Research On Low Clay Mineral Mudstone Expansion Mechanism And Influence For High-speed Railway Subgrade

With the development of high- speed railway in C hina, many different and unexpected new problems will be appeared. Owing to the expansibility of the low clay mineral mudstone in the roadbed, part of the one a certain such high- speed railway is affected by upper arch disease. Compared with the existing high-speed railway design, construction and operation process.According to the 《Code for rock and soil classification railway engineering》(TB10077-2001) the mudstone is judged as no swelling characteristic or weak swelling characteristic rock, There are strict standards for settlement in 《Code for design of high speed railway》,but there is no standard for swelling number. Therefore, a new challenge was approved, the research on the mudstone was carried out. In the paper, the low clay mineral mudstone in the subgrade of the high-speed railway was taked as research target, various of experiment test were operated, for example, indoor experiment, in-situ test, indoor self-processed model test, microscopic scan analysis, theoretical analysis and numerical calculation. The deformation characteristics were studied systematically, and the expansion mechanism and engineering application of the low clay mineral mudstone which is used as the roadbed of high speed railway were discussed. These main research results were obtained as follows.(1)Take the low lay mineral mudstone for research subject, the fundamental characteristic of the original state and the reshaping sample were obtained, which included physical properties, mineral composition, geochemical composition, water physical properties, swelling properties and strength properties.The microscopic structure scanning experiments are carried out under different conditions,which including natural state and dry wet cycle, in order to get the change law of the microstructure of the mudstone in the case of water soaking and dehydration.(2) The high standard and strict requirement of the swelling deformation were considered, it put forward the mudstone expansion parameters and parameter values which are fit for the high speed railway typical swel ing subgrade.(3)The in-situ swelling deformation test in the typical subgrade section was carried out.e The swelling deformation of mudstone subgrade under different overburden loads and constraints could be obtained, the occurrence regularity of expansion deformation 、relationship between overburden load and expansion、relationship between immersion depth and expansion quantity、development process and development stage of expansion and deformation were analyzed.Then the effect of the overlying load on the expansion and deformation of mudstone were being discussed through indoor self-made testing equipment.(4) When the height of the overlying soil is different,The feasibility of the method for calculating the deformation of mudstone subgrade was verified and the maximum value of the swel ing deformation of the mudstone roadbed was analyzed.(5) The relationship between stress and strain、the relationship between stress and strain in elastic-plastic state theoretically considering the expansion deformation were deduced. A numerical simulation method considering the expansion force was established. Through the comparison and analysis of the numerical simulation and indoor test, the feasibility of the numerical model was verified, the numerical analysis of the typical swelling subgrade carried out and the expansion deformation of mudstone subgrade section was analyzed.(6)Take the two typical low clay mineral mudstone subgrade of the high-speed railway for example, and considering the results from laboratory test and field investigations, the causes were analyzed, influence factors and deformation mechanism of swelling subgrade could be obtained.