西峰塬黄土的湿陷性研究

采用双线法对西峰塬原状Q3黄土进行增湿、减湿情况下的压缩试验。分析了黄土的湿陷变形随湿度及压力的变化规律。利用SEM技术测试了黄土湿陷前后的微结构变化,采用微结构定量化分析方法和分形分维集合方法分析了黄土试样微观孔隙的变化规律。结果表明:(1)黄土湿陷性的产生是构成黄土架空孔隙的刚性结点变异导致。(2)同级压力下超越湿陷率随初始含水量的增加而变大; 初始含水量在同一水平下,随压力的增加超越湿陷率逐渐变大。(3)黄土湿陷过程伴随孔隙数量大幅增加,平均孔径减小,孔隙面积缩小,大中孔隙数量骤降; 孔隙结构变得更加复杂。本文提出了黄土超越湿陷率的概念及受外界因素的影响规律,分析了非饱和黄土的湿陷机理,即水分和外力不同组合情况的湿陷性。

UNIAXIAL COMPRESSION AND SEM TESTS FOR LOESS COLLAPSIBILITY AT LOESS PLATEAU OF XIFENG

The behavior of undisturbed loess in the case of moistening or demoistening is investigated using double-line uniaxial compression test in this paper. The collapsible deformation rules of collapsible loess are examined and analyzed, during the growth process of humidity and pressure. And the microstructure of the samples are tested using SEM technique. Furthermore the microstructure of samples is analyzed with quantitative method and fractal theory. The results are shown the followings:(1)Rigid node failure of trellis pores can cause the loess collapsibility.(2)Water content of loess has a marked effect on its collapsible deformation. When pressure is some value, its exceeding collapsible probability can increase as moisture content increases. Similarly, the test data show that for loess with constant water content, its exceeding collapsible probability can increase gradually as pressure increases.(3)The average number of pore of sample obviously increases and the pore area decreases after the sample is collapsed. The collapse is a process that small pore increases, fractal dimension decreases, and complexity of the pore increases. The concept of the exceeding collapsible coefficient is put forward. An analysis is made on some issues about study of hydrocompaction from the view point of unsaturated soil mechanics. Finally a case study is given. It reflects the properties of collapsible deformation under different factors.