非饱和堆积碎石土细小黏粒微观结构研究

堆积碎石土中细小黏粒因入渗过程中含水率差异，其微观结构发生改变而直接影响碎石土的渗透特性。考虑不同含水率对孔隙特征（尺度、排列、形态）的影响，借助扫描电镜和PCAS微观定量测试技术，对水竹湾隧道洞口斜坡堆积碎石土中细小黏粒的微观孔隙特征进行了试验研究。研究结果表明：细小黏粒的孔隙度首先随含水率增加逐渐增加，当含水率达到12.5%时，土壤内部结构发生转变，孔隙度随含水率增加缓慢减小；随着含水率的增加气相孔隙度逐渐减少，小孔隙的数量明显增加，中孔隙、大孔隙数量却缓慢减少；不同含水率下孔隙定向角在10°~30°，50°~70°，100°~120°，140°~160°四个方位上分布相对密集，且含水率越小，孔隙有序性相对较差；概率熵与形状参数先随含水率的增加在含水率为7.5%~10%间出现峰值，再随含水率的增加而减少。通过分析不同含水率下碎石土细小黏粒微观结构参数的变化规律对宏观渗流特性影响，有助于明晰坡体渗流场的形成、碎石土强度指标降低等滑坡灾害问题。

Microstructures of the fine clay in aggregate gravel soil under unsaturated condition

Due to the difference of moisture content in the fine clay in aggregate gravel soil,the variation of microstructure in fine clay directly affects the permeability of aggregate gravel.Considering the influence of pore characteristics (scale,arrangement and pattern) in different moisture contents,the experiment was conducted to study the microstructure of the fine clay in aggregate gravel soil at a slope near Shuizuwan Tunnel by scanning electron microscope (SEM) and PCAS quantitative testing technology.The result show that:with the addition of moisture content,the porosity firstly increased and then decreased.When the moisture content increased to 12.5%,the moisture content reached to the maximum.Simultaneously,with the addition of moisture content,the gas porosity gradually decreased and the small pores increased obviously,but the medium pore and large pore decreased.The pore orientation angle under different moisture contents were concentrated in 10°-30°,50°-70°,100°-120°and 140°-160°,and the less moisture content,the less pore orderliness.Entropy probability and form factor increased with the increase of the moisture content,then peaked with the moisture content from 7.5% to 10%,then reduced with the increase of the moisture content.By analyzing the effect of the variation of the fine clay gravel soil microstructure parameters under different moisture contents on macroscopic flow characteristics,it is useful for understanding the formation of slope seepage field and the disasters of decreased strength index of landslide.