A Durability Test Study On Subgrade Structure Under Dynamic Load Of Train

In recent years, the high-speed railway with its high speed, low energy consumption, large capacity, light pollution, less land, and many comprehensive advantages such as safe and comfortable, has been the attention of the countries all over the world, and gained rapid development. But with the constant improvement of the circuit use fixed number of year, followed by the durability of the subgrade structure also increasingly prominent, it will threaten the security and stability of railway operation. Subgrade structure durability research, however, our country still lack enough theoretical research and engineering practice. Based on a brief review of the high-speed railway technology development at home and abroad and the roadbed dynamics theory and the experimental study on the history and present situation, on the basis of the definition of the durability of concrete structure, the durability of the structure of subgrade were studied. In the form of laboratory model test of subgrade structure durability problems are discussed in this paper, mainly made the following several aspects of the research results and conclusions.(1) Through the high-speed railway field test,the dynamic similarity principle, the type of constitutive relation of soil and simulation of train loads, from various angles of subgrade structure durability test method adopted by the scientific nature and feasibility of the analysis, to ensure the selected parameters are reasonable.(2) Through different loading amplitude of long-term cyclic loading fatigue test it is concluded that the structure of the subgrade surface dynamic stress and dynamic stress in subgrade structure along the depth of the subgrade and the width direction attenuation law and the change of dynamic stress with the load times. Increase subgrade height, foundation treatment, to strengthen subgrade of waterproof and drainage work helps to reduce the influence of dynamic stress on bed bottom structure.(3) Through different loading amplitude of long-term cyclic loading fatigue test it is concluded that the scope of the structure of the subgrade settlement. The settlement of subgrade structure are analyzed, the direction along the depth of the subgrade and the width direction distribution, and the rule of change with load number. Strengthen the bed in the following sections of material strength, reasonable foundation treatment and waterproof and drainage engineering helps subsidence control, to keep the line safe operation.(4) Through the triaxial test of subgrade filling after loading, it is concluded that the Shear strength changing rule of Cement Improved Loess from the subgrade mid-line and road shoulders and also analyzed the changes of loess foundation part of shear strength, provide a reference for the design and construction of ballastless track(5) Through the plate loading test of subgrade structure,it is concluded that the change of the stiffness and bearing capacity of subgrade structure under cyclic load, and the reason is analyzed.(6) Based on the fatigue test, some problems which need more study are presented.