Dynamic transmission characteristics of stratum under curved metro driving

Abstract

Curved sections are common features of urban metro systems. Owing to limited construction space, the curve radius is often minimized. The excitation effects of trains on curved lines and the resulting stratum dynamic conduction differ from those on straight lines, necessitating specialized research on the horizontal dynamic conduction characteristics. This study utilized the Navier dynamic balance equation and Euler–Bernoulli curved beam theory to describe the dynamic systems of the stratum medium and buried subway structure, respectively. The dynamic conduction effect from a moving excitation point to the surface under a horizontal resonant load was analytically solved. The influences of the structural stiffness, and critical velocity of the conducting medium on the dynamic conduction characteristics of the stratum were explored. The results indicated that both the soil medium and its internal structure affected the critical velocity of the tunnel-stratum system. When the subway structure was modeled as a buried beam, the critical velocity of the formation would decrease, and the system would fluctuate when the load moving velocity exceeded this critical velocity. Under a harmonic load, damping reduced the dynamic conduction in the stratum, resulting in significantly lower response degrees at the surface compared to the load application points. Adding beam bodies limits the dynamic transmission to the surrounding soil, resulting in lower system response values compared to a beamless stratum. Harmonic loads compressed or elongated waves before and after crossing observation points, causing the stratum’s dynamic conduction waveform to conform to the Doppler effect principles. The changes in the stiffness of the embedded beam bodies altered the wave conduction velocities within the stratum, contributing to the dynamic receiving frequency to deviate from the predicted Doppler effect value.