The Influence Of Water Level Variation On Dynamic Performance And Cumulative Deformation Of Subgrade

The design life of subgrade in high-speed railway is one hundred years. The material properties of subgrade will be changed since rainfall and water level variation are difficult to avoid in the service life of subgrade, which result in the increasing of dynamic interaction of track structure-subgrade system and cumulative deformation. Furthermore, the running safety and comfort of train running and the design life of track structure will be reduced. As a most important factor to influence the alignment design and the operaiton maintenance, the influence of water level variation is considered in the design of high-speed railway.Theoretical analysis has limitations due to the complexity of train-rail-subgrade interation. At present, large-scale model test has been widely used for understanding the dynamic behavior of the track-subgrade of high-speed railway. The full-scale model test of high-speed subgrade proposed for Shanghai-Nanjing intercity high-speed railway line was firstly constructed at Zhejiang University which took the influence of water level variation into consideration. In order to study the influence of water level variation on dynamic performance of subgrade, model tests, numerical modeling of Abaqus and dynamic traxial test were carried out in this thesis. The main contents are as follows:(1) Model test consider the influence of water level variation on dynamic performance and cumulative deformation of subgrade were conducted. The test procedure involved two programs which were the water level rising and wetting-drying cycles of subgrade. Test contents including the dynamic soil pressure, velocity, elastic deformation and cumulative deformation of subgrade.(2) A three-dimensional model of Abaqus was established to simulate train-induced dynamic soil pressure in the subgrade. The method to calculate the degradation of dynamic stress with depth in the subgrade was put forward.(3) Based on the analysis of cumulative deformation, theoretical model of cumulative deformation were proposed. The model of cumulative deformation took the initial stress state, material properties and dynamic soil pressure into consideration. The material parameters were obtained by dynamic triaxial test.(4) At last, a series experiments were taken after the full-scale model test was accomplished, which was used to evaluate the performance of track structure and subgrade, including concrete base, CA mortar, foundation soil, subbase layer of subgrade, granular base layer of subgrade and foundation.