级配不连续粗粒土渗透变形试验缩尺方法研究

目前,基于试样的干密度、抗剪强度、变形特性和渗透性等效,提出了各种粗粒土试验超粒径颗粒缩尺方法,但对渗透变形试验中超粒径颗粒的处理并没有明确说明。通过采用不同缩尺方法对具有不同渗透稳定性的级配不连续型粗粒土进行渗透变形试验,并与原级配土的试验结果进行对照,分析了各类缩尺方法对渗透变形试验的适用性。结果表明:对于缺级粒径小于5 mm的级配不连续型土,等量替代法不影响粗料的绝对孔隙体积和细料填充程度,对管涌型和流土型土进行缩尺处理不改变试样的渗透破坏形式和水力条件;相似级配法因土体粒径的等比例减小使反映粗料孔隙尺寸的特征粒径D20相应变小,对管涌型土进行处理后渗透破坏形式转变为过渡型,流土型土的渗透破坏形式虽不会发生改变,但土颗粒离散程度的增大使相应的临界和破坏坡降明显降低;等量替代法能取得优于相似级配法的缩尺效果。

Scaling method of gap-graded coarse-grained soil in seepage deformation test

A series of scaling methods for oversize particles in geotechnical test of coarse-grained soil are proposed based on equivalence of dry density, shear strength, deformation and permeability, however the treatment to oversize particle in seepage stability test is not clear. Various scaling methods were used to perform seepage deformation tests on gap-graded coarse-grained soils with different seepage stabilities. As a comparison to these treated materials test results, some original-gradation materials tests were also carried out in order to analyze the applicability of different scaling methods to seepage stability test. The test results illustrate that for the gap-graded soil with gap-graded size below 5 mm the seepage failure type and hydraulic condition of piping or flowing type soil treated by the equivalent alternative method is the same as original-gradation materials, because of unchanged pore volume of skeleton and filling degree of fines. The similar grading method would make a proportional decrease to soil particle as well as characteristic particle size D20 that reflects pore size of coarse particle, thus resulting in piping type soils transformed to transition failure. The similar grading method would not change flowing type soils′ seepage failure type, but can reduce the critical damage gradient due to increase of soil discrete level. The equivalent alternative method can get better scaling effect than the similar grading method.