排序方式: 共有26条查询结果,搜索用时 15 毫秒
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为了研究河口海岸地区淤泥的运动规律,以天津塘沽地区淤泥为研究对象,采用理论分析与水槽实验相结合的方法,讨论了流变参数与密度之间的关系,总结出宾汉极限剪应力、粘滞系数与密度的关系均符合指数分布并给出关系式.研究了不同底床密度和水流条件下淤泥的起动及冲刷规律,得出淤泥的起动符合希尔兹曲线,随淤泥密度增大,起动流速相应加大;... 相似文献
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小浪底水库投入运行以后,黄河下游河道地貌发生巨大变化,滩区治理面临土地保护与开发利用之间的矛盾。本文基于地形空间插值与实测资料研究了花园口-高村宽滩游荡型河段在2000—2017年间的泥沙分布特征及滩区地貌演变情况,并提出滩区改造方案。研究发现,由于小浪底水库拦沙作用,长期低含沙水流下泄导致河床形态调整加剧,主槽冲刷明显,洪水漫滩几率降低;下游河道生产堤及控导工程的修建,加上土地开发利用及其他人为活动影响,滩区逐渐从沉积模式转为侵蚀模式;花园口-高村河段在2000—2017年累计侵蚀11.373亿m~3,其中滩地侵蚀约2.145亿m~3。为了沿黄经济带发展与滩区生态建设,有必要采用机械放淤、填方再造等手段对下游滩区进行分区改造,优化土地资源利用。 相似文献
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Istanbul is the largest city in Turkey with an area of around 5750 km2 and population of around 10.58 M (2000). The population is increasing because of mass immigration. Planned and unplanned housing are increasing while green areas are decreasing in area. Rapid, uncontrolled and illegal urbanization accompanied by insufficient infrastructure has caused degradation of forest, water basin and barren lands in the metropolitan area, especially within the past two decades. The study includes taking administrative planning decisions about the development of urban sustainability in the metropolitan area of Istanbul, producing rationalist solutions to the problems in environmental and natural resources, and conservation of small-scale (historical, tourist, residential, industrial, etc.) specific urban areas. By the help of this study, settlement suitability analyses have been achieved according to the natural thresholds of the area. Additionally, some kinds of formations, which may limit the development of the metropolitan area of Istanbul, such as natural structures, natural structure, ecological corridors and natural hazard areas, have been defined and developed model on the ArcGIS 9.1 platform. In the light of the policies of the European Union about sustainable cities, environmental impact assessments and sustainability policies have been determined for both the existing settlements and sustainable development areas. 相似文献
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《Construction and Building Materials》2010,24(9):1790-1795
Compacted sand concrete is being researched for potential usage in road construction because of shortage in gravel resources in many countries. However, one of the problems for this material with such application is shrinkage cracking. This paper presents the results of the unrestrained shrinkage test performed on three different compacted sand concrete mixes. Two existing shrinkage prediction models, namely the ACI 209 and the CEB 90, were used to fit the measured shrinkage data. The CEB 90 model with an application of a correction factor was found to perform well with compacted sand concrete. Based on the results of the shrinkage tests, joint spacing between compacted sand concrete slabs was calculated. 相似文献