Research on the Detection of Construction Defects in the SCC of a Ballastless Track Slab Based on the Fluctuation Characteristics of Vibration Energy Distribution

Abstract

Against the backdrop of China’s rapid high-speed railway development, ballastless track technology served as a core component of modern railway infrastructure. A critical construction challenge lay in the quality control of the self-compacting concrete (SCC) layer beneath prefabricated track slabs, where construction-induced defects such as bubbles and voids frequently occurred. These defects not only impede project delivery but also present significant risks to the long-term operational safety of high-speed railways. This study proposes a nondestructive testing (NDT) method for identifying such construction defects, leveraging the fluctuation characteristics of vibration energy distribution. The method integrated the energy operator and variational mode decomposition (VMD)-Hilbert transform to analyze the vibration response of track slabs, with a finite element model established to extract acceleration signals under various defect conditions. Through systematic analysis of vibration energy characteristics, including damping ratio, frequency band shift, and energy migration, the results demonstrate that defects increased the structural damping ratio and shifted the dominant energy of the acceleration signal from low to medium-high frequencies. Notably, distinct offset patterns in the fourth frequency band were observed for bubble and void defects, enabling effective defect classification. This study provided novel, reliable indicators for the NDT and health assessment of SCC layer defects in ballastless track systems.