Research On Settlement Characteristics And Numerical Simulation Of Unsaturated Soil Subgrade Of High-Speed Railway

In order to meet the high speed and comfort of high speed railway,subgrade settlement must be controlled in a certain range.The precise prediction of postconstruction settlement is one of the key techniques to ensure the quality of the highspeed railway construction project.The in-situ observation data show that the shapes of settlement vary greatly under different unsaturated conditions.Limitations and risks are observed to predict unsaturated settlement using the traditional predication methods based on the saturated theory.Therefore,it is of great value to study the consolidation and settlement problem based on unsaturated soil.Influence of suction on consolidation and settlement of unsaturated soils was studied by the test of unsaturated soil consolidation,in-site settlement monitoring theoretical analysis for Jinan-Qingdao high-speed railway.In addition,the theory of the Influence of permeability coefficient on consolidation was determined by multiphase calculation model.The theoretical basis and Experience reference of Settlement prediction of high speed railway subgrade were provided.The main content and research results are as follows.(1)The comprehensive laboratory consolidation tests under different matric suction,axial pressure,and dry density were conducted.The results show that the suction is the main factor for the characteristics of consolidation.When the matric suction is high and low the consolidation settlement time is faster,while the consolidation time is prolonged when the suction is in the middle value.The dry density and axial pressure are main factors for the deformation,while non-Influence on time of consolidation.(2)The high speed railway subgrade site settlement monitoring was conducted in Weifang where is unsaturated land area,and the results of the monitoring showed that there was a relatively long period of settlement in the area with relatively low saturation of the passenger railway from Zhengzhou to Xian and saturation of the WuhanGuangzhou High-speed railway.According to the characteristics of settlement curve and the low correlation coefficient,the Poisson curve,hyperbolic method,exponential curve method,three-point method and the unsaturated soil settlement prediction model based on VG model were compared.The concept of deviation degree and stability is proposed to evaluate the above methods.The results show that the unsaturated soil settlement prediction model based on VG model is safe and fit,and the prediction accuracy is higher.(3)The existing unsaturated multiphase finite element analysis method was applied for one-dimensional numerical calculation of unsaturated soil consolidation problem.Influence of suction on consolidation and settlement of unsaturated soils was confirmed by the result of numerical calculation.The critical factor of relationship between matrix suction and consolidation time is "?" shape distribution is permeability coefficient.Compared with the test data,the program has high applicability.