Study On Discriminant And Classification Of Expansive Soil In Ballastless Track Of High-speed Railway

In recent years,China’s high-speed railway has developed rapidly and became a bright business card of China.The construction of the high-speed railway project has been in the leading position in the world.But during the construction and operation of a high-speed railway in China,the continuous upper arch deformation of line is far beyond the 4mm limit of rail fastener,which has seriously affected the safe operation of the line.After analyzing the mudstone of its foundation,we found that only a few of the mudstones were classified as expansive soil according to existing railway and building discrimination standards and methods.Most of them were classified as "non expansibility".China Rail Corp organized experts and scholars analysing the causes of disease by many times,the unified conclusion is drawn: the low clay content of mudstone in the foundation really has expansive capacity.The existing railway swelling soil identification method is more suitable for general speed railways.For high standard and high speed ballastless track,it is still necessary to further improve the existing standards.Based on that high-speed railway engineering,laboratory tests and mathematical statistics are applied to the foundation mudstone for high-speed railway ballastless track expansive soil.The main research work is as follows:(1)X ray diffraction shows that clay minerals in mudstone in the foundation of disease section are less.Some mudstones don’t contain montmorillonite,but all mudstones contain illite and kaolinite.Therefore,the content of illite and kaolinite should be fully and comprehensively considered in the new discrimination.By reading the literature,they were converted to equivalent montmorillonite based on their hydrophilicity relative to montmorillonite,and combined with widely used cation exchange volume,liquid limit and free expansion rate as indicators of expansive soil.(2)Through a large number of experimental finds,the existing free swell test results are not only possible,because of the different testing personnel,test equipment and other reasons lead to unstable results,it is likely to appear in the same soil sample test has many free swelling ratio test results,which will bring trouble to the engineering and study,even cause serious losses.According to the test,a more stable and reliable test method is obtained to make the result of free expansion more stable and reliable.(3)A large number of indicators are analyzed and tested for the mudstone in the foundation of disease section.According to the principal component analysis method in mathematical statistics,a discriminant formula for expansive soil of ballastless track of high-speed railway is established.The discriminant formula is verified by the expansion force and rate of non load expansion of different dilated mudstones,and the results show that the expansive soil can be well judged.According to the disease situation in the actual project,the discriminant value of the expansive soil is divided.(4)All kinds of expansive soils are classified according to their expansibility.However,due to different environments,the expansibility of soil is also affected by water.Real time water content is different,it will affect its actually expansion state.Based on the discriminant study of swelling property of expansive soil,considering the external environmental factors of water,the swelling state of the expansive soil has been identified and classified by experimental research.