تعیین عملکرد رفتار دینامیکی دیوارهای خاکی میخ گذاری شده تحت بارگذاری‌های لرزه‌ای بر اساس تغییر مکان

نوع مقاله : Articles

نویسندگان

1 بخش ژئوتکنیک و زیرساخت، مرکز تحقیقات راه، مسکن و شهرسازی، تهران، ایران

2 دانشکده فنی و مهندسی، دانشگاه آزاد اسلامی، واحد تهران مرکز، تهران، ایران

چکیده

با توجه به گسترش روزافزون بهره‌وری از فضاهای زیرسطحی، نیاز بشر به پایدارسازی در زمان حفر و گودبرداری بیش ‌از پیش قوت ‌می‌گیرد. پایدارسازی و بررسی این روش در حالت دینامیکی به دلیل بهره‌مندی در سازه‌ها‌ی دائمی نظیر پایداری شیب کناره راه از اهمیت بالایی برخوردار است. یکی از روش‌های پایدارسازی دیواره‌های گود استفاده از روش میخ‌گذاری ‌است. لذا در این مقاله رفتار پایدارسازی‌ دیوارهای میخ‌گذاری شده دائمی تحت بار دینامیکی مورد بحث و بررسی قرار گرفته است. به کمک ابزارگذاری‌ها‌ی صورت گرفته در گود هتل نرگس شماره 2 و مدل‌سازی آن با استفاده از نرم‌افزار FLAC صحت این نرم‌افزار مورد تأیید قرار گرفت. سپس با در نظر گرفتن 15 نگاشت و ساختگاه‌های نوع 1، 2 و 3 بر اساس آیین‌نامه 2800، بارهای هارمونیک معادل محاسبه شده و تحلیل‌های دینامیکی برای چهار بار هارمونیک معادل، سه ساختگاه و سه ارتفاع مختلف 3، 6 و 9 متر و در دو زاویه مختلف میخ‌گذاری انجام شد. برای این منظور با در نظر گرفتن تغییر شکل لبه بالایی دیواره به‌عنوان معیار مقایسه بین تحلیل‌ها، مقادیر تغییر مکان در 72 حالت مختلف مشخص شد. بررسی نتایج تحلیل‌های فوق نشان داد که، با کاهش مشخصه‌های مقاومتی ساختگاه (از نوع 1 به 3) جابه‌جایی افقی لبه گود و پوسته نما افزایش یافته و با کاهش زاویه میخ‌ها جابه‌جایی افقی لبه گود و پوسته نما کاهش می‌یابد.

کلیدواژه‌ها


عنوان مقاله [English]

Determination of the Dynamic Behavior of Soil Nailed Walls Based on Displacement

نویسندگان [English]

  • Iraj Rahmani 1
  • Amir Nejati 2
1 Department of Geotechnical Engineering, Road, Housing and Urban Development Research Center (BHRC), Tehran, Iran
2 Faculty of Engineering, Islamic Azad University Central Tehran Branch, Tehran, Iran
چکیده [English]

Demand for high-rise buildings and shopping malls has increased in recent years. For this reason, these buildings have a variety of basements. Due to insufficient land, some parts of these structures are being built underground. Stabilizing vertical cuts by emerging methods provides a new way for the construction industry. In addition, the demand for stabilizing vertical cuts on highways and railways against dynamic forces has been raised. There are various methods for stabilizing underground cuts. Soil nailing is one of the most common methods for stabilizing cut slopes in building industry. In this method, the soil is strengthened by placing the steel rods into the drilled holes on the wall and the ground. It is worth mentioning that, this method could be used for underground construction. Whereas soil nailing wall system needs less space in comparison with other retaining wall systems, in urban areas especially where walls cuts are surrounded by structures is more applicable. Observations of the performance of soil nails walls in recent earthquakes indicate that their destruction by deep excavations rarely occurs. Literature review on the soil nail walls shows that the mechanism of reinforcement and design of the soil nail walls is without considering of seismic loading. However, few studies have been performed on the seismic behavior of these walls. In this paper, the dynamic behavior of the steel soil nail walls has been investigated numerically. In order to validate two-dimensional, nonlinear finite difference model created by FLAC software, obtained results from the instrumental excavation wall (Hotel Narges No.2) were used. In this study, a numerical parametric study was performed to investigate the factors affecting the behavior of the soil nail wall system. This parametric study has the effect of wall height (3, 6 and 9 m), nail angle (10 and 15 degrees), soil properties (type 1 to 3 based on Iranian code of practice for seismic resistant design of building (2800)) and seismic loading characteristics such as magnitude, frequency of the maximum acceleration of the earth's surface were examined. In addition, four equivalent harmonic loads instead of 15 time history are used. After analyzing 72 different models, it was concluded that by decreasing the soil shear strength (types 1 to 3), the displacement of the upper edge of the wall would increase sharply, with the decrease of the nail angle (from 15 to 10) horizontal displacement of the upper edge wall reduced. By decreasing the angle of the nails (from 15 to 10), the force of the nails is increased. Increasing the height of the wall increases the horizontal displacement of the upper edge of the wall. Also by changing the type of harmonic loading type 1 to type 4, the behavior of the soil nail wall varies with soil type changes, which can be attributed to the effect of soil damping and soil type on the different seismic behavior of the nailed structures. The calculated dynamic analysis results show that the data are scattered under four different harmonic loads. Therefore, the seismic performance of the soil nail structures depends on the geometry parameters and the selection of the main mapping parameters including mold period, acceleration, and mapping duration is very important and requires sufficient accuracy. The dominant mode of deformation of the soil nail wall for four harmonic loads, and for all heights is around the intersection point of the wall and cavity.

کلیدواژه‌ها [English]

  • Soil Nail Wall
  • Reinforced Soil Structure
  • Dynamic Behavior
  • Finite Difference Analysis
  1. Lazarte, C.A., Elias, V., Espinoza, R.D., Sabatini, P.J. (2003) Geotechnical Engineering Circular No. 7, Soil Nail Walls. Federal Highway Administration (FHWA), Report No. FHWA0-IF-03-017. Washington, DC., USA.
  2. Mononobe, N. and Matsuo, H. (1929) On the Determination of Earth Pressure during Earthquakes, Proceedings, World Eng. Conference, 9, 176.
  3. Okabe, S. (1926) General Theory of Earth Pressure. Journal of the Japanese Society of Civil Engineers, Tokyo, Japan, 12(1).
  4. Pedley, M.J. (1992) Ground modification on soil and rock anchorage, rock bolting, soil nailing and dowelling. Soil Nailing Lecture Notes on Ground Modification Seminar, University of Technology, Sydney, 51–89.
  5. Davis, M.C.R., Jacob, C.D., and Bridle, R.J. (1993) An Experimental Investigation of Soil Nailing Retaining Structures. Thomas Telford, London.
  6. Turner, J.P. and Jensen, W.G. (2005) Landslide stabilization using soil nail and mechanically stabilized earth walls: case study. Journal of Geotechnical and Geoenvironmental Engineering, 131(2), 141–150.
  7. Li, J., Tham, L.G., Junaideen, S.M., Yue, Z.Q., and Lee, C.F. (2008) Loose fill slope stabilization with soil nails: full-scale test. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 134(3), 277-288.
  8. Ehrlich, M., and Silva, R.C. (2015) Behavior of a 31 m high excavation supported by anchoring and nailing in residual soil of gneiss. Engineering Geology, 191, 48-60.
  9. Gutierrez, V., and Tatsuoka, A.F. (1988) Role of facing in reinforcing cohesion less soil slopes by means of metal strips. Proceedings of the International Geotechnical Symposium on Theory and Practice of Earth Reinforcement, Kyushu, Japan, 289–294.
  10. Vucetic, M., Tufenkjian, M., Doroudian, M. (1993) Dynamic Centrifuge Testing of Soil-Nailed Excavations. Geotechnical Testing Journal, 16(2), 172–187.
  11. Mark, R.T. and Mladen, V. (2000) Dynamic failure mechanism of soil-nailed excavation models in centrifuge. Journal of Geotechnical and Geoenvironmental Engineering, 126(3), 227-235.
  12. Zhang, J.P., Zhang, J., Qui, T. (2001) Model test by centrifuge of soil nail reinforcements. Journal of Testing and Evaluation, 29(4), 315-328.
  13. Zhang, G., Cao, J., Wang, L. (2013) Centrifuge model tests of deformation and failure of nailing reinforced slope under vertical surface loading conditions. Soils and Foundations, 53(1), 117-129.
  14. Rotte, V.M., and Viswanadham, B.V.S. (2013) Centrifuge Model Studies on the Performance of Slopes with and without Nails Subjected to Seepage. Proceedings of Indian Geotechnical Conference, Roorkee, 1-8.
  15. Zhang, G., Cao, J., Wang, L. (2014) Failure behavior and mechanism of slopes reinforced using soil nail wall under various loading conditions. Soils and Foundations, 54(6), 1175-1187.
  16. Sivakumar Babu, G.L., and Murthy B.R.S. (2002) Analysis of construction factors influencing the behavior of soil nailed earth retaining walls. Ground Improvement, 6(3), 137–143.
  17. Cheuk, C.Y., Ng, C.W.W., and Sun, H.W. (2005) Numerical experiments of soil nails in loose fill slopes subjected to rainfall infiltration effects. Computers and Geotechnics, 32(4), 290–303.
  18. Sheikhbahaei, A.M., Halabian, A.M., and Hashemolhosseini, S.H. (2010) Analysis of soil nailed walls under harmonic dynamic excitations using finite difference method. Fifth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, San Diego, California.
  19. Wu, J.C., and Shi, R. (2012) Seismic Analysis of Soil Nailed Wall Using Finite Element Method. Advanced Materials Research, 535-537, 2027-2031.
  20. Jaya, V., and Annie, J. (2013) An Investigation on the Dynamic Behavior of Soil Nail Walls. Journal of Civil Engineering and Science, 2(4), 241-249.
  21. Itasca (1995) FLAC: Fast Lagrangian Analysis of Continua, Version 3.3, User Manual, Itasca Consulting Group, Inc., Minneapolis.
  22. Soheil, G., and Saidi, M. (2011) An Investigation on the Behavior of Retaining Structure of Excavation Wall Using Obtained Result from Numerical Modeling and Monitoring Approach (A Case Study of International "Narges Razavi 2 Hotel", Mashhad), Journal of Structural Engineering and Geotechnics.
  23. Komakpanah, A., and Yazdandoust, M., (2015) Investigation into the effect of earthquake index parameters on seismic performance of reinforced soil walls to select an appropriate design earthquake, 3.12(1.1), 17-26.
  24. Hashash, Y.M.A., Musgrove, M.I., Harmon, J.A., Groholski, D.R., Phillips, C.A., and Park, D. (2016) DEEPSOIL 6.1, User Manual.