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Stability of a levee modelled in a geotechnical drum centrifuge.

在岩土转鼓离心机中模拟的堤坝稳定性。

基本信息

批准号：
60550342
负责人：
KUSAKABE Osamu
金额：
$ 1.28万
依托单位：
University of Utsunomiya
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550342/
关键词：
drum centrifuge model test stability of levee stability problems pipe flow パイプフロー相似則

项目摘要

The first drum centrifuge in Japan was designed and constructed to study the stability problems of long soil structures, such as embankments, levees. The drum has the diameter of 0.8 m , the width of 0.3 m and the depth of 0.1 m , and can be spinned up to 150 g, producing the prototype behaviour of a soil model of 377 m long, 45 m wide and 15 m deep. The achievement of this study can be summarized in the following points.1. Safety operation of the drum centrifuge has continued for over one thousand hours by the end of Feburary,1987, which gives us a confidence of utilizing a drum centrifuge as an useful experimental tool for modeling geotechnical problems.2. Experimental technique of production of a normally consolidated clay layer overlain by a levee of compacted soils in the drum has been established.3. Modeling technique of levee failures during flood has been sucessfully developed. A series of model tests with different soil type was carried out. Close observation suggests that the process of failure of a levee may be understood by using an analogy of stability of shallow tunnels. Observed process of failure was as follows:As the level of water raises, the first erosion is occurred at the surface of a levee slope, and that a pipe flow is created by hydraulic fracture and seeping water reaches at the surface of the levee slope on the inland side. As the result of flushing out the soil particles, the diameter of the pipe flow gradually widens. Our knowlegde of the stability of of a shallow tunnel tells us that the stability of the pipe is gorverned by the ratio of the cover of the pipe to the diameter of the pipe, and by the cohesion and the unit weight of the soil. For soils having higher cohesion, the pipe remains stable up to relatively larger diamter, whereas soils having less cohesion, the pipe collapes when the diamter becomes a certain value, resulting the total failure of the levee.

日本第一台转鼓离心机是为研究堤坝等长土体结构的稳定性问题而设计建造的。该鼓的直径为0.8米，宽度为0.3米，深度为0.1米，可旋转至150克，产生377米长，45米宽，15米深的土壤模型的原型行为。本研究的成果可以概括为以下几点.到1987年2月底，转鼓离心机已连续安全运行1000多小时，这使我们有信心把转鼓离心机作为模拟岩土问题的一种有用的实验工具.建立了在转鼓内形成正常固结粘土层和压实土堤坝的实验技术。防洪堤溃决的模拟技术已得到成功的发展。进行了一系列不同土类的模型试验。近距离观察表明，堤坝的破坏过程可以用浅埋隧道稳定性的类比来理解。观测到的破坏过程是：随着水位的升高，堤坡表面发生第一次冲刷，水力劈裂产生管流，渗透水到达内涝侧堤坡表面。由于冲洗出土壤颗粒，管流的直径逐渐变宽。对浅埋隧道稳定性的认识表明，埋管的稳定性主要取决于埋管与管径的比值、土体的粘聚力和容重。对于粘性较大的土体，管长较大时，管壁仍保持稳定，而对于粘性较小的土体，管壁在达到一定直径时，管壁会发生破裂，导致堤防的整体破坏。