Fundamentals of track lateral shift for high-speed rail applications

The fundamental mechanics of track lateral shift due to vehicle and thermally induced loads are defined, and an analytic approach is presented for the determination of "limit" loads and deflections on the track to prevent progressive lateral shift. The proposed approach consists of the coupled use of a comprehensive vehicle-track dynamic model to evaluate the lateral loads on the track, and a "dynamic" track lateral response model to determine the residual lateral\ndeflections under multiple load passes. The lateral response model is augmented by a track vertical deflection model for the determination of the "vertically loaded lateral resistance." The lateral response model simulates moving loads, and includes a nonlinear tie-ballast lateral resistance idealization. Results of baseline parametric studies accounting for the influences of lateral resistance, curvature, longitudinal force, and other vehicle and track parameters are given, "limiting" lateral to vertical load ratios (L/Vs) are identified, and stable and unstable regimes of track shift under high speed operating conditions are predicted. Prototype safety criteria for track shift mitigation are proposed based on net axle load (NAL/V) limits versus allowable lateral track displacements. This work is part of the US DOT/Federal Railroad Administration's research effort\nto develop the technical information required to establish safe operating practices for high speed tracks.\n