Influence Of Subway Station On The Ground Motion

In recent years, the underground space is developed and utilized in large scale. The typical large transportation equipment—the subway has become the main transportation vehicle of some cities. Therefore, to study the influence of underground tunnel on earthquake motion is important both in engineering and practice. Flush, which is a complicated finite element analysis program, is used in this paper, and the object investigated expands from homogeneous site to layer site which can better reflect the real situation, and the influence of linear and nonlinear situation of site with tunnel on ground motion is studied.It is found in this research that, on the surface near the tunnel, under the linear situation, the amplification effect of site with tunnel on earthquake motion is less than the one of corresponding free field,and the response spectrum shapes of vertical acceleration at different surface points are different. Besides, the predominant period of vertical acceleration response spectrum is less than the one of horizontal acceleration response spectrum, which indicates that the radio-frequency component of vertical acceleration is relatively more.The equivalent linearization method is used in this paper to study the influence of earth mass nonlinearity on earthquake motion. It is founded that they have similar law, but the acceleration response spectrum peak values in horizontal and vertical direction in nonlinear situation are much less than the values in linear situation. Compared to the homogeneous linear site with tunnel, the predominant period of the nonlinear one is longer. This shows the nonlinear case the tunnel of the relatively long period of seismic wave amplification significantly higher than the linear case. The influence law of tunnels in homogeneous site and layer site on earthquake motion are basically identical.In addition, the amplification effect of tunnel with concrete lining on earthquake motion is less than the one of free field, while the amplification effect of tunnel without concrete lining on earthquake motion is either bigger or less than the one of free field. Both of them show changes according to certain rules with the change of surface point, which indicates that the concrete lining has a big influence on the model with tunnel. However, according to the results of both, the corresponding period of horizontal acceleration response spectrum peak value is similar with the site predominant period, which represents that the earthquake motion response is mainly relevant with the site predominant period.