Investigation of the effect of building soil and shallow circular tunnel interaction on the seismic response of a 20-story SAC building

From a seismic geotechnical point of view, the effect of underground structures such as inner tunnels on the seismic response of the earth's surface and the surrounding environment has been revealed by researchers. In this paper ، considering the building-soil-tunnel system interaction ، the effect of shallow tunnel presence on the seismic response of the 20-story, SAC benchmark building is investigated. The building-soil-tunnel interaction system is modeled in two dimensions and considering the nonlinear behavior of soil materials using the equivalent linear method. 8 benchmark earthquake records have been used to evaluate the seismic performance of this building. In this study, the effect of horizontal and vertical tunnel distance, excitation frequency, and flexibility ratio, as well as site soil type on the seismic response of the building, has been investigated. The results show that for the sine wave, the maximum effect of acceleration magnification is observed in the horizontal distance ratio of 4, and by decreasing the dimensionless period ratio, the tunnel effect on the magnification increases due to the passage of waves with shorter wavelengths. Additionally, the maximum roof displacement and base acceleration for soil type IV are larger than type III and type III is larger than type II. Also, for soil type IV, the maximum amplification of roof displacement and base acceleration is 54 and 46 percent respectively.