研究生: |
DO TUAN NGHIA DO - TUAN NGHIA |
---|---|
論文名稱: |
FACTOR OF SAFETY AGAINST BASAL HEAVE FOR DEEP EXCAVATIONS IN SOFT CLAY USING THE FINITE ELEMENT METHOD FACTOR OF SAFETY AGAINST BASAL HEAVE FOR DEEP EXCAVATIONS IN SOFT CLAY USING THE FINITE ELEMENT METHOD |
指導教授: |
歐章煜
Chang-Yu Ou |
口試委員: |
謝百鈎
none 楊國鑫 none 卿建業 none |
學位類別: |
碩士 Master |
系所名稱: |
工程學院 - 營建工程系 Department of Civil and Construction Engineering |
論文出版年: | 2011 |
畢業學年度: | 99 |
語文別: | 英文 |
論文頁數: | 196 |
中文關鍵詞: | basal heave 、factor of safety 、excavation 、finite element method |
外文關鍵詞: | basal heave, factor of safety, excavation, finite element method |
相關次數: | 點閱:195 下載:13 |
分享至: |
查詢本校圖書館目錄 查詢臺灣博碩士論文知識加值系統 勘誤回報 |
The objective of this thesis is to study the basal heave of excavations using the numerical method. This study firstly confirmed advantage of finite element analysis with updated mesh over the analysis without updated mesh for large deformation problem. Then analysis with updated mesh and strength reduction method was adopted to analyze three failure basal heave or near failure excavations in soft soil. The automatic c – phi reduction method, the manual c – phi reduction method, the angle method and the intersection method were used to justify if excavations reached failure or near failure conditions. The automatic c – phi reduction method defines factor of safety as strength reduction ratio at which displacement increases largely. Based on convergence criteria, the manual c – phi reduction method determines the highest value of strength reduction ratio as safety factor at which equilibrium state remains. On the other hand, the angle method considers kick out phenomenon of the retaining wall as failure state. For the intersection method, the relationship between the displacement and strength reduction ratio was plotted and factor of safety was strength reduction ratio corresponding to intersection point of curve. Moreover, a series of parametric studies was performed to study the effect of excavation width on the evaluation of factor of safety. In general, the factors of safety predicted by the numerical methods consisted with the plastic point distributions when excavation changed from narrow to wide shape.
The objective of this thesis is to study the basal heave of excavations using the numerical method. This study firstly confirmed advantage of finite element analysis with updated mesh over the analysis without updated mesh for large deformation problem. Then analysis with updated mesh and strength reduction method was adopted to analyze three failure basal heave or near failure excavations in soft soil. The automatic c – phi reduction method, the manual c – phi reduction method, the angle method and the intersection method were used to justify if excavations reached failure or near failure conditions. The automatic c – phi reduction method defines factor of safety as strength reduction ratio at which displacement increases largely. Based on convergence criteria, the manual c – phi reduction method determines the highest value of strength reduction ratio as safety factor at which equilibrium state remains. On the other hand, the angle method considers kick out phenomenon of the retaining wall as failure state. For the intersection method, the relationship between the displacement and strength reduction ratio was plotted and factor of safety was strength reduction ratio corresponding to intersection point of curve. Moreover, a series of parametric studies was performed to study the effect of excavation width on the evaluation of factor of safety. In general, the factors of safety predicted by the numerical methods consisted with the plastic point distributions when excavation changed from narrow to wide shape.
REFERENCES
Aas, G. (1984). “Stability problems in a deep excavation in clay.” Proc., 1st Int. Conf. on
Case Histories in Geotech. Engrg, pp.315-323
Aas, G. (1976). “Application of slurry trench walls for tunnel project in Oslo clay.” Proc., 6th
Europ. Conf. on Soil Mechanics and Geotechnical Engineering, pp. 617 – 620.
Bjerrum, L., and Eide, O. (1956). ‘‘Stability of strutted excavations in clay.’’ Geotechnique, 6,
pp. 115–128.
Brinkgreve, R. B. J. & Baker, H. L. (1991). “Non – linear finite element analysis of safety
factors.” Proceeding 7th Int. Conf. on Comp. Methods and Advances in Geomechanics, Cairns,
Australia, pp. 1117 – 1122.
Donald, I.B. and Giam, S.K. (1988), “Application of the nodal displacement method to slope
stability analysis.” Proceeding5th Australia – New Zealand Conf. on Geomechanics, pp 456 -
460.
Goh, A.T.C (1994). “Estimating basal – heave stability for braced excavations in soft clay.”
Journal of the Soil Mechanics and Foundation Division, ASCE, Vol. 120, No. 8, pp. 1430 –
1436.
Handy Faheem, Fei Cai, Keizo Ugai, Toshiyuki Hagiwara (2003). “Two – dimensional base
stability of excavations in soft soils using FEM.” Comput. Geotech. Vol 30, No. 2, pp 141 –
163.
Lin, H. D. and Lin, C. B. (1999). “A preliminary study for the frictional resistance and loading
factor of the cast – in – site pile.” Journal of the Chinese Institute of Civil and Hydraulic
Engineering, Vol. 11, No. 1, pp. 13 – 21.
Liu, C. C., Hsieh, H. S., and Huang, C. S. (1997), “A study of the stability analysis for deep
excavations in clay.” The Seventh Geotechnical Conference, Taipei, pp. 629 – 638.
NAVFAC DM 7.2 (1982), “Foundations and Earth Structures, Design Manual 7.2.” Department
of the Navy, USA.
Norwegian Geotechnical Institute (NGI). (1962 ). ‘‘Measurements at a strutted excavation, Oslo
Subway, Vaterland 1, km 1373.’’ Tech. Rep. No. 6, Oslo.
Ou, C.Y. (2006). “Deep excavation: theory and practice.” Taylor & Francis.
Plaxis. (2010). “Material models manual.”
Potts, D. M., Zdravkovic, L. (1999). “Finite element analysis in geotechnical engineering:
theory.” Thomas Telford.
Reddy, A.S. and Srinivasan, R.J. (1967), “Bearing capacity of footing on layered clay.” Journal
of the Soil Mechanics and Foundation Division, ASCE, Vol. 93, No. 2, pp. 83 – 99.
Van Langen, H. (1991). “Numerical analysis of soil structure interaction.” Ph.D. Thesis, Delft
University of Technology, the Netherlands.
Zienkiewicz, O. C., Humpheson, C. & Lewis, R. W. (1975). “Associated and non – associated
visco – plasticity and plasticity in soil mechanics.” Geotechnique, Vol. 25, No. 4, pp. 671 –
689.