Experimental Study on SAFETY Estimation of Subgrade Modulus of In-Service Ballasted Tracks in KOREA

The subgrade modulus is an important parameter in the railway safety and the analysis of the behavior of a ballasted track. However, because such analyses often use the design subgrade moduli, their results seldom agree with those of finite element(FE) analyses, which use the theoretically determined subgrade moduli. Moreover, it is difficult to experimentally determine the subgrade modulus and spring stiffness of an in-service track because track components such as the ballast, sleepers, and rails are installed over the subgrade. In this study, the subgrade modulus of an in-service ballasted track was estimated by measuring the dynamic response of the track for railway safety. The subgrade modulus was further predicted from a proposed subgrade modulus map developed from the results of field tests and empirical equations for comparison with the design value. The rail displacement of the ballasted track was also predicted by an FE model that considers the spring stiffness at the rail support point, which includes the subgrade stiffness. It was confirmed that the subgrade modulus of an in-service ballasted track could be reliably predicted on the basis of the dynamic wheel load and rail displacement using the proposed subgrade modulus map.