Research On The Micro-structure Change Of The Slide-zone Soil In Loess Landslide Caused By Train-induced Long-term Vibration

Due to the characteristics of the loess own structure, physical and mechanical properties, the loess landslides, seismic subsidence, dynamic loess settlement and other geological disasters along the highway and railway road occurred frequently and caused seriously endangering, they greatly hinder the rapid development of transport and then bring tremendous impact on the loess region's economic construction and social development.Based on the present research situation about micro-structure of loess, loess landslide slide-zone soil and soil dynamics at home and abroad, taking the loess landslide along the highway and railway as research subject, combined with laboratory tests, using qualitative and quantitative or semi-quantitative analysis method, the research on the micro-structure change of the slide-zone soil in loess landslide caused by train-induced "minor amplitude and long-term" vibration are carried out. The research work has accomplished with the following achievements.Firstly, on the basis of "group" feature of loess landslides in distribution, a new type of combination of the groups: Loess Landslide along the Highway or Railway, which leads to the main content of this paper, namely: train-induced vibrations caused micro-structural changes of Loess landslide slide-zone soil; Secondly, by imposing long time-sustained sinusoid loading on natural loess specimens which collected on Typical highway Landslide in dynamic triaxial test, characteristic of loess residual strain(dynamic subsidence) has been studied. The result shows that under different dynamic stress conditions, different samples' cumulate residual strain, dynamic shear strength exhibited regularly changes in the pattern of the change of vibratory times, consolidation stress and dynamic stress, also have their own peculiarity. And the slide-zone soil shows its vibration deformation behaviors only under greater main stress ratio;In addition, there are some scanning electron microscopy (SEM) test on these samples after dynamic triaxial test have been done. The SEM photo shows that undisturbed slide-zone loess have loose structure, irregular pore shape and lesser complete aggregate grain, and these grain intercoagulated and been massive shape, The contact relationship among the soil framework grain are mainly bracket contact, contact mode are mainly corner to edge contact; But after the dynamic triaxial test ,the structure of the samples become more compact and stable, loess pore break up and show the characteristic of orientation, and the quantity of soil macropore decreased significantly, and the contact relationship are mainly mosaic contact, contact mode are mainly edge to edge contact; Finally, Based on the Fractal theory and image-processing techniques such as Photoshop,Arcview,ArcMap, this paper researched the change of pore microstructure of loess under this type of dynamic load, the result shows that the pore microstructure of loess have the character of fractal, and the relation between microstructure parameter of loess sample and the load under different load condition have been studied, the research indicated that these parameters shows regular change along with the dynamic stress, main stress ratio, at last the linear relationship between these parameters and macro-mechanical properties of the slide-zone soil was founded due to the above result.