Seismic response analysis of long shield tunnels under non-uniform excitation

The numerical simulation method is used to study the seismic response of the soil-tunnel system under non-uniform excitation. The aim is to explore the response laws of the underground structures under non-uniform excitation and its difference with those under uniform excitation. First, based on the coherence function, power spectrum function and envelope function, the multi-point correlation artificial seismic synthesis is carried out, and the rationality of the synthesized artificial waves is verified by comparing with the target power spectra. Then, the generated seismic waves are batch-processed to obtain artificial seismic waves that can be used for calculation, including four kinds of waves, such as uniform waves, traveling waves, coherent waves, and coherent traveling waves. Taking a refined long shield tunnel model as the research object, the four kinds of waves are input respectively according to the unit at the bottom of the model, and the seismic response of tunnel structure and soil is calculated and analyzed. Based on the comparative analysis, the response of the ground and the tunnel under non-uniform excitation is smaller than that under the uniform waves when the longitudinal distance is small, but the peak acceleration response increases with the longitudinal distance and exceeds the response under uniform excitation. In frequency domain, the amplitude of the dominant frequency under the non-uniform excitation is reduced compared to that of the uniform waves, and the corresponding amplitude of the right frequency band of the dominant frequency increases. In addition, the non-uniform excitation will cause greater relative displacement of the linings and transverse plates in the tunnel cross-section. The influence of coherent waves and coherent traveling waves is greater, and more significant spatial variability is exhibited. Therefore, when conducting large-scale seismic simulation calculations, due consideration should be given to the spatial effects of ground motion.