考虑下卧弹性基岩的地下结构抗震分析模型

The widely used vibration analysis model can only consider the condition of the underlying rigid bedrock. On the basis of the equivalent node force method for seismic wave input and the repeatable boundary, a seismic analysis model of underground structure for the general one⁃dimensional SV wave propagating vertically upward problem was proposed in this paper. The model can take into account the effect of elastic base, namely both the restoring force of elastic base and the dissipation of seismic waves outward. The viscous⁃spring boundary and the corresponding equivalent node force formulation were introduced. The repeatable boundary was validated with a numerical example as well. With elastic homogeneous and layered ground cases, the accuracy of the analysis model was verified by providing comparisons between its results and analytical solutions. Taking Shanghai layered ground as an example, the comparison analysis between the vibration method only considering rigid base condition and the analysis model in this paper was conducted. Both free field response and the internal force response of tunnel structure from the analysis in this paper are consistent with those from vibration model at the beginning, but there are significant differences in the later stage because the difference between elastic base and rigid base. The analysis model in the paper is in line with the actual situation for seismic analysis of underground structures with elastic bases condition.