چكيده به لاتين
Today, tunnels are widely used in urban infrastructure; Therefore, one of the existing concerns about tunnels is their stability and behavior in an earthquake. In the past, it was assumed that tunnels are not vulnerable to earthquakes; Because by reviewing the historical cases, it can be seen that their failure rate is lower than the Rosmine structures. However, in recent earthquakes such as the 1995 Kobe earthquake in Japan, the 1995 Chichi earthquake in Taiwan, and the 1999 Kojaeli earthquake in Turkey, underground structures suffered major damages. Therefore, we understand the importance and necessity of paying attention to earthquakes and seismic design of tunnels. In this research, a two-dimensional numerical modeling with nonlinear behavior and finite element method of a shallow rectangular tunnel was performed with OpenSees. The purpose of this research is to investigate the mechanical stresses of the tunnel wall due to the earthquake. This modeling was based on a large-scale shake table test with dimensions of 7 meters long, 3 meters wide, and 5 meters high, conducted by Elgamal et. al. it was compared and validated with the shaking table test results. Based on the analysis performed on the results with seismic excitation of Northrige earthquake, a very good match was observed between the recorded pattern of the acceleration on the soil surface, the acceleration on the tunnel, the bending moment of the tunnel wall and the stress-strain of the soil adjacent to the tunnel. although in some cases there was a slight difference compared to the shaking table test. Finally in a probabilistic analysis the effect of variability in the soil friction angle, the predominant period of the input loading wave and the maximum amplitude (PGA) of the loading sine wave acceleration are studied. Based on the obtained results, changes in loading and soil characteristics can cause up to 500% change in bending moment and magnification values. It was also found that the applied seismic loading variability has a more significant effect on the tunnel response and will more likely lead to the production of larger values of magnification and bending moment. These issues prove the importance of probability studies for investigating geotechnical problems and corresponding designs.
