空洞区的概念，确定出引发地表塌陷的主导因素为施工工艺原因。建议针对该类地层条件，应做好超前地质预报．适当调整预加固参数．加强隧道结构和地表的动态变形监测，施工技术人员做到准确了解施工现场动态，及时调整施工工艺参数，以保证隧道的安全施工。分析结果对深圳地铁Ⅱ期工程施工及类似地层条件地下工程施工提供科学预测、预防地表塌陷的方法和技术措施，达到地铁隧道施工中经济效益与安全施工的统一。  相似文献   

信号传输的屏蔽措施与研究     

薄永进 《云南地理环境研究》2004,(Z1)

为了保证信息的正常传输,当布线环境有电磁干扰时,要相应地采用屏蔽系统。为了保证电子设备的正常工作,采用适当的屏蔽措施来阻挡或衰减电磁干扰。本文阐述了在现阶段雷灾中屏蔽的重要性以及屏蔽的具体施工,并对屏蔽的检验提出了一定的见解。  相似文献   

基于等高线的DEM生成算法研究和实现   总被引：5，自引：0，他引：5  

刘锦中  马辉 《现代测绘》2004,27(3):34-35,48

数字高程模型是近年来发展起来的为地理信息系统提供空间分析和辅助决策的数据基础。随着科学技术特别是计算机技术的迅速发展，DEM在数据获取方法、数据存储和数据处理速度等方面已经取得突破性进展。通过系统介绍生成DTM过程中等高线的离散化方法，DELAUNAY三角网的特性和基于等高线数据的TIN的建立，以及对产生的问题的一些解决方法。  相似文献   

基于物方影像匹配和概率松弛的断面自动提取   总被引：4，自引：0，他引：4  

郑顺义  张祖勋  张剑清 《测绘信息与工程》2004,29(2):26-27

提出了基于物方影像匹配的断面提取,为了提高匹配的可靠性,引入了概率松弛法,最终获得了高精度的断面.  相似文献   

视频对象分割及跟踪方法研究     

沈未名  江柳  种衍文 《武汉大学学报(信息科学版)》2004,29(3):274-277

讨论和分析了视频对象全自动提取及后续帧中的跟踪过程及采用的方法 ,对其算法、分割性能和结果进行了比较和评述。并结合Hausdorff和Snake跟踪器 ,对初始对象轮廓进行跟踪。结果证明 ,这种跟踪方法能有效地解决对象被遮挡和形变以及背景移动的问题  相似文献   

等高线拓扑关系的构建以及应用   总被引：9，自引：1，他引：9  

王涛  毋河海 《武汉大学学报(信息科学版)》2004,29(5):438-442

提出了等高线拓扑关系的描述框架 ,其规范化描述形式具有更强的适用性 ,使用三角网作为工具设计了建立拓扑关系的算法。以提出的拓扑关系描述为基础 ,具体实现了等高线高程自动赋值 ,处理过程可以同时考虑开曲线 (包括断线 )和闭曲线 ,提高了可靠性和自动化程度 ,并进一步将断线连接为完整目标 ,减少了人机交互的编辑工作  相似文献   

Fractionation mechanism of stable isotope in evaporating water body     

ZHANG Xinping  TIAN Lide  LIU Jingmiao 《地理学报》2005,15(3):375-384

Under Rayleigh equilibrium condition, stable isotopic ratio in residual water increases with the decrease of the residual water proportion f exponentially, and the fractionation rate of stable isotopes is inversely proportional to temperature. However, under kinetic evaporation condition, the fractionation of stable isotopes is not only related to the phase temperature but also influenced by the atmospheric humidity and the mass exchange between liquid and vapor phases. The ratio δ in residual water will not change with f after undergoing evaporation of a long time for great relative humidity. The rate that the evaporating water body reaches isotopic steady state is mainly dependent on the relative humidity in atmosphere. The analysis shows that the actual mean linear variety rates, about -30.0, of the δ18O in residual water versus the residual water proportion at Nagqu and Amdo stations are consistent with the simulated process under temperature of 20 oC and relative humidity of 50%. The distillation line simulated under Rayleigh equilibrium condition is analogous to the global meteoric water line (MWL) as the temperature is about 20 oC. Under non-equilibrium condition, the slope and constant values of distillation line are directly proportional to temperature and relative humidity. According to the basic data, the simulated distillation line is very consistent with the actual distillation line of Qinghai Lake.  相似文献   

青藏高原腹地植物碳同位素组成对环境条件的响应   总被引：7，自引：0，他引：7  

王谋  李勇  黄润秋  李亚林  张玉修 《山地学报》2005,23(3):274-279

现代植物碳同位素组成是特定环境影响的结果,通过对植物碳同位素组成的研究可以揭示植物生长期环境信息。针对青藏高原腹地高寒草甸~高寒草原过渡区植被碳同位素组成进行研究;该区高山嵩草样δ13C值在-25.63‰~-27.95‰间,平均值-26.63‰;高寒草原区混合样δ13C值于-26.29‰~-27.73‰间,平均值-27.04‰。高山嵩草样δ13C值总体呈现由南东往北西方向正偏趋势,研究区北部高寒草原区混合植物样也呈现出由南向北富重碳同位素趋势。这些变化规律被认为是主要受降水环境影响的结果,而区域内降水条件的展布规律则是受高原夏季风运移方式的控制。对植物δ13C值与地理位置的回归分析表明,该区植被碳同位素组成与地理位置相关,高山嵩草样(r=0.44603,n=29,p<0.05)和混合样(r=0.8112,n=5,p<0.1)均表现出对区域降水环境条件的良好响应。据此,以该区植物δ13C值为背景,进行合理推算,拟定了研究区内干旱区和湿润区界限的位置。  相似文献   

Intensification of Southern Hemisphere westerly winds 2000–1000 years ago: evidence from the subantarctic Campbell and Auckland Islands (52–50°S)          下载免费PDF全文

Chris S. M. Turney  Matt McGlone  Jonathan Palmer  Christopher Fogwill  Alan Hogg  Zoë A. Thomas  Mathew Lipson  Janet M. Wilmshurst  Pavla Fenwick  Richard T. Jones  Ben Hines  Graeme F. Clark 《第四纪科学杂志》2016,31(1):12-19

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Characterizing spatial and temporal variation in 18O and 2H content of New Zealand river water for better understanding of hydrologic processes     

Jing Yang  Bruce D. Dudley  Kelsey Montgomery  Will Hodgetts 《水文研究》2020,34(26):5474-5488

Time series of hydrogen and oxygen stable isotope ratios (δ²H and δ¹⁸O) in rivers can be used to quantify groundwater contributions to streamflow, and timescales of catchment storage. However, these isotope hydrology techniques rely on distinct spatial or temporal patterns of δ²H and δ¹⁸O within the hydrologic cycle. In New Zealand, lack of understanding of spatial and temporal patterns of δ²H and δ¹⁸O of river water hinders development of regional and national-scale hydrological models. We measured δ²H and δ¹⁸O monthly, together with river flow rates at 58 locations across New Zealand over a two-year period. Results show: (a) general patterns of decreasing δ²H and δ¹⁸O with increasing latitude were altered by New Zealand's major mountain ranges; δ²H and δ¹⁸O were distinctly lower in rivers fed from higher elevation catchments, and in eastern rain-shadow areas of both islands; (b) river water δ²H and δ¹⁸O values were partly controlled by local catchment characteristics (catchment slope, PET, catchment elevation, and upstream lake area) that influence evaporation processes; (c) regional differences in evaporation caused the slope of the river water line (i.e., the relationship between δ²H and δ¹⁸O in river water) for the (warmer) North Island to be lower than that of the (cooler, mountain-dominated) South Island; (d) δ²H seasonal offsets (i.e., the difference between seasonal peak and mean values) for individual sites ranged from 0.50‰ to 5.07‰. Peak values of δ¹⁸O and δ²H were in late summer, but values peaked 1 month later at the South Island sites, likely due to greater snow-melt contributions to streamflow. Strong spatial differences in river water δ²H and δ¹⁸O caused by orographic rainfall effects and evaporation may inform studies of water mixing across landscapes. Generally distinct seasonal isotope cycles, despite the large catchment sizes of rivers studied, are encouraging for transit time analysis applications.  相似文献