Numerical Modelling of Creep Behavior of Excavations Stabilized with Anchors with a Case Study in Tehran

Document Type : Research Article

Authors

School of Civil Engineering, University of Tehran, Tehran, Iran

Abstract

Some excavations need to be designed for a long time or sometimes they are left for a long time. Stabilization of most of the excavations has been done using anchors. Field surveys of these excavations show that in some cases, deformation of the excavations increases over time, and the locking force of anchors decreases, leading to dangers. Therefore, it is very important to know the long-term behavior of stabilization systems by an anchor and reduce the anchor load. The main purpose of this study is to evaluate the changes in anchor load in excavations. Numerical modeling of the long-term behavior of soils has many complexities and may not correspond to reality. Therefore, in this study, data on the long-term behavior of an excavation project in Tehran were collected and then numerical modeling in finite difference software was used to study the long-term behavior of this system. Also, using the back analysis method, the input creep variables of the rheological model of the time function in the numerical model were determined and used. Comparison of the results of this research and field survey results confirms the time function behavior of the numerical model performed in software. The results of this research show that in an anchor installed in the middle depth of the excavation project, a 7% reduction in load occurs one year after prestressing. Also, during the creep time, the maximum horizontal deformation of the excavation walls increases by 13% during one year.

Keywords

Main Subjects


[1] P. Sabatini, D. Pass, R. Bachus, Geotechnical engineering circular no. 4: Ground anchors and anchored systems, 1999.
[2] H. Ludwig, Short-term and long-term behavior of tiebacks anchored in clay,  (1984).
[3] R. Rezvani, M.A. Tutunchian, Horizontal displacement of urban deep excavated walls supported by multistrands anchors, steel piles, and in situ concrete piles: Case Study, International Journal of Geomechanics, 21(1) (2021) 05020008.
[4] M. Sanchez, J.-L. Briaud, S. Hurlebaus, M.M. Kharanaghi, G. Bi, Creep behavior of soil nail walls in high plasticity index (PI) soils: technical report, Texas A&M Transportation Institute, 2017.
[5] N.S. Montero-Cubillo, R.A. Galindo-Aires, A. Serrano-González, C. Olalla-Marañón, F.D. Simic-Sureda, Analytical model of an anchored wall in creep soils, International Journal of Geomechanics, 20(4) (2020) 04020027.
[6] R. Azami, Experimental Study of Soil Creep in Excavation Anchors, Tarbiat Modares university, 2017 ,(in persian).
[7] S. Mirzaee, Time effects in numerical analysis of excavation in urban areas, Bu-Ali Sina University, 2009 ,(in persian).
[8] A. Mahouti, Pull-out Behavior of Grouted Anchors in Marl, University of Tabriz, 2017,(in persian).
[9] T. Arayesh, Numerical Analysis of Viscoplastic Effect in Permanent Anchored Slope After along Time, Tarbiat Modares university, 2015 ,(in persian).
[10] A. Cheshomi, S.R. Ramezannejad Elyerdi, A. Fakher, Development of Tehran alluvium classification based on geological characteristics and geotechnical parameters, Scientific Quarterly Journal of Iranian Association of Engineering Geology, 11(1) (2018) 65-79.
[11] Y.-J. Lim, Three-dimensional nonlinear finite element analysis of tieback walls and of soil-nailed walls under piled bridge abutments, Texas A&M University, 1996.
[12] T. Schanz, P. Vermeer, P.G. Bonnier, The hardening soil model: formulation and verification, in:  Beyond 2000 in computational geotechnics, Routledge, 2019, pp. 281-296.
[13] Fast Lagrangian Analysis of Continua, in, Itasca Consulting Group, Minneapolis, 2019.
[14] S.M. Asadollahi, An Investigation Into The Stress Exerted To Facing Of Excavations Supported By Nailing And Anchorag, University of Tehran, 2017 ,(in persian).
[15] N. Yeganeh, A. Akhtarpour, J. Bolouri Bazaz, Parameters Determination of Soil-Anchor Interaction for Numerical Modelling According to Field Data, Modares Civil Engineering journal, 15(4) (2015) 105-116 ,(in persian).
[16] S.A. Sadrnejad, Soil plasticity and modeling, Khaje Nasir Toosi 2016 ,(in persian).
[17] R.E. Goodman, Introduction to rock mechanics, Wiley New York, 1989.
[18] L.-J. Su, J.-H. Yin, W.-H. Zhou, Influences of overburden pressure and soil dilation on soil nail pull-out resistance, Computers and Geotechnics, 37(4) (2010) 555-564.
[19] W.B. Wei, Y.M. Cheng, Soil nailed slope by strength reduction and limit equilibrium methods, Computers and Geotechnics, 37(5) (2010) 602-618.
[20] L. Li, M. Gamache, M. Aubertin, Parameter determination for nonlinear stress criteria using a simple regression tool, Canadian geotechnical journal, 37(6) (2000) 1332-1347.
[21] G. Gioda, L. Locatelli, Back analysis of the measurements performed during the excavation of a shallow tunnel in sand, International Journal for Numerical and Analytical Methods in Geomechanics, 23(13) (1999) 1407-1425.