Microstructural Analysis Of Collapsible Loess Before And After Treatment

With the rapid development of the economy, the construction industry has more and more opportunities for development in the loess region. As we all know, in the Loess Plateau, there are many mountains and rare plains, which leads to the shortage of land in the project construction. When the natural foundation does not meet the engineering requirements, most builders have to complete the project under complicated geological conditions. However, the loess has its own special natures. If the collapsibility of soil can not be fully considered or not be dealt with correctly, it is easy to cause accidents, and harm to the country and the people.At present, common methods to treat collapsible loess include dynamic compaction, compaction column method and so on. These methods have achieved a certain effect. But studies are more concentrated on construction skills and macro effect than internal soil structure. Therefore, this article studied on the microstructure changes of collapsible loess roadbed from Pingyang high-speed. The contact between microscopic structure of the soil and its engineering properties is established by combining qualitative analysis with quantitative calculation. From the level of the soil microstructure, the effect of reinforcement treatment is judged. This paper focuses on this theme, completed the experimental study, image analysis, data processing work, and obtained the following conclusions:1) By comparing indicators of dry density, void ratio and coefficient of collapsibility of natural loess and treated loess, it can be macroscopically summaried that after treatment, the microstructure of loess soil turned dense from loose, its collapsibility is improved, but the degree of improvement is reduced as the depth increases.2) Based on considering the special properties of the loess, the five stages of work have been done for making the loess microscopic sample, including selecting the sample, drying the samples, soaking and hardening the samples, cutting and polishing the samples, plating film for the samples. By means of a scanning electron microscope, a series of microscopic images in different magnification are collected. After matching, middle magnification is selected as basis for qualitative analysis and quantitative calculation of microscopic image for loess sample.3) As a start to type, connection, and arrangement position of unit, the microstructure of loess at different depth is analyzed and described. The study show that there are multiple factors effecting the loess collapsibility such as the deposit of overhead pore, different cementation degree.4) With the help of image processing software such as Matlab and IPP, microscopic image parameters of the loess soil are calculated and analyzed, the changes of the loess soil’s pores before and after treatment are studies. The average pore size is proposed as a classification standard. For Pingyang highway project, the collapsibility of the loess soil is closely related to the pore with a diameter greater than50μm.5) By studying the orientation characteristics of loess porosity and shape feature, it is concluded that the stronger the loess soil is treated, the weaker the orientation characteristics of the soil pore is. Directional indicators and shape indicators can be used as an important basis for judging the reinforcement effect.