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Study on Three-dimensional Characteristics of Fill Failures for Safety Evaluation

充填破坏三维特征安全评价研究

基本信息

批准号：
06650551
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 General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

In order to study three-dimensional failure characteristics of fill and ground, centrifuge loading tests were first performed on level and slope sand foundations by changing the size of rectangular footing (zeta=L/B). Some remarks drawn in these tests were as follows ; (1) brittle failures showing sharp peak of load-settlement curve are observed as zeta increases, while the variation of the ultimate values of bearing capacity is small, (2) the shape factor reduces due to the decrease in zeta for level ground as proposed by DeBeer, whereas little change is seen in bearing capacity for slope foundation, (3) the size effect in the bearing capacity is observed in both level and slope foundations, (4) the existence of slope shows large difference in load bearing capacity, giving the value of 0.5 to 0.6 for the ratio between slope and level grounds ; (5) faiure surfaces observed in loading tests on sloping ground are clearly defined and they can be approximated mathematically in good accuracy by use of log-spiral curves.In another series of centrifuge model tests for three-dimensional failure aptterns of earthfills constructed on the sloping valley, model fills were forced to slide by moving the front suppporting wall during a constant centrifuge circulation, and sliding planes were determined after the circulation stops by surveying the positions of intersecting points of noodle-type strings embedded in the model fill. It was recognized in the tests that (1) the size of sliding bodies, their depth and horizontal extension, becomes large as the width of the valley increases because of the decrease in the effect of lateral constraint, and (2) similar tendency is observed in the conventional stability analysis for the observed sliding plane, the three-dimensional safety factors becoming close to the two-dimensional ones as the valley with increases.

为了研究填土和地基的三维破坏特征，首先通过改变矩形基础的尺寸(ZETA=L/B)，对水平和斜坡砂基进行了离心机加载试验。在这些测试中得出的一些评论如下：(1)随着Zeta的增大，荷载-沉降曲线呈现尖峰的脆性破坏，但极限承载力变化不大；(2)由于DeBeer提出的水平地基Zeta的减小，形状系数减小，而斜坡地基的承载能力变化不大；(3)水平地基和斜坡地基的承载能力均存在尺寸效应；(4)斜坡的存在使承载能力差异较大，使斜坡与水平地基的比值在0.5~0.6之间；(5)倾斜地基加载试验中观察到的滑动面轮廓清晰，用对数螺旋曲线可以很好地对其进行数学逼近。在另一系列斜谷填土三维破坏的离心机模型试验中，通过在离心机循环过程中移动前支撑壁来强迫模型填方滑动，并通过测量模型填方中面状线串的交点位置来确定循环停止后的滑动面。试验结果表明：(1)由于侧向约束的影响减小，滑体的大小、深度和水平伸长都随着沟谷宽度的增大而增大；(2)常规的滑动面稳定分析也有类似的趋势，三维安全系数随着沟谷的增大而向二维安全系数靠拢。