Optimization of Subgrade Structure Parameters of Ballasted Track Passenger Dedicated Line

In order to improve the force condition of ballasted railway subgrade structure and reduce maintenance cost, it is necessary to study the influence of subgrade structure parameters on subgrade dynamic response under train load. Orthogonal test was designed and used to analyze the sensitive relationship between dynamic response of railway subgrade structure and parameters of each structural layer, and the optimal parameter combination of subgrade structure of ballasted railway was determined by combining analytic hierarchy process (AHP) and linear evaluation index. The parameters include elastic modulus of ballast bed, elastic modulus of surface and bottom layer of subgrade bed, thickness of ballast bed, thickness of surface and bottom layer of subgrade bed, and elastic modulus of foundation. The results show that the thickness of track bed is the main factor that affects dynamic stress of ballast bed, dynamic stress and vibration acceleration of surface layer of subgrade bed. The elastic modulus of foundation is the main factor that affects the vertical displacement of the sleeper. The mechanical optimum parameter combination of ballast track structure parameters is determined as the elastic modulus ballast bed is 250 MPa, elastic moduli of surface and bottom layer of subgrade bed are 120 MPa and 115 MPa, the thickness of ballast bed is 0.35 m, the thickness of surface and bottom layer of subgrade bed are 1.1 m and 2.3 m, and the elastic modulus of foundation is 70 MPa