Numerical Simulation of the Stress–Strain State of a Railway Subgrade with Sub-Ballast of Hot-Mix Asphalt

This article provides a detailed analysis of ballasted and ballastless railway subgrade structures. The advantages and disadvantages of each structure are identified, and a solution is given for the use of an alternative option—application of sub-ballast with Hot-Mix Asphalt (HMA). The purpose of this study is to determine the strength and deformability parameters of the reinforced subgrade based on the results of numerical simulation of the stress–strain state. Based on the real parameters of the subgrade, a finite element model with sub-ballast is created. It is determined that the maximum value of the vertical displacement of the structure without sub-ballast is 12.5% greater than that of the option with sub-ballast. It is found that the sub-ballast blocks the ingress of a more stressed field into the subgrade and redistributes the vertical stresses. Accordingly, the obtained maximum stress in the middle of the sub-ballast does not cause even local failure in it. Experimental studies of HMA specimens under uniaxial compression conditions were conducted. The experimental results confirm the results of numerical simulation of the subgrade and prove that HMA in the sub-ballast clearly works in the elastic stage, effectively reducing the stresses (in percentage terms, 38.8 … 72.3%).