Seismic behaviour of circular tunnels accounting for above ground structures interaction effects |
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| Affiliation: | 1. Aristotle University of Thessaloniki, Research Unit of Soil Dynamics and Geotechnical Earthquake Engineering, Department of Civil Engineering, PO Box 424, GR-54124 Thessaloniki, Greece;2. University of Catania, Department of Civil and Environmental Engineering, Sicily, Italy;1. Aristotle University of Thessaloniki, Department of Civil Engineering, Thessaloniki, Greece;2. University of Cambridge, Schofield Centre, Cambridge, UK;1. Department of Civil Engineering, Zanjan Branch, Islamic Azad University, Zanjan, Iran;2. Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), No. 26, Arghavan Street, North Dibajee, Farmanieh, Tehran, Iran;3. Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;1. Institute of Geotechnical and Underground Engineering, Beijing University of Technology, Beijing, China;2. School of Civil and Transportation Engineering, Beijing University of Civil Engineering and Architecture, Beijing, China;1. College of Civil Engineering, Hunan University, Changsha, Hunan 410082, PR China;2. Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, MI 49931, USA;3. Department of Civil Engineering, University of Southern California, Los Angeles, CA 90089-2531, USA |
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| Abstract: | Tunnels are commonly designed under seismic loading assuming “free field conditions”. However, in urban areas these structures pass beneath buildings, often high-rise ones, or are located close to them. During seismic excitation, above ground structures may cause complex interaction effects with the tunnel, altering its seismic response compared to the “free field conditions” case. The paper summarizes an attempt to identify and understand these interaction effects, focusing on the tunnel response. The problem is investigated in the transversal direction, by means of full dynamic time history analyses. Two structural configurations are studied and compared to the free field conditions case, consisting of one or two above ground structures, located over a circular tunnel. Above ground structures are modeled in a simplified way as equivalent single-degree of freedom oscillators, with proper mechanical properties. Several parameters that are significantly affecting the phenomenon are accounted for in this parametric study, namely the soil to tunnel relative flexibility, the tunnel dimensions, the tunnel burial depth and the soil properties and nonlinearities during shaking. Tunnels response characteristics are compared and discussed, in terms of acceleration, deformations and lining dynamic internal forces. Internal forces are also evaluated with analytical closed form solutions, commonly used in preliminary stages of design, and compared with the numerical predictions. The results indicate that the presence of the above ground structures may have a significant effect on the seismic response of the tunnel, especially when the latter is stiff and located in shallow depths. |
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| Keywords: | Circular tunnels Seismic behavior Above ground structures–soil–tunnel dynamic interaction Dynamic analysis |
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