强震作用下抗震陷黄土改良地基的微观特征分析

基于动三轴试验和SEM细观结构测试试验,结合图像分析处理软件,对强震荷载前后宝兰客运专线沿线典型震陷性黄土及其经物理、化学和复合改良方法处理后的试样进行微观尺度的结构变形演化规律研究,探讨不同改良方法对土体微结构的影响及其与震陷系数之间的内在联系。结果表明:(1)物理改良方法对于消除大孔隙和架空孔隙结构的效果最为明显,同时对颗粒级配和结构也有调整;(2)化学改性方法则从颗粒接触方式、粒间胶结程度等方面影响土体强度,且不同化学反应的参与可生成独特的玻璃微珠或絮凝状细结构,从而大大提升土体某项参数指标,进而在强震中分别起到填充、胶结或缓冲作用;(3)强震作用前后不同改良方法对各微观要素的改变与相应的残余应变现象吻合较好,说明微结构能有效反映改良黄土残余变形的强弱。

Microscopic Characteristics of Improved Aseismic Subsidence Loess Foundations under Strong Earthquakes

To evaluate the relationship between micromechanisms and different physical and chemical improvement methods on the seismic subsidence loess engineering site, soil samples were obtained along the Baoji-Lanzhou High-speed Railway, and dynamic triaxial and SEM microstructural tests were conducted. Combining image processing software with the appropriate threshold, the evolution law of microstructure deformation of samples was applied and studied. Results showed that:(1) Physical improvement is the most effective way to eliminate macropores and porous pore structures; moreover, the particle size distribution and structure can be also adjusted. (2) Chemical modification affects the strength of the loess from the aspect of particle contact and intergranular cementation; moreover, the participation of different chemical reactions can produce unique glass beads or flocculent fine structures, which can greatly reinforce the strength of loess and play a role in filling, cementing, or buffering in strong earthquakes. (3) The differences between loess microcosmic parameters and residual strain coefficients, with the above improved methods before and after strong earthquakes, were compared, and it was found that they are in good agreement, indicating that the microstructure can generally reflect the residual deformation strength of the loess.