Fatigue Test And Simulation Analysis For Improved Soil Subgrade Under The Ballastless Tracks Of High-speed Railway

High-speed railway in China is in full development and construction stage,during which there are many problems and difficults.In roadbed construction,duing to the lack of A&B group fillers along the route,we usually make use of cutting spoil,which means a large number of improved weathered soil will be used to replace A&B group fillers to fill the subgrade.Currently there are no systematic researches on the dynamic properties and deformation characteristics of the roadbed, of different soil types, under dynamic loading. For the above, on the basis of comprehensive analysis of the currently situation of completely weathered granite,combined with related research projects of the Wuhan-Guangzhou Passenger Dedicated Railway, through theoretical analysis, field test and numerical simulation methods,we did a research in depth and widely on dynamic response of the completely decomposed granite improved soil subgrade under cyclic loading. The main research work of this dissertation gained can be summarized as below.(1)Demonstrated the scientific feasibility of fatigue test method in theory.(2) Established a three-dimensional dynamic finite element model, with careful consideration of the various parts of the roadbed, introduced a elastic-plastic creep model to calculate the dynamic response of the completely decomposed granite soil subgrade structure under the cyclic loading and got the law of dynamic response and vertical load transferring in subgrade.The dynamic finite element analysis of fatigue test showed that:â‘ The value of the dynamic response of completely decomposed granite soil subgrade is small,the dynamic stress of the surface of subgrade is between 69.9 kPa and 73.2kPa, the dynamic displacement is between 0.17mm and 0.38mm,which meets the dynamic values requirements of high-speed railway.â‘¡Cyclic loading did a great impact on the roadbed and the value of dynamic response decrease fast along the depth of the subgrade, the value is small when the depth is greater than 2.75m and the dynamic response has been close to 0 when the depth is 4.2m.â‘¢As the Cyclic loads changes cyclically, the dynamic response of subgrade changes like "N".(3)The field fatigue test showed that:â‘ The elastic-plastic cyclic creep model can be used to evaluate the cumulative plastic deformation characteristics of subgrade with improved completely weathered granite soil.â‘¡The completely decomposed granite improved soil can not be used to fill the subgrade immersed in water, and must strengthen measures of drain and waterproof.â‘¢The finite element model of completely decomposed granite improved soil subgrade is reliable and it can be used to do simulation and analysis during practical engineering.â‘£By comparing field test data with analysis results,it can be concluded that the completely decomposed granite improved soil can be used for high-speed railway, and it's of good stability under long-term cyclic loading, which fully meets the design specifications.