Application of N37A Nonlinear Constitutive Relation in the Subgrade Filling of Ballastless Track
Abstract
As railway engineering moves toward a more severe environment, the service safety of track structure infrastructure needs more detailed control, and correct cognitive mechanical behavior of infrastructure has always been the difficulty and bottleneck of refined analysis of railway engineering. In this thesis, taking the stress–sensitive nonlinear constitutive of subgrade as a breakthrough, this thesis puts forward that the constitutive relationship that is self-consistent with material behavior is embedded in the finite element calculation model of subgrade, which provides a feasible method for fine analysis of railway engineering. In the study, the bottom layer of the subgrade bed for the Ballastless track is taken as the research object. The stress-related nonlinear constitutive relationship N37A is inserted into the subgrade material through a user-defined subroutine. Then, the material’s rebound modulus evolution parameters returned from the triaxial test are used to analyze the nonlinear base mechanical behavior of the embedded material. The following conclusions are obtained: (1) The N37A nonlinear model can capture the stress sensitivity of the material, and describe the mechanical behavior of the bottom layer of subgrade bed factually. (2) The deadweight has led to the nonlinear significant increase of the resilient modulus, and the train load causes the different development of the stress–strain response at different locations. (3) The resilient modulus of the bottom layer of the subgrade bed is small at the top surface but large at the bottom surface, which is monotonically increasing. With the loading of the train, the resilient modulus curve with different depths rotates approximately clockwise at the center about 0.75m away from the top surface of the bottom layer of the subgrade bed. (4) The value of resilient modulus at the top surface of the bottom layer of the subgrade bed is as the center line of the subgrade > under the rail > the edge of the base, and the bottom surface is just opposite. The relative difference in resilient modulus between them is less than 3MPa.
This paper was recommended by Regional Editor Takuro Sato.
