Abstract:

Based on Biot's dynamic poroelastic theory, a system of rail pad, sleeper, ballast and double layers of transversely isotropic saturated subgrade is proposed, in which the system can be decomposed as a track system and a double layered soil system. Applying the double Fourier transformation technique to the track system and the soil layer system, the governing equation of track-layered transversely isotropic saturated subgrade system is simplified as an eigenvalue problem for solving a 6 order governing equation. The solutions of the dynamic response of track system-double layered transversely isotropic saturated subgrade to train loads are derived in the transformation domain. Numerical results are obtained by using the inverse fast Fourier transform(IFFT); and then the IFFT are used to analyze the influence of the modulus and Poisson ratio of the first and the second layer of soil on the displacement, pore pressure and shear stress. It is shown that there are great influence of the stiffness of soil layers on the dynamic response; and the influence of modulus are greater than that of Poisson ratio. The computational results can serve as a reference for determination of the reinforcement depth in the soft subgrade.

Key words: train load, track system, transversely isotropy, saturated soil, dynamic response