Behavior of pore water pressure and stability evaluation against seepage failure in earth slopes

土质边坡孔隙水压力特性及渗流破坏稳定性评价

基本信息

批准号：
15560432
负责人：
NARITA Kunitomo
金额：
$ 0.77万
依托单位：
Aichi Institute of Technology (A.I.T.)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560432/
关键词：
Centrifuge Model Test Rapid Draw-down Pore Water Pressure Seepage Failure Slope Failure Saturate Unsaturated Seepage Seepage by Rainfall Slope Protection

项目摘要

In order to study behavior of the residual pore-water pressure and its influence on slope stability in earth dams during a rapid draw-down of the reservoir water, centrifuge model tests were conducted on several model fills by realizing draw-down of the upstream water level under a constant centrifuge acceleration, in which small size transducers were installed in matrix for pore-water pressure measurement. Several different conditions to be supposed were set in the experiment to investigate influential factors on accumulation of the built-up pore-water pressure in embankments : that is, the case where the rate of draw-down is changed for the same type homogeneous embankments, the case where a thin impervious soil layer is set on the upstream face as an inclined core zone, and the case where a L-type drain is set to promote dissipation of pore-water pressure in the middle part of an embankment. Some failure tests, in which sliding failure is reproduced in the upstream slope, were also … More conducted to discuss instability of slopes caused by the increase of the residual pore-water pressure built up during draw-down. Concluding remarks drawn from the present study are summarized as follows : (1) In the case where the rate of draw-down of the reservoir water is high, drainage water from the interior to the up stream face is restricted even in a homogeneous dam, and the residual pore-water pressure develops in the upstream slope to have a large influence in slope stability. (2) In a dam with a thick impervious core zone, a discontinuous head difference appears in every state between the reservoir water level and the phreatic surface in the dam, due to little flow of drainage water to the upstream face. (3) Although the residual pore-water pressure reduces rapidly in the interior of an embankment by setting a L-type drain, it still shows high value in the surface part of the fill to the extent of the case without drainage facilities, and comparatively deep sliding failure passing through the crest appeared as the water level decreases.Another series of centrifuge tests were done on the behavior of seepage uplift pore-water pressure acting on the base of a river dyke resting on a permeable soil foundation, and discussion was made on the influence of the uplift pressure on such seepage failures of embankment as piping and loss of bearing capacity. Analytical studies were also performed by use of the FEM saturated and unsaturated seepage analysis, and a method of stability evaluation of earth slopes was proposed, by taking into account of distribution of pore-water pressure along a sliding plane and that of hydraulic gradient in the fill, from both view points of sliding failure due to pore-water pressure and seepage failure (hydraulic fracture) due to concentration of hydraulic gradient. Less

为了研究库水快速下降过程中土坝残余孔隙水压力的表现及其对边坡稳定性的影响，通过实现上游水位下降，对多个模型填土进行了离心模型试验。实验中设置了几种不同的假设条件，以研究在恒定离心加速度下的累积孔隙水压力的影响因素，其中在基质中安装小尺寸传感器进行孔隙水压力测量。堤坝：即同类型均质路堤改变水位下降率的情况、上游面设置薄层防渗土层作为倾斜核心区的情况、L型排水沟的情况为了促进路堤中部孔隙水压力的消散，还进行了一些在上游边坡上再现滑动破坏的破坏试验，以讨论残余增加引起的边坡失稳。本研究得出的结论总结如下： (1) 在水库水位下降速率较高的情况下，从内部向内部排水。即使在均质坝中，上游面也受到限制，上游边坡中剩余孔隙水压力的发展对边坡稳定性影响较大。 (2)在厚不透水核心区的坝体中，出现不连续的水头差。在每个州（3）虽然通过设置L型排水沟，堤内部残余孔隙水压力迅速降低。，在没有排水设施的情况下，在填土表层部分仍然表现出较高的值，并且随着水位的降低，出现了穿过顶部的较深的滑动破坏。渗流隆起分析了渗透性地基上作用于河堤底部的孔隙水压力，并讨论了抬升压力对路堤渗流破坏（如管道和承载力损失）的影响。利用有限元饱和和非饱和渗流分析，提出了一种考虑滑动面孔隙水压力分布和填土水力梯度分布的土质边坡稳定性评价方法。孔隙水压力引起的滑动破坏和水力梯度集中引起的渗流破坏（水力裂缝）的观点较少。