Over the past two years, Transportation Technology Center, Inc. (TTCI) has been investigating how tie and ballast parameters affect lateral track strength after surfacing. This investigation included both a literature review of previous work in the United States and single tie push tests (STPTs) performed under a variety of tie and ballast conditions at the Facility for Accelerated Service Testing (FAST) in Pueblo, CO. Knowing which parameters affect lateral tie strength and comparing the influence of the various parameters can help in lateral stability risk-assessments in continuously welded rail (CWR) track.
The results of both the literature review and the STPT testing showed that the parameters of post-surfacing tonnage accumulation (for ballast density), tie type, ballast shoulder width, ballast crib height, tamping lift height, and ballast particle characteristics all have a significant influence on the lateral tie strength of clean ballast. The results both emphasize the importance of considering multiple parameters when assessing track buckling risk and verifies the good practice of having both full ballast shoulders and crib heights for resisting lateral and longitudinal movements. TTCI plans to incorporate these parameters into mathematical models that predict the lateral tie strength based on measurable tie and ballast condition parameters, holistic track buckling prediction models, and risk-based rail neutral temperature (RNT) management recommendations.