Shaking Table Tests of Underground Substation Considering Soil–Structure–Equipment Interaction

To investigate the seismic dynamic response characteristics of underground substations, considering the interaction among soil, structure, and equipment, a model soil field shaking table test with a similarity ratio of 1:25 was conducted. Detailed analysis was conducted on the acceleration amplification factors, Fourier amplitude spectra, and displacements of soil, structure, and equipment during the experimental process. The experimental study revealed the following findings: It was concluded that the seismic excitation had a significant impact on the acceleration response of equipment near the edges of the structure, demonstrating an amplification effect. Both the acceleration amplification factors of the station structure and the site generally decreased with increasing input seismic intensity. As the seismic intensity increased, this decreasing trend gradually weakened. Additionally, the peak values of acceleration Fourier spectra often decrease with increasing burial depth. The examination of the postearthquake model system revealed the presence of surface cracks in the soil, which exhibited varying degrees of severity. These cracks were observed both parallel and perpendicular to the direction of excitation, with a significant concentration of soil fissures occurring directly above the structural elements.