某大厦深基坑开挖与施工安全监测实践与体会     

陆锦标 《现代测绘》2005,28(5):17-19

从深基坑安全监测实例出发,介绍了一种简便、易行、稳定、可靠的射线形水平位移基准网,同时适用用小角法高精度位移监测.另外就温度的变化对水平位移值的影响,降水施工对地面沉降,深层土体位移的影响及测斜管埋设的重要性提出了自己的观点、认识与体会,希望对类似工程有一定参考价值.  相似文献   

国土资源行业“3S”技术集成研究及实用技术体系构建     

查宗祥  刘聚海  蒋文彪 《国土资源信息化》2005,1(6):2-7

本文面向国土资源信息化建设的实际需求,通过关键技术研究和技术集成,建立基于“3S”的国土资源数据获取、更新、管理、交换与应用的技术体系,通过应用示范研究,形成实用、可推广的技术流程和应用软件。研究结果表明,基于“3S”的技术体系,以其精确的空间定位、快速准确的数据获取、强大的数据管理能力,能够满足国土资源信息化建设的实际需要。  相似文献   

Exploring the spatial and temporal dynamics of land use in Xizhuang watershed of Yunnan, southwest China     

Xu Jianchu  Ai Xihui  Deng Xiqing 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):299-309

Over the last two decades, China has introduced a series of agricultural and forestland use reforms, aiming to feed the largest population in the world and maintain ecological services locally and nationally. This paper studies the impacts of local government-driven reforestation on land use and land cover change, as well as its further impacts on livelihoods of upland farmers in Xizhuang watershed. An analysis of aerial photographs and ASTER satellite imagery from 1987 to 2002, respectively, showed that the forest has significantly increased at the expense of decreasing farmland. However, the monoculture reforestation of pine has caused both biophysical and socio-economic consequences. This case study also shows forestry decentralization in China remains incomplete. Land use and land cover change is also a political economic issue. Some of the reforms designed to protect forest resources have had a negative impact on rural livelihoods.  相似文献   

Land-use classification using ASTER data and self-organized neutral networks     

《International Journal of Applied Earth Observation and Geoinformation》2005,7(3):183-188

Operationally AVHRR and TM/TM+ data were used and a supervised maximum likelihood classification (MLH) was applied to depict land use changes in Beijing, providing basic maps for planning and development. With rapid growth of the city these are helpful to deal with higher resolution data, whereas new classification algorithms produce land use maps more accurate. In the paper, new sensor ASTER data and the Kohonen self-organized neural network feature map (KSOM) were tested.The TSOM classified 7% more accurately than the maximum likelihood algorithm in general, and 50% more accurately for the classes ‘residential area’ and ‘roads’. The results suggest that ASTER data and the Kohonen self-organized neural network classification can be used as an alternative data and method in a land use update operational system.  相似文献   

土壤热异常对地表能量平衡影响初探   总被引：3，自引：1，他引：3  

郭维栋  孙菽芬 《气象学报》2002,60(6):706-714

将来自土壤深部的热通量引入off line的陆面过程模式 (NCAR—LSM ) ,通过长达 2a的数值试验对比分析了它对各层次土壤温度和地表能量平衡的影响。　　在土壤底部引入 5W /m2 的热通量使底层土壤显著升温 ,但升温随着接近表层而迅速衰减。积分 3个月后 ,由地下进入地表的热流量增幅可达 1W/m2 以上 ,并持续增大到 5W /m2 ,地表最大升温约 0 .5K ,同时地表感热、蒸发潜热及长波辐射通量均有 1W /m2 左右的正异常 ;若将土壤热传导系数放大一个量级以加速热量交换 ,则地表升温提高到 1K以上 ,长波辐射增加 3W /m2 以上 ,超过了气溶胶全球平均的辐射效应。结果表明 :一定量值的土壤热异常对地表能量平衡和短期气候变化 (10 -1～ 10 1a)有着不可忽略的影响。同时 ,深入的资料分析、完善的陆面过程模式以及它与大气模式的耦合试验也是亟待进行的相关工作。  相似文献   

典型干旱地区陆面特征的模拟及分析   总被引：14，自引：15，他引：14  

王澄海  董文杰  韦志刚  马文婷 《高原气象》2002,21(5):466-472

运用NCAR -LSM (Landsurfacemodel)模式对典型干旱区—沙漠站进行了独立试验 (Off line) ,检验了LSM模式在典型干旱地区的性能 ,并分析了典型干旱地区的陆面特征。结果表明 :LSM模式对干旱地区有较好的模拟性能。在不同的季节 ,典型干旱地区的感热和潜热有着不同的特征 ,4月份的感热通量较大 ,约为 4 0 0W·m-2 ;1月和 8月相对较小 ,约为 2 30W·m-2 。 1月和 4月的潜热通量很小 ,约为 4～ 6W·m-2 ,可以忽略 ;但 8月份的潜热通量大 ,平均最大约为 12 0W·m-2 ,当有降水发生时 ,潜热通量可达 5 70W·m-2 ,与感热通量相当。  相似文献   

计算非均匀地表通量的一种简化PDF及其应用   总被引：2，自引：4，他引：2  

刘晶淼  王纪军  丁裕国 《高原气象》2002,21(6):583-590

提出描述地表非均匀特性的简化概率密度函数（PDF），它可代替各种具体的PDF用于求解次网格尺度平均通量而不影响其精度，这种简化PDF可直接加入陆面过程模式方程组中进行陆－气通量交换的数值试验。它对非均匀地表陆面过程参数化具有一定的普适性。本文仅讨论了对称分布的简化计算（非对称分布另文讨论），列举了非均匀分布的观测事实，并以地表净红外辐射通量计算为例，详细验证了应用这种简化PDF的可行性和可靠性。  相似文献   

土壤热异常影响地表能量平衡的个例分析和数值模拟   总被引：6，自引：0，他引：6  

Guo Weidong  Sun Shufen  Qian Yongfu 《大气科学进展》2002,19(3):500-512

The statistical relationship between soil thermal anomaly and short-term climate change is presented based on a typical case study. Furthermore, possible physical mechanisms behind the relationship are revealed through using an off-line land surface model with a reasonable soil thermal forcing at the bottom of the soil layer.In the first experiment, the given heat flux is 5 W m-2 at the bottom of the soil layer (in depth of 6.3 m)for 3 months, while only a positive ground temperature anomaly of 0.06℃ can be found compared to the control run. The anomaly, however, could reach 0.65℃ if the soil thermal conductivity was one order of magnitude larger. It could be even as large as 0.81℃ assuming the heat flux at bottom is 10 W m-2. Meanwhile, an increase of about 10 W m-2 was detected both for heat flux in soil and sensible heat on land surface, which is not neglectable to the short-term climate change. The results show that considerable response in land surface energy budget could be expected when the soil thermal forcing reaches a certain spatial-tem poral scale. Therefore, land surface models should not ignore the upward heat flux from the bottom of the soil layer. Moreover, integration for a longer period of time and coupled land-atmosphere model are also necessary for the better understanding of this issue.  相似文献   

上海软粘土微观特性及在土体变形与地面沉降中的作用研究   总被引：18，自引：3，他引：18  

龚士良 《工程地质学报》2002,10(4):378-384

对上海软粘土的颗粒及集合体成分、孔径分布、微结构、孔隙溶液与阳离子交换性作了分析 ,对固结前后的孔径变化与人工回灌对土体性质可能带来的影响作了探讨 ,从物理化学角度阐述了软粘土微观特性对土体固结变形及地面沉降的影响.  相似文献   

一维地面沉降模型及其求解   总被引：10，自引：1，他引：10  

张云 《工程地质学报》2002,10(4):434-437

推导了以垂向有效应力为基本变量的一维地面沉降的普遍模型 ,并用半解析方法予以求解。模型考虑了土体变形过程中渗透系数和压缩性随有效应力的变化而变化的特性 ,反映了土体变形的非线性特征。计算实例表明 ,该模型的计算结果比太沙基方法的计算结果有了很大程度的改善 ,与实际情况非常接近。  相似文献