重塑黄土的湿陷性与微观试验研究

Study on Collapsibility of Remolded Loess by Model Test and Evaluation of Loess Collapsibility

黄土广泛分布于中国西北地区。随着人类社会的发展,越来越多的工程项目需要在黄土地区展开。黄土的特殊性质导致其具有水敏感性,这种水敏感性的典型表现便是湿陷;而黄土的湿陷与其微结构的变形过程紧密相关。以重塑黄土为研究对象,在反复湿陷试验的基础上,对不同含水量、不同湿陷次数的重塑黄土试样进行CT扫描与电镜扫描等微观试验,结合IPP图像处理软件对微观试验结果进行定性与定量分析,得到重塑黄土湿陷性与其微结构的关系。认为:(1)黄土的自重湿陷系数主要受其含水量的影响,即含水量越小,越容易湿陷;且当含水量为6%时试样具有二次湿陷性;不同含水量的试样随着湿陷次数的增加,湿陷系数逐渐减小,且经过3次湿陷后其自重湿陷系数均趋于一个稳定的值;(2)随着湿陷次数的增加,土体中大的团粒与大孔隙逐渐消失,土体密度逐渐均匀,颗粒丰度逐渐变大,孔隙颗粒面积比逐渐减小,颗粒定向角度逐渐趋于水平;(3)黄土发生湿陷的主要原因是水的浸润或溶滤作用导致其结构强度的弱化,使大的团粒逐渐崩解成小颗粒填充到孔隙中造成土体压密。

Loess widely distributed in northwest China,more and more projects have been started in the loess areas with the development of human society. The loess has water sensitivity because of its special properties,and collapsibility is the typical manifestation of its water sensitivity. Collapsibility is closely related with the deformation process of its microstructure. Reshaped loess was take as the Research object on the basis of the collapsibility test repeatedly. Experiment reshaped loess of different water content and collapsibility numbers with CT and electron microscope scanning test and qualitative and quantitative analysis of loess microstructure parameter with IPP,the following results was achieved：（1）The coefficient of self-weight collapsibility mainly depends on its initial water content,means that the smaller water content is,the more easily soil collapse; and when the moisture content is 6%,the collapsibility is secondary; coefficient decreases gradually with the increasing of collapse times until tends to a stable value after three times＇ collapsing.（2）With the increasing of collapse times,large pores and large gradually disappeared,soil density uniformed gradually,soil grain abundance increased gradually,pore and grain＇s area ratio decreased,grain orientation angle tended level gradually.（3）The main reason of collapsibility is the infiltration and leaching of water,which weaken the strength of the structure and made big soil grain disintegrated into small particles which then filled to the pores gradually,caused of soil consolidation.