基于球形硅微粉的新型透明黏土基本力学特性试验

Basic Mechanical Properties of Transparent Clay Made from Spherical Silica Powder:An Experimental Study

透明土试验技术是近年来发展起来的一种新的变形可视化技术,包括透明土的制备和图像捕捉与处理方法等。通过此技术可以对透明土体内部的变形和渗流过程进行观测以实现土的三维变形、强度和渗流等问题的可视化研究。目前应用最多的透明土有2种:第1种是以熔融石英砂为土骨架,正十二烷和15#白油的混合溶液配制透明砂土,第2种是利用无定型硅微粉配制的透明黏土。透明砂土已经有了较成熟的研究,然而针对透明黏土的研究还不够成熟和深入,应用光学技术搭配透明介质研究土体三维变形和流动规律时,有两点要求不可忽略,一是透明土需要通过激光束对其进行切面,再利用数字照相技术进行图像采集与分析,因此配制出的透明土透明程度要高;二是配制的透明土其基本力学特性要与真实土体性质接近。目前所研究的透明黏土存在透明度不高,强度太低等诸多问题。为此,选取球形硅微粉作为透明土骨架材料,15#白油与正十二烷溶液混合溶剂作为孔隙流体配制新型透明黏土,对新型透明黏土进行直剪试验、一维压缩试验以及渗透试验,研究配制的新型透明黏土用于模拟真实黏土的可行性。试验结果表明:以球形硅微粉为土骨架,15#白油与正十二烷溶液混合溶剂作为孔隙流体制作的新型透明黏土,其土体的强度特性和压缩系数与粉质黏土特性相似,可以满足模型试验要求。

Transparent-soil experiment technology is a new deformation visualization technology developed in recent years.It involves the craftsmanship of transparent soil and particle image velocimetry(PIV)methods,which can be used to visualize the three-dimensional problems of deformation,strength,and flow.At present,the most widely used method involves the use of a mixed solution of n-dodecane and 15#white oil with fused quartz sand as the soil skeleton.Another method used amorphous silica micropowder to prepare the transparent soil.Although transparent sand has been widely studied,an in-depth research on transparent clay is lacking.When the optical technology and a transparent medium are applied to study the three-dimensional deformation and flow law of soil,the following two requirements cannot be ignored.First,the laser beam emitted by the laser transmitter is used to cut the transparent soil and an industrial camera is used to collect images.Finally,the PIV software is used to analyze and process the collected images.Therefore,the prepared transparent soil must ensure good transparency.Second,the mechanical properties of the prepared transparent soil should be close to those of natural soil.At present,the transparent clay studied has many problems,such as low transparency and low strength.In this study,direct shear,1-D consolidation,and permeability tests of the transparent clay prepared with spherical silica powder as the soil skeleton and a mixed solvent of 15#white oil and n-dodecane solution as the pore fluid were conducted.In addition,the feasibility of using transparent clay to simulate natural soft soil is studied.The experimental results demonstrate that the strength characteristics and compression coefficient of the soil of the transparent clay prepared in this study are similar to those of silty clay,and can thus meet the requirements of the model test.