Model Size Effects in Centrifuge Models of Granular Slope Instability
Model Size Effects in Centrifuge Models of Granular Slope Instability
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DOI：
10.1520/gtj10353j
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发表时间：
1996-09
影响因子：
1.6
通讯作者：
D. Goodings;D. Gillette
中科院分区：
文献类型：
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作者：
D. Goodings;D. Gillette
土工实验室测试背后的两个假设是：第一，土壤颗粒足够小，在全尺寸现场情况下表现为连续体，在小型实验室测试中也表现为连续体;第二，实验室测试中的侧边界效应可以忽略不计，或者，如果不能忽略不计，不占主导地位的行为，但可以量化，以便对其影响进行校正。本文介绍了61个离心模型边坡破坏的数据，以评估侧边界和粒度对模型性能的影响。选用三种不同粒径的颗粒土，建立不同尺度和宽度的模型。通过增加自重使模型边坡破坏，这模拟了在保持边坡几何形状的同时增加全尺寸高度。为了模拟具有粘性的土壤的行为，使用真空对土壤施加小的负孔隙压力。模型以宽而浅的斜坡破坏而失败。晶粒尺寸对模型行为有两种影响。首先，看来模型破坏“表面”可能必须在土壤表面以下超过30个粒径，才能忽略粒度效应。其次，模型结果的重复性也受粒径的影响：当坡高大于等于158个粒径时，单组相同模型破坏数据的变异系数小于等于10%;对于高度为56粒直径或更小的较小模型斜率，变异系数显著增加。当检查模型宽度的影响时，看来，模型宽度可能必须超过模型边坡高度5倍，才能使浅宽边坡破坏不受侧边界阻碍地发展。
Two assumptions behind geotechnical laboratory testing are: first, that soil with grains small enough to behave as a continuum in a full-scale field situation will also behave as a continuum in a small laboratory test; and, second, that side boundary effects in a laboratory test are either negligible or, if not negligible, do not dominate behavior but are quantifiable so that a correction can be made for their effects. Data are presented here from 61 centrifuge models of slopes brought to failure to assess side boundary and grain-size effects on model behavior. Three granular soils of different grain sizes were used to build models of different scales and widths. Model slopes were brought to failure by increasing self-weight, which simulates increasing full-scale height while maintaining slope geometry. To simulate the behavior of soil with cohesion, a small negative pore pressure was applied to the soils using a vacuum. Models failed with wide, shallow slope failures. There were two effects on model behavior arising from grain size. First, it appears that the model failure “surface” may have to be more than 30 grain diameters below the soil surface before grain-size effects are negligible. Secondly, the repeatability of model results was also affected by grain size: coefficients of variation in failure data for a single group of identical models were 10% or less when slope height was 158 grain diameters or greater; coefficients of variation increased markedly for smaller model slopes with heights 56 grain diameters or less. When effects of model width were examined, it appears that model width may have to exceed model slope height by a factor of 5 for shallow wide slope failure to develop unimpeded by side boundaries.