Department of Civil Engineering, Faculty of Engineering, Yasouj University, Yasouj, Iran
Abstract
According to increasing demand of box-shaped tunnels in transportation networks, which are mainly built as cut and cover tunnels, the impact of natural hazards such as earthquakes on these geotechnical structures and seismic load reduction methods of these types of structures is more important than before. Nowadays, the use of lightweight materials such as geofoam plays fundamental role in civil engineering and has solved many of the challenges of civil engineering. In the present study, the role of geofoam materials as embankments for cut and cover tunnels on the internal forces of the tunnel structure during the earthquake have been investigated. The numerical modeling was performed by two-dimensional finite difference software, FLAC 2D v7.0. The results of an experimental study were used to verify the numerical model. Time histories of acceleration and bending moments for Kobe and Northridge earthquakes were examined. Based on the analysis, it was observed that the software was able to predict the results of the centrifugal experiment well and provided reliable results. EPS19 has been used as a geofoam embankment in the analyzes. The acceleration time history of the Kobe and Northridge earthquakes with a maximum acceleration of 0.3 g has been used in the analysis. In the numerical model of the present study, the equivalent linear model (ELM) has been used to model the behavior of the geofoam. Mohr-Coulomb elastoplastic model was used in soil behavior modeling for static analysis. The behavior of the soil in dynamic analyses was considered as nonlinear and modeled with hysteretic damping. The results are determined in the form of bending moment and shear force diagrams for the roof and wall of the tunnel. The diagrams were provided for static and seismic loading conditions. According to the results of numerical studies, it was observed that the geofoam model has a very good performance in reducing the bending moments and shear forces in static and seismic conditions. Present study shows that geofoam, as the cover material of the cut and cover tunnel, is able to reduce internal forces of the tunnel structure in static, seismic loading condition compared to the soil. Based on the results, it was concluded that geofoam is a suitable material for retrofitting the cut and cover tunnels during earthquakes.
Owen, G.N. and Scholl, R.E. (1981) Earthquake Engineering of Large Underground Structures. Report no. FHWA/RD-80/195, Federal Highway Administration and National Science Foundation, 279.
Salemi, A., Salemi, A. and Salehi, A.F. (2009) Analysis and design of lining of a cut and cover tunnel with rectangular section. (Case study: Line 1 Tabriz subway). 8th Tunnel Conference, Tarbiat Modaress University (in Persian).
Maugeri, M. and Soccodato, C. (2014) Earthquake Geotechnial Engineering Design. Chapter: 11. Publisher: Springer International Publishing, Editors: 279-340.
Park, D., Lee, T.H. and Kim, J.M. (2015) Damage states of cut-and-cover tunnels under seismic excitation. 6th International Conference on Earthquake Geotechnical Engineering.
Lee, T.H., Park, D., Nguyen, D.D. and Park, J.S. (2015) Damage Analysis of Cut-and-Cover Tunnel Structures Under Seismic Loading. Springer Science+Business Media Dordrecht.
Zarnani, S. and Bathurst, R.J. (2010) Numerical parametric study of geofoam seismic buffers with different. Constitutive models. 9th International Conference on Geosynthetics, Brazil.
Wang, D. (2011) Seismic Isolation Effect of a Tunnel Covered with Expanded Polystrene Geofoam. Advanced Materials Research Vols. 1943-1946.
Kiryu, S., Yoshitaka, M. and Hitoshi, M. (2012) Seismic response of a cut-and-cover tunnel isolated by polymer material. Earthquake Engineering & Structural Dynamics, 2043-2057.
Baziar, M.H., Rabeti Moghadam, M., Kim, D.S. and Choo, Y.W. (2014) Effect of underground tunnel on the ground surface acceleration. Tunnelling and Underground Space Technology, 44, 10â22.
Baziar, M.H., Rabeti Moghadam, M., Dong-Soo, K. and Choo, Y.W. (2015) Effect of Underground Structure on PGA at Ground Surface Considering Linear and Nonlinear Behavior for the Soil. JCME, 34(1), 119-137 (in Persian).
BASF (1997( Styropor Technical Information CD-ROM. Ludwigshafen, Germany.
Zarnani, S. and Bathurst, R.J. (2009) Numerical modeling of EPS seismic buffer shaking table tests. Geotextiles and Geomembranes, 26(5), 371-383.
Athanasopoulos, G.A., Pelekis, P.C. and Xenaki, V.C. (1999) Dynamic properties of EPS geofoam an experimental investigation. Geosynthetics International, 6(3), 171â94.
Athanasopoulos, G.A., Nikolopoulou, C.P., Xenaki, V.C. and Stathopoulou, V.D. (2007) Reducing the seismic earth pressure on retaining walls by EPS geofoam buffersâ numerical parametric study. In: CD, Proceedings of 2007 Geosynthetics Conference, Washington, D.C., USA, 15.
Ossa, A. and Romo, M.P. (2011) Dynamic characterization of EPS geofoam. Geotext Geomembrane, 29(1), 40-50.
Shadabi, S., Rabeti Moghadam, M., Parvizi, M., & Zamani Lenjani, M. (2020). Numerical Investigation of Geofoam Effect on the Internal Forces of Cut and Cover Tunnels during Earthquakes. Bulletin of Earthquake Science and Engineering, 7(2), 67-78.
MLA
Sadri Shadabi; Masoud Rabeti Moghadam; Mansour Parvizi; Mahdi Zamani Lenjani. "Numerical Investigation of Geofoam Effect on the Internal Forces of Cut and Cover Tunnels during Earthquakes". Bulletin of Earthquake Science and Engineering, 7, 2, 2020, 67-78.
HARVARD
Shadabi, S., Rabeti Moghadam, M., Parvizi, M., Zamani Lenjani, M. (2020). 'Numerical Investigation of Geofoam Effect on the Internal Forces of Cut and Cover Tunnels during Earthquakes', Bulletin of Earthquake Science and Engineering, 7(2), pp. 67-78.
VANCOUVER
Shadabi, S., Rabeti Moghadam, M., Parvizi, M., Zamani Lenjani, M. Numerical Investigation of Geofoam Effect on the Internal Forces of Cut and Cover Tunnels during Earthquakes. Bulletin of Earthquake Science and Engineering, 2020; 7(2): 67-78.
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