مطالعه ی استاتیکی و شبه استاتیکی اثر وجود لایه ی سست رسی بر رفتار سپری های فلزی

نوع مقاله : Articles

نویسندگان

1 دانشگاه صنعتی قم

2 گروه مهندسی عمران، دانشگاه صنعتی قم

چکیده

سپری­های فلزی به‌طور گسترده در پروژه­های مهندسی عمران به‌عنوان سازه نگهبان مورد استفاده قرار می­گیرد. مشخصات پروفیل خاک در عمق متفاوت بوده و در برخی مواقع ممکن است لایه­ی سست در عمق­ها و موقعیت­های مختلف وجود داشته باشد. این مسئله می­تواند اثرات متفاوتی را در طی عملیات گودبرداری بر تغییر شکل سطح زمین، نیروها و لنگرهای وارد بر سپرهای فولادی و مهارها نسبت به حالتی که خاک نسبتاً یکنواخت است داشته باشد که در طراحی سپری­ها و مهارها بایستی در نظر گرفته شود. در این تحقیق یک گود عمیق تعریف و مدل‌سازی شده و با استفاده از روش اجزای محدود مورد تحلیل قرار گرفته است. عمق گود به سه لایه­ی رسی تقسیم شده است. یکی از این سه لایه، لایه­ی سست رسی می­باشد که موقعیت آن در لایه­ی بالا، وسط و پایین در مدل­هایی به‌طور جداگانه تغییر می­کند. نتایج حاصل از تحلیل با نتایج مدلی که فاقد لایه­ی سست می­باشد مقایسه می­شود. ازآنجاکه سازه نگهبان ممکن است دائمی‌ باشد، پایداری بلندمدت آن نیز بایستی مد نظر قرار گیرد. ازاین‌رو در نظر گرفتن نیروهای لرزه­ای ضروری است. بدین منظور در این تحقیق از تحلیل شبه استاتیکی با شتاب g 3/0 استفاده شده است. نتایج نشان می­دهد که وجود لایه­ی سست فوقانی بر تغییر شکل­های سطح زمین و سپری اثرات کاهنده دارد. همچنین وجود لایه­ی سست رسی زیر لایه­های سخت خاک رس سبب افزایش لنگر خمشی و نیروهای وارد بر سپری می­شود.

کلیدواژه‌ها


عنوان مقاله [English]

Static and Pseudo Static Study of Loose Clay Layer Effects on Steel Sheet Pile Walls Behaviors

نویسندگان [English]

  • Behrouz Ahmadpour 1
  • Masoud Amel Sakhi 2
1 Qom University of Technology, Qom, Iran
2 Department of Civil Engineering, Qom University of Technology, Qom, Iran
چکیده [English]

Introduction
Usually, the construction of new multi-story buildings require deep supported excavation. Steel sheet pile walls
are being widely used in civil engineering projects for excavation support systems. Many researches have performed
about various problems of steel sheet piles, like steel sheet pile behaviors; using of sheet pile as a permanent
structure; long term performance of sheet piles; Vertical bearing capacity; construction of steel sheet pile walls on
sloping ground; performance of steel sheet pile wall for supporting an excavation in urban environment. Soil is not
uniform in depth, sometimes loose soil layer may exist in various depth and situations. This issue can cause different
effects on ground surface displacements, forces and moments acting on sheet pile and struts during excavation
procedure, compared with status that soil is uniform in depth, especially in seismic conditions that must be
considered in design of sheet piles and struts.
Methodology
In this study a deep excavation by using finite element method is analyzed. Excavation’s depth is divided to
three clayey layers. One of three layers is loose clay layer that its positions is modelled in three different situations,
top, middle and bottom. Obtained results are compared with excavation without loose layer. Since excavation
support system may be a permanent structure, long term stability must be considered. Pseudo static analysis is
performed by applying 0.3g horizontal acceleration.
Models are analyzed in different situations, dry and saturation. Width and depth of considered excavation are 10
and 12 meters, respectively. The first strut is installed beneath one meter of ground surface and subsequent struts are
modeled in 3 meters spacing from each other so that finally, four struts are considered along the depth of excavation.
Change percent of different parameters in models with clay loose layer is calculated in comparison with model
without clay loose layer.
Results
According to comparative obtained results it can be concluded that:
1. Existence of a loose clay layer on two stiff clay layers that thicknesses of all three layers are same, generally
has reducing effects on soil and sheet piles deformations, forces and bending moments of sheet piles.
2. With increasing depth of loose clay layer, lateral deformation, shear force and bending moment acting on
sheet piles are increased. In depth equal to two times of loose layer thickness, these parameters have
maximum values. In fact, with increasing sheet piles horizontal displacement, bending moments are increased.
3. Maximum horizontal displacement of the soil is in condition that loose clay layer is bottom layer.
4. When loose clay layer is located on the middle or bottom layer, shear forces acting on sheet piles are greater
due to loose layer located on upper layer.
5. Generally, it can be said, with increasing depth and location of loose clay layer, affecting parameters on sheet
piles and struts behaviors are increased.
6. Existence of loose clay layer changes axial force of struts. This issue must be considered in design of sheet
piles, especially in design of middle struts.
7. Saturated situations increase axial force of struts.

کلیدواژه‌ها [English]

  • Sheet Piling
  • deformation
  • Strut
  • Pseudo Static Analysis
  1. Ou, C.Y. (2006) Deep Excavation, Theory and Practice. Taylor & Francis, London.
  2. Shao, Y. and Macari, E.J. (2008) Information feedback analysis in deep excavations. Inter-national Journal of Geomechanics, 8(1), 91-103.
  3. Underwood, C. and Greenlee, R. (2010) Steel sheet pile used as permanent foundation and retention systems-design and construction. Earth Retention Conference, 3, 129-136.
  4. Ramsden, M. and Griffiths, T. (2010) Steel sheet pile wall wale rehabilitation. Ports 2010, 193-202.
  5. Sellmeijer, J., Cools, J., Decker, J., and Post, W. (1995) Hydraulic resistance of steel sheet pile joints. Journal of Geotechnical Engineering, 121(2), 105-110.
  6. Ohori, K., Takahashi, K., Kawai, Y., and Shiota, K. (1988) Static analysis model for double sheet‐pile wall structures. Journal of Geotechnical Engineering, 114(7), 810-825.
  7. Terzaghi, K. and Peck, R.B. (1996) Soil Mechanics in Engineering Practice. 3rd ed., John Wiley & Sons, Inc., New York, NY.
  8. USACE (1991) Design of Pile Foundations. US Army Corps of Engineers Engineering Manual EM 1110-2-2906.
  9. Lee, S.H., Kim, B.I., and Han, J.T. (2012) Prediction of penetration rate of sheet pile installed in sand by vibratory pile driver. KSCE Journal of Civil Engineering, 16(3), 316-324.
  10. Gopal Madabhushi, S., and Chandrasekaran, V. (2005) Rotation of Cantilever Sheet Pile Walls. Journal of Geotechnical and Geoenvironmental Engineering, 131(2), 202-212.
  11. Bilgin, Ö. and Erten, M. (2009) Anchored sheet pile walls constructed on sloping ground. Contemporary Topics in Ground Modification Problem Soils and Geo-Support, 145-152.
  12. Gurinsky, M. (2001) Long-term strength of sheet pile bulkheads with ground anchors. Ports '01, 1-8.
  13. Hu, Y., Liu, G., and Zhao, Y. (2013) Calculation method of deformation and inner force of a sheet pile wall with relieving platform. ICTE 2013, 168-174.
  14. Zdravkovic, L., Potts, D.M., and St John, H.D. (2005) Modelling of a 3D excavation in finite element analysis. Geotechnique, 55(7), 497-513.
  15. Laefer, D.F., Ceribasi, S., Long, J.H. and Cording, E.J. (2009) Predicting RC frame response to excavation-induced settlement. Journal of Geotechnical and Geoenvironmental Engineering, 135(11), 1605-1619.
  16. Son, M. and Cording, E.J. (2005) Estimation of building damage due to excavation induced ground movements. Journal of Geotechnical and Geoenvironmental Engineering, 131(2), 162-177.
  17. Long, M. (2001) Database for retaining wall and ground movements due to deep excavations. Journal of Geotechnical and Geoenvironmental Engineering, 127(3), 203-224.
  18. Leonidou, E.A., Athanasopoulos, G.A., and Pelekis, P.C. (2001) Deep supported excavation for the underground parking of the Hellenic Parliament: measured vs. predicted behavior. Proceedings of the 15th International Conference on Soil Mechanics and Geotechnical Engineering, Instanblul, Turkey, 2, 1493-1496.
  19. Moorman, C. (2004) Analysis of wall and ground movements due to deep excavations in soft soil based on a new worldwide database. Journal of Soils and Foundations, 44(1), 87-98.
  20. Zekkos, D.P., Athanasopoulos, A.G., and Athanasopoulos, G.A. (2004) Deep supported excavation in difficult ground conditions for the construction of a two-story underground parking garage in the city of Patras, Greece. Proceedings of 5th Internatiolnal Conference on Case Histories in Geotech. Engineering, New York, N.Y.
  21. Wong, I.H., Poh, T.Y., and Chuah, H.L. (1997) Performance of excavations for depressed express-way in Singapore. Journal of Geotechnical and Geoenvironmental Engineering, 123(7), 617-625.
  22. Yoo, C.S. (2001) Behavior of braced and anchored walls in soils overlying rock. Journal of Geotechnical and Geoenvironmental Engineering, 127(3), 225-233.
  23. Ma, J., Berggren, B., Stille, H., and Hintze, S. (2010) Deformation of anchor-sheet pile wall retaining system at deep excavations in soft soils overlying bedrock. Deep and Underground Excavations, 126-131.
  24. Finno, R.J. and Callvello, M. (2005) Supported excavations: the observational method and inverse modeling. Journal of Geotechnical and Geoenvironmental Engineering, 131(7), 826-836.
  25. Day, R.A., and Potts, D.M. (1993) Modelling sheet pile retaining walls. Journal of Computers and Geotechnics, 15(3), 125-143.
  26. Bilgin, Ö. (2012) Lateral earth pressure coeffi-cients for anchored sheet pile walls. International Journal of Geomechanics, 12(5), 584-595.
  27. Sahajda, K. (2014) Ground anchor loads measured on an excavation sheet pile wall. Tunneling and Underground Construction, 974-983.
  28. Athanasopoulos, G., Vlachakis, V., and Pelekis, P. (2011) Installation and performance of a steel sheet pile wall for supporting an excavation in urban environment. Geo-Frontiers 2011, 3370-3380.
  29. Das, B.M. and Sobhan, Kh. (2013) Principles of Geotechnical Engineering. Eighth Edition, CENGAGE Learning, Stamford, USA.