Comparison of Numerical Methods for Piled Raft Foundations

Abstract:

The methodologies used to calculate piled raft foundations are normally more complex than conventional foundations due to the large number of variables involved in the problem. In the conventional block, the interaction variables considered are only between the pile and the soil. In the piled raft, all the interaction effects must be considered, as follows: plate-soil, plate-piles and piles-soil, simultaneously. The Finite Element Method (FEM) has proven to be a useful tool in analyzing these types of problems. This study aims at assessing the behavior of piled rafts using the Cesar-LCPC numerical tool, version 4.0, which is based on the finite element method. Literature cases of rafts supported by 9, 15 and 16 piles were analyzed. The results obtained were compared with analysis methods presented in the bibliography. The following parameters were assessed: relative spacing (S/D), relative length (L/D), relative stiffness between piles and the soil (K_PS), and settlement of piles and the raft. The spacing between piles has a significant influence on load distribution between piles and the raft. Very small spacing provides stiffness to the foundation, which then functions as a conventional pile foundation, in which only the piles absorb the load from the superstructure. The larger the L/D ratio, the lower the settlement and for a given modulus of elasticity of the pile, the increase in relative stiffness (K_PS) causes an increase in settlement. In all analyses, the data obtained corroborated the results presented by other methods published in the literature.

• Periodical: Advanced Materials Research (Volumes 838-841)
• Pages: 334-341
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.838-841.334
• Online since: November 2013
• Authors: Osvaldo de Freitas Neto, Renato P. Cunha, Olavo Francisco Santos*, Paulo J.R. Albuquerque, Jean R. Garcia
• Keywords: Foundation Settlement, Numerical Analysis, Piled Raft

References

[1] H. G. Poulos, Methods of Analysis of Piled Raft Foundations. A Report Prepared on Behalf of Technical Committee TC-18 on Piled Foundations. Chairman: Prof. Dr. Ir W.F. Van Impe. International Society of Soil Mechanics and Geotechnical Engineering, (2001).

DOI: 10.1061/40772(170)2

[2] L. De Sanctis, A. Mandolini , G. Russo and C. Viggiani. Some remarks on the optimum design of piled rafts., Proc., ASCE Deep Foundations 2002: An International Perspective on Theory, Design, Construction, and Performance, Reston, Va., (2002).

DOI: 10.1061/40601(256)30

[3] R. Katzenbach, U. Arslan, and J. Gutwald. A numerical study on pile foundation of the 300m high Commerzbank Tower in Frankfurt Main. Proc. 3 European Conf. on Numerical Methods in Geomechanics, Manchester, (1994) pp.271-277.

[4] T. Janda, R. P. Cunha, P. Kuklk and G. M. Anjos. Three Dimensional Finite Element Analysis and Back-analysis of CFA Standard Pile Groups and Piled Rafts Founded on Tropical Soil. Soils and Rocks, São Paulo, (2009), 32(1): 3-18.

DOI: 10.28927/sr.321003

[5] R.P. Cunha, J. M. Soares, and N. M. B. Mota. Optimizing a design of foundations, through the use of piled raft. Simp. Int. Estrutura-Solo em Edifícios, São Carlos, CD ROM (In Portuguese) , (2000).

[6] R. P. Cunha, H. G. Poulos and J. C. Small. Investigation of design alternatives for a piled raft case history. ASCE Journal of Geot. and Geoenv. Engineering, Agosto, Vol. 127, No. 8, pp.635-641, (2001).

DOI: 10.1061/(asce)1090-0241(2001)127:8(635)

[7] R. P. Cunha, J. E. Bezerra, J. C. Small and H. H. Zhang. Parametric analysis of piled rafts founded on a tropical clay of Brazil. IX Int. Conf. of Piling and Deep Foundation. Nice, Vol. Único, pp.249-256. (2002).

[8] R. P. Cunha and H. H. Zhang. (2006). Behavior of piled raft foundation systems under a combined set of loadings. 10th. Int. Conf. on Piling and Deep Foundations-DFI_2006. Amsterdam. pp.242-251. (2006).

[9] M. M. Sales, R. P. Cunha, Poulos, H.G. and J. C. Small. Simplified approach for load-settlement curve estimation of piled rafts. Soil and Rocks, v. 28: 1, pp.73-83. (2005).

[10] H. Kishida and G. G. Meyerhof. Bearing capacity of pile groups under eccentric loads in sand. Proc. 6th ICSMFE, Toronto, 2 : 270-274. (1965).

[11] A. W. Skempton. Discussion contribution: piles and pile foundations, settlement of pile foundations. Proc. 3rd ICSMFE, Zurich, 3: 172. (1953).

[12] G. G. Meyerhof. Compaction of sands and bearing capacity of piles. Journal of Geot. Eng. Div., ASCE, 85 (SM6): 1-29. (1959).

[13] A. S. Vesic. Experiments with instrumented pile groups in sand. Performance of deep foundations, ASTM Spec. Tech. Publ. n. 444, p.177–222. (1969).

[14] K. Terzaghi. Theoretical Soil Mechanics. Jonh Wiley and Sons, New York. (1943).

[15] H. G. Poulos and E. H. Davis. Pile foundations analysis and design. John Wiley and Sons. New York. (1980).

[16] M. F. Randolph and C. P. Wroth. Analysis of deformation of vertically loaded piles. Journal of Geot. Eng. Div., ASCE, 104(12): 1465-1488. (1978).

DOI: 10.1061/ajgeb6.0000729

[17] M. F. Randolph. Design methods for pile groups and piled rafts. State of art report. Proc. 13h Intern. Conf. on Soil Mechanics and Foundation Eng., New Delhi, v. 5, pp.61-82. (1994).

[18] M. M. Sales. Analysis of the behavior of piled rafts. Ph.D. Thesis, University of Brasília, Department of Civil and Environmental Engineering, Publication G. TD – 002A/00, 229 p. (2000). (In Portuguese).

[19] M. Ottaviani. Three-dimensional finite element analysis of vertically loaded pile groups. Géotechnique, v. 25, n. 2, pp.159-174. (1975).

DOI: 10.1680/geot.1975.25.2.159

[20] D. M. A. Bittencourt and B. E. A. Lima, Analysis of Factors piled raft interaction: Comparison of two numerical approaches. 136p. Completion of course work for graduation, Federal University of Goiás. (2009). (In Portuguese).

[21] R. S. Souza. Análise dos fatores de interação entre estacas em radier estaqueado: Comparação entre duas ferramentas numéricas. Dissertation submitted to the University Federal University of Goiás. (2010). (In Portuguese).

[22] H. G. Poulos, J. C. Small, J. C, L. D. Ta, J. Sinha and L. Chen. Comparison of some methods for analysis of piled rafts. XIV ICSMFE, Hamburg, Vol. 2, pp.1119-1129. (1997).

[23] M. F. Randolph. Design of Piled Raft Foundations. Cambridge University, Eng. Depart. Research Report, Soils TR143. (1983).

[24] H. G. Poulos. An approximate numerical analysis of pile-raft interaction. Int. Journal for Num & Anal. Meth. In Geomechanics. 18: 73-92. (1994).

DOI: 10.1002/nag.1610180202

[25] H. G. Poulos. Foundation Economy via Piled Raft Systems. Keynote Paper of Pile talk International' 91. Kuala Lumpur. pp.97-106. (1991).

[26] L. D. Ta and J. C. Small. Analysis of piled raft systems in layered soils. Int. Journal for Num. & Anal. Meth. in Geomechanics, Vol. 20, pp.57-72. (1996).

DOI: 10.1002/(sici)1096-9853(199601)20:1<57::aid-nag807>3.0.co;2-0

[27] J. Sinha. Piled Raft Foundations Subjected to Swelling and Shrinking Soils. PhD Thesis, Univ. of Sydney, Australia. (1997).

[28] F. Kuwabara. An elastic analysis for piled raft foundations in a homogeneous soil. Soils and Foundations, Vol. 29(1): 82-92. (1989).

DOI: 10.3208/sandf1972.29.82

[29] J. C. Small, and H. Zhang. Personal Communication. (1999).

[30] K. Yamashita. Analyses of piled raft model provided by ISSMGE TC-18-Part 2: Estimation by three dimensional finite element analysis. TC-18 Japonese Geot. Society Member´s Meeting of Piled Rafts, Tokyo, p.2. 1-2. 8. (1998).

[31] K. Horikoshi and M. F. Randolph. Analyses of piled raft model provided by ISSMGE TC-18 – Part 3: Estimation by simple approach and hybrid method HyPR. TC-18 Japonese Geot. Society Member´s Meeting of Piled Rafts, Tokyo, p.3. 1-3. 16. (1998).

[32] T. Matsumoto. Analyses of piled raft model provided by ISSMGE TC-18 – Part 4: Analyses of piled raft subjected to vertical loading and lateral loading. TC-18 Japanese. Geot. Society Member's Meeting on Piled Rafts. Tokyo. p . 4. 1-4. 7. (1998).

DOI: 10.3850/978-981-07-4623-0_kn-08