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1.
Mohammad Rezwanul Islam Syeda Fahliza Begum Yasushi Yamaguchi Katsuro Ogawa 《Journal of Marine Systems》2002,32(4):73
Remote sensing technique was applied to estimate suspended sediment concentration (SSC) and to understand transportation, distribution and deposition of suspended sediment in the estuary and throughout the coastal sea, off the Ganges–Brahmaputra River mouth. During low river discharge period, zone of turbidity maximum is inferred in the estuary near the shore. SSC map shows that maximum SSC reaches 1050 mg/l in this period. Magnitude of SSC is mainly owing to resuspension of the bottom surface sediments induced by tidal currents flowing over shallow water depths. The influence of depth on resuspension is farther revealed from the distribution and magnitude of SSC along the head of Swatch of No Ground (SNG) submarine canyon. During high river discharge period, huge river outflow pushed the salt wedge and flashes away the suspended sediments in the coastal sea off the river mouth. Zone of turbidity maximum is inferred in the coastal water approximately within 5–10 m depth of water, where the maximum SSC reaches 1700 mg/l. In this period, huge fluvial input of the suspended sediments including the resuspended bottom sediments and the particles remaining in suspension for longer period of time since their initial entry control mainly the magnitude of SSC. In the estuary near the shore, seasonal variation in the magnitude of SSC is not evident. In the coastal sea (>5 m water depth), seasonal influence in the magnitude of SSC could be concluded from the discrepancy between SSC values of two different seasons. Transportation and deposition of suspended sediments also experiences seasonal variations. At present, suspended sediments are being accumulated on the shallow shelf (between 5 and 10 m water depth) in low discharge period and on the mid-shelf (between 10 and 75 m water depth) during high discharge period. An empirical (exponential) relationship was found between gradual settle down of suspended sediments in the coastal sea and its lateral distance from the turbidity maximum. 相似文献
2.
水库淤积的一种不利形态 总被引:1,自引:0,他引:1
水库效益发挥程度与水库淤积形态密切相关。三角洲淤积在实际水库中比较普遍,研究相对较多。文章利用数学模型计算,发现水库在前期三角洲淤积基础上还可能出现一种新的淤积现象,称为二级三角洲形态。通过大量分析,论证了这种不利形态产生的可能性、影响因素以及危害性。二级三角洲虽只是数学模型意义上的淤积形态,但由于其主要侵占兴利库容,对水库防洪和调节性能影响极大。同时,二级三角洲可能会大量抬升变动回水区的水位,大大增加库尾的淹没损失,危害极为严重。实际水库调度运行中应高度重视并严加避免。 相似文献
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挖入式港池泥沙淤积试验研究 总被引:1,自引:0,他引:1
在水槽试验的基础上,结合部分理论分析,初步研究了挖入式港池的泥沙淤积问题的原因、泥沙运动以及淤积特性。结果表明:含沙量分布具有一定的规律,口门处淤积量较大,泥沙粒径较粗,而港池内部淤积量较小,粒径较细。因此,采取适当措施减少该形式港池口门处的淤积是十分必要的。 相似文献
5.
Ports are drivers of regional and of countries’ economic development. Most ports are built close to coastlines, where waters are shallower and tend to suffer from deposit sedimentation processes, which reduce depths in operational areas. In presence of shallow waters and sedimentation, ports must decide whether to dredge or not, where both decisions have significant impacts on ports’ annual incomes. Nevertheless, there are seabeds, namely muddy bottoms, in which vessels can navigate with a safety degree. This paper aims at investigating the extent to which the theoretical knowledge of vessel’s control in muddy waters is valid at a certain nautical bottom, as defined by the Permanent International Association of Navigation Congresses (since 2009 the World Association for Waterborne Transport Infrastructure but the acronym stays PIANC) and its impact on port economics. To achieve the proposed objective, an email survey was sent to worldwide pilots that manoeuvre ships in muddy waters. The survey validated the theoretical knowledge, showed that navigation in muddy waters is possible, that it can contribute to reduce ports’ operational costs, and that the subject can be rather controversial. 相似文献
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以扬州市某条市政道路为例,介绍真空预压法加固软土地基沉降计算过程及各计算参数的取值情况;通过对软土区施工过程的沉降观测资料及工后对软土区的室内物理力学性质指标分析来看,采用真空预压法是可行的;其真空度的取值、固结度的选用是合理的,由此计算方法所得到的真空预压时间是正确的,其工后沉降满足规范要求。 相似文献
8.
The coastal zone is attractive for human settlement because it tends to be resource rich, providing a good location to generate incomes and livelihoods. Equally, however, it is a complex and powerful natural environment, which means that the coastal zone often becomes a focus of conflict with multiple users competing for limited space and resources. Understanding the causes of, and determining solutions to, the ensuing problems requires inputs from a range of analyses across sectors and disciplines. However, different disciplinary and sectoral approaches frequently use different investigative methods, language, and means of presenting results. This article presents a framework that has been developed in collaboration with Indian institutions over the past three years in an effort to address some of these fundamental problems of analysis and translation into policy action. Key components addressed by the framework are strengthening the capacity to practice, knowing how to proceed and how to find out what needs to be known using experience-based problem solving. 相似文献
9.
高速公路软土路基施工沉降及稳定性监测 总被引:2,自引:3,他引:2
介绍了软土路基施工中存在的主要问题和路堤施工软土路基观测的目的和内容,总结了路基沉降的观测方法及具体步骤,并结合高速公路工程实例,说明了软土路基沉降的观测方法在实际工程中的应用。 相似文献
10.
针对洞桩法暗挖车站跨既有隧道施工项目,通过增加施工通道,采用门式钢架加固等创新、改良工艺,解决了施工工序转换的难题,节约工程成本,降低施工风险。 相似文献