An Overview of Single-Objective Optimization Models for Assessing the Performance of Railway Ballast Under Cyclic Loading

The performance of railway ballast under repeated loading greatly influences the overall stability and durability of the track. It is mainly quantified in terms of induced plastic strain, resilient modulus, and ballast breakage index. Past laboratory and field investigations indicated that external loading conditions and intrinsic material properties of ballast such as coefficient of uniformity and mean particle size affect the deformations of ballast. Threshold ranges for geotechnical design parameters such as confining pressure, frequency, and ballast gradation are available in literature to optimize the service life of the ballast under cyclic loads mimicking actual field conditions. However, the proposed optimum range cannot be widely adopted for all the scenarios because every optimization model has constraints. Moreover, majority of the proposed empirical relationships developed to quantify the extent of ballast degradation were mostly derived from single-objective optimization studies. Therefore, this paper presents a comprehensive review of the existing single-objective models for predicting different ballast performance metrics. The relative advantages and shortcomings are discussed with their constraints for application to field problems.