STUDY ON STATIC AND DYNAMIC RESPONSE OF RAILWAY SLAB TRACK SYSTEMS STRUCTURES

Abstract

The advent of high-speed rail (HSR) has transformed the landscape of railway engineering, creating new demands for track systems that can reliably operate under very high speeds while maintaining safety, stability, and structural endurance. Conventional ballasted tracks, while cost-effective at the construction stage, are increasingly recognized as unsuitable for modern HSR due to ballast deterioration, uneven settlement, and limited resistance to dynamic loading. In response to these challenges, slab track systems have emerged as a superior alternative, providing enhanced stiffness, reduced deflection, better vibration performance, and longer service life. Countries such as Japan, Germany, France, and China have already integrated slab track technology extensively, demonstrating its advantages in high-speed applications. India is following this global trend through the Mumbai–Ahmedabad High-Speed Rail (MAHSR) project, its first dedicated HSR corridor. The implementation of precast slab tracks on such scale offers a significant opportunity to critically assess the static, dynamic, and fatigue behavior of these systems under diverse operational, climatic, and geotechnical conditions unique to the Indian context. This thesis, therefore, undertakes a comprehensive evaluation of the mechanical and durability performance of precast slab tracks, drawing upon the MAHSR configuration as a case reference. Finite element modelling (ANSYS) is employed to study the static performance of slab and ballast tracks under uniform loading, with results showing that slab tracks reduce deflection by nearly 45% due to greater flexural stiffness. Parametric studies reveal that increasing the stiffness of the Cement Asphalt Mortar (CAM) layer enhances stability by 16.7% while marginally increasing shear stress, whereas optimizing rail pad stiffness reduces rail deflections by about 20%. These findings highlight the significance of balancing geometric and material parameters to achieve both stability and durability. vii The dynamic responses of slab tracks are explored through advanced computational modelling. FEM-based vibration analysis demonstrates the role of anti-vibration slab mats in mitigating dynamic effects, with thickness, stiffness, and damping ratio shown to be decisive factors in reducing vibration amplitudes transmitted to the surrounding environment. To capture train–track interaction with greater fidelity, the Moving Element Method (MEM) is employed using a 26-degree-of-freedom multi-body vehicle model combined with nonlinear Hertzian wheel–rail contact. MEM simulations provide accurate and computationally efficient predictions of vehicle–track interactions, capturing the influence of train speed, track irregularities, subgrade stiffness, and damping properties. Together, these analyses establish the importance of vibration mitigation strategies in ensuring passenger comfort, track stability, and environmental protection. To assess long- term durability, the fatigue behavior of key components is examined through both laboratory and numerical approaches. Four-point bending fatigue tests on CAM specimens demonstrate a three-phase strain evolution pattern comprising an initial rapid increase, a steady expansion stage, and a final rapid failure while modulus degradation is observed in the range of 5.2–6.5 GPa across different stress levels. Stress–life (S–N) curves are developed to evaluate fatigue life under cyclic loading. Complementary finite element simulations extend the analysis to the precast concrete slab, where modal frequencies, transient stresses, and cumulative damage are identified as critical determinants of service life. By integrating static FEM analysis, dynamic simulations, and fatigue evaluation, this research provides a holistic framework for understanding and optimizing slab track systems. The findings validate the structural and operational superiority of slab tracks over conventional ballasted systems and establish clear design recommendations concerning slab thickness, CAM stiffness, rail pad optimization, and the inclusion of slab mats for vibration mitigation. Beyond demonstrating the suitability of slab tracks for the MAHSR project, the outcomes contribute significantly to the development of durable, cost- effective, and sustainable slab track systems for future high-speed railway corridors in India.