Underground tunnels with circular cross section nowadays have great application in the field of transportation. One of their most prominent uses is the subway, built with the help of tunnel boring machines (TBMs). The design of ground-surface structures in the far field is related to the horizontal component of the peak ground of acceleration. Therefore, in this study, we tried to change the frequency of the soil-tunnel system by changing the overburden depth, diameter, and lining thickness of the tunnel, as well as changes in the soil specification, and calculate the maximum acceleration of the ground’s surface in the presence of the tunnel. The relationship between the peak horizontal acceleration of the ground surface and the frequency of the soil-tunnel system will result in the production of a horizontal acceleration spectrum. The results show that the amplification of ground surface depends on the period of the soil-tunnel system, the characteristics of the model, and the status of the point studied at the ground surface relative to the tunnel. On the projection of the center of the tunnel on the surface of the ground, the presence of the tunnel, rarely, at a long period, is effective in amplifying the spectral acceleration. While moving away from the image of the center of the tunnel on the surface of the ground, the presence of the tunnel in many cases, in long periods, amplifies spectral acceleration. The presence of the tunnel amplifies the spectral acceleration on the ground surface above 11%, while the presence of a tunnel reduces the spectral acceleration on the ground surface by up to 15% (attenuation). Using Plaxis 2D and Ansys finite element software, the case study was conducted on a Delhi subway tunnel with horizontal components of acceleration records similar to the construction site.

In this study, the effect of urban subway tunnels with a circular cross section on the spectral velocity of the ground surface in alluvial soils was investigated. By changing the soil characteristics of the tunnel construction site and the geometric characteristics of the tunnel section (such as the radius and thickness of the lining and the depth of its placement), the frequency of the soil-tunnel system was changed. Then, the maximum velocity values were extracted for different parts of the ground surface. By averaging the data for each model, the amount of spectral velocity for different parts of the ground surface was extracted. The results show that the spectral velocity of the ground surface decreases by increasing the tunnel radius by 92% to a maximum of 12.3% in the tunnel center image on the ground’s surface. Also, by increasing the doubling of the depth of the tunnel, the spectral velocity of the ground surface at a distance approximately equal to the radius of the tunnel is reduced to a maximum of 4.42%. The increase in the spectral velocity of the ground surface due to the increase in the depth of the tunnel is a maximum of 12.13% and occurs at a distance approximately equal to the tunnel radius. In a small number of reviewed models, increasing the depth of the tunnel placement increases the spectral velocity of the ground around the tunnel. The effect of increasing the thickness of the tunnel lining on the spectral velocity of the ground surface was also investigated. In tunnels with greater overhead depth, the spectral velocity of the ground surface increases by a maximum of 10.86% with increasing thickness of the tunnel lining and occurs in the image of the center of the tunnel on the ground surface. In tunnels with less overhead depth, the spectral velocity of the ground surface decreases by a maximum of 7.56% with increasing thickness of the tunnel lining and occurs approximately at a distance equal to the diameter of the tunnel from the image of the tunnel center to the ground surface. The study was performed using PLAXIS 2D and Ansys finite element software.