Research Of Interaction Between The Subgrade Bed And The Ballast Bed On Existing Speed-Raising Railways

The problem exposed on the track structure of existing railways is found more and more serious with the increase of the train running speed . The differential remnants deformations of the subgrade and track structures appear under the repeated load , it change the geometrical dimension of the subgrade and track structures. So serious unevenness is prone to occur in the track structure,especially in the linking of structures of different engineering properties. The track irregularities has a close relationship with the consistency and stiffness of the subgrade and track structures.Therefore, this paper conducts systemic studies to the interaction between the subgrade bed and the ballast bed on existing Speed-Raising railways on the basis of consulting the relative domestic and overseas technical materials.This paper has comprehensively analyzed the interaction between the subgrade bed and the ballast bed through four kinds of research method such as theoretical analysis, numerical simulation, model test, investigation and engineering test in situ,and so on.1 , Dynamic Experimental Research of Interaction Between the Ballast Bedand the Subgrade Bed on Existing Speed-Raising Railways Under Cyclic loadingAiming at reasonable matching of parameters of the subgrade bed and ballast bed in speeding-up reconstruction of existing railways and design and construction of special high-speed lines for passenger traffic, a number of laboratory dynamic model tests were carried out with six groups of soil samples of varied compactness and the dynamic stresses, elastic deformations, plastic deformations and reaction moduli of the subgrade and track structures were measured. Through comparison among results of model tests under different compacting factors, the developing tendencies of elastic and plastic deformations and reaction moduli were revealed; the developing regularities of the foundation coefficients, compacting factors, and dynamic and static rigidities of the subgrade and track structures were explored. The critical values of the influences of the subgrade bed on the ballast bed were defined. When the compacted thickness of the subgrade bed was 0.93, the critical dynamic rigidity of the subgrade bed was 75 MPa/m, the critical dynamic elasticity deformation of the subgrade bed was 1.5 mm and the critical dynamic rigidity of the ballast bed was 110kN/mm. The study of the parameter matching and dynamic interaction between the subgrade and ballast beds is significant in guiding engineering practice.2, Dynamic Numerical Simulation Research of the Subgrade and Track StructuresThe numerical simulations of the interaction of the subgrade and track structures are made by finite difference software FLAC.The material parameters are gained by the inverse analysis method. It is found that the numerical simulations results and model test data have better consistency. The further researches of the model test plan...