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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。
The double line method was used to compress the undisturbed Q3 loess in Xifeng Plateau under humidification and dehumidification conditions. The variation of deformation of loess with moisture and pressure is analyzed. The microstructure changes of loess before and after collapsing were tested by SEM, and the microscopic pore changes of loess samples were analyzed by microstructural quantitative analysis and fractal fractal dimension collection. The results show that: (1) Collapsibility of loess is caused by the variation of “rigid ” node which constitutes the aerial porosity of loess. (2) The overburden collapse rate increases with the increase of initial water content under the same pressure. The initial water content at the same level increases with the increase of pressure and the wet-fall rate becomes larger. (3) The process of loess collapsibility increases with the increase of the number of pores, the average pore size decreases, the pore area shrinks, the number of large and medium pores plunges, and the pore structure becomes more complicated. In this paper, the concept of loess overrun collapsing rate and the influence law by external factors are put forward. The collapsibility mechanism of unsaturated loess is analyzed, ie, the collapsibility of different combinations of water and external forces.