Numerical analysis of the dynamic response of a ballastless railway track rested on non-stabilized and cement-stabilized soft soil considering undrained conditions

Soft subgrade poses a significant design challenge for railway projects because of its high compressibility and low shear wave velocity. Therefore, it is important to increase its stiffness and strength to enhance the performance. Stabilizing the soil with cement is one of the most widely used methods for achieving the aforementioned goal. However, there is lack of studies on the application of the soil–cement stabilization on the performance of a ballastless railway track. This study examines the effect of stabilization of the soft soil by cement on the response of a ballastless railway track under static and moving X-2000 train loads. The three-dimensional finite element analysis has been used to achieve the goal of the research, where the modeling involved simulating the original and stabilized subgrade, the ballastless railway system, and the static and moving trains to allow realistic simulation of the problem under consideration. In addition, the non-stabilized soft soil (subgrade) has been modeled considering the undrained conditions. The results have been presented in terms of the dynamic settlement, the dynamic amplification factor (DAF), and the acceleration. It has been found that the maximum settlement of the railway track decreases by increasing the thickness of the stabilized subgrade layer. The maximum settlement decreases by a percentage ranging from 1 to 33% for stabilized layer thicknesses of 0.3 m to 3.0 m, respectively. Additionally, it has been found that the critical speed of the ballastless railway track system is unaffected by the presence of the stabilized layer. Furthermore, the dynamic amplification factor significantly decreases with the increase in stabilized layer thickness, demonstrating that stabilization performs better under moving loads than it does under static loads. Also, the vibration-induced moving train reaching nearby areas is not affected by the stabilization of the soft soil underneath the ballastless railway track. The findings of this work are useful to engineers conducting desk studies on the implications of various methods to stabilize soft soils for a ballastless railway design project.