砂雨法制备三轴砂样的影响因素及均匀性研究

Factors and Homogeneity of Triaxial Sand Specimens Preparation with Air Pluviation

为了得到较为真实的室内重塑砂土样,利用自制的落砂装置,开展一系列福建标准砂的砂雨法制样试验,研究落距、漏斗管径和细颗粒含量等因素对室内土工三轴试验砂样制备的影响。结果表明:砂样相对密度随落距的增加而增加,而增速随落距的增加逐渐变缓并趋于稳定;相同落距下,漏斗管径越大,砂样的相对密度越小;漏斗管径的减小,可以得到较宽范围的砂样密度;随着砂土中细颗粒含量的增加,制备的砂样相对密度减小。利用牛顿第二定律和能量守恒定律能够较好地阐释落距、漏斗管径和细颗粒含量等因素对砂土制样的影响规律。采用225k V-3D微分辨率ICT对砂雨法制备的砂样进行细观扫描,并借助Image J软件,重构砂样三维模型,计算出沿砂样高度方向的每层孔隙占比,验证了砂雨法制备砂样的空间均匀性,并给出砂雨法制备室内三轴试样的合理化建议。

The influences of drop height, funnel diameter and fine particles,contents on sand specimen preparation for indoor geotechnical triaxial test were studied through preparation test of Fujian standard sand with self-manufactured air pluviation device. Results showed that the relative density of sand specimens increased with the increasing of drop height, and the growth rate slowed down and tended to be stable. The relative density of sand specimens decreased along with the increase of funnel diameter under the same drop height. A wider range of relative density can be achieved with the decrease of funnel diameter. The relative density of sand specimens decreased with the increasing of fine particles, contents. The influences of drop height, funnel diameter and fine particles,contents on the relative density of sand specimens can be well explained by Newton, s second law and conservation of energy. The gray image scanned with the 225 kV micro-computerized tomography of sand specimens prepared by air pluviation was analyzed by ImageJ software. The spatial homogeneity of sand specimens can be verified by reconstructing the three-dimensional model of sand specimens and calculating the proportion of sand pore area along the height of sand specimen. Furthermore, reasonable suggestions on preparing triaxial sand specimens were proposed.