چكيده به لاتين
It has been observed for years that the role of site effects in intensifying ground vibrations is evident. Local site conditions affect all critical characteristics of strong ground motion, including amplitude, frequency content, and duration of the noticeable earthquake effects. Furthermore, considering previous research on the impact of underground structures (tunnels) in a soil layer, the current study investigates the issue regarding the effects of underground structures (tunnels) on a two-layer soil response to ground shaking, using physical modeling with a shake table. In the conducted experiments using a shaking table, a polyethylene pipe with specific dimensions and size, along with validated scaling factors, was used to simulate a tunnel. Additionally, by placing it in a box with specified sandy soil, the seismic response of the tunnel in a layered soil has been investigated on the Earth's surface. Furthermore, the effects of the foundation (surface structure) and the two-layered soil on the acceleration and foundation response have been studied. As a result, according to the results obtained in the acceleration of 0.1 g in both unloaded and loaded conditions, the acceleration increases with a gentle slope from the rocky surface towards the ground surface, and we witness the magnification of acceleration.According to the results presented, the presence of a surface structure has had an impact on reducing surface acceleration amplification, and this reduction has been observed by passing through the tunnel and changing the soil type. Considering the characteristics of the second-layer soil, we are witnessing a decrease in surface acceleration. In acceleration 0.2 g, similar to acceleration 0.1 g, we observe an increase in acceleration from the ground to the surface, as well as an adverse effect of superficial presence on the reduction of magnification of high tunnel acceleration compared to free space. In acceleration, 0.28g, the presence of the superficial causes a reduction in acceleration magnification, and with an increase in frequency, we observe a decrease in the slope of magnification. Finally, to investigate and analyze the effect of the tunnel and the two soil layers in simulating uniformity, we have compared the results of this study with the results of the research by Bazyar and Dehghani in 2021, who examined the effect of the tunnel in a single soil layer. It is worth mentioning that the experiments conducted by me were carried out simultaneously with two other experiments on a shake table with different subjects and material specifications at Amir Kabir University..
