Failure mechanism and soil deformation pattern of soil beneath interfering square footings

Document Type : Research


1 PhD , Civil Engineering Department , K.N. Toosi University of Technology, Tehran Iran

2 Professor, Civil Engineering Department, K.N. Toosi University of Technology, Tehran, Iran.


In this research, the variation of ultimate bearing capacity, failure mechanism and deformation pattern of soil beneath two closely square footings have been studied using numerical methods. It is assumed that the adjacent footings are constructed on the surface of sand. The presented numerical analyses are based on explicit-finite-difference code, FLAC3D. The elasto-plastic behavior of soil is modeled by using Mohr-Coulomb failure criteria along with associated flow rule for the soil. The reliability of constructed numerical simulation is investigated using available data on interfering footings. In addition, a large scale test is performed on two closely spaced square footings. Failure mechanism and deformation pattern are compared with the results obtained from numerical data. A pretty well agreement is observed between numerical and experimental results. The numerical analyses have shown a significant influence of interference on the failure mechanism and deformation pattern of the soil as well as the footing ultimate bearing capacity.


1. Bolton, M. D., and Lau, C. K., 1993. Vertical bearing capacity factors for circular and strip footings on Mohr-Coulomb soil. Canadian Geotechnical Journal, 30, pp. 1024-1033. [DOI:10.1139/t93-099]
2. Das, B.M., and Larbi-Cherif, S. 1983. Bearing Capacity of Two Closely Spaced Shallow Foundations on Sand. Soils and Foundations, 23(1), pp. 1-7. [DOI:10.3208/sandf1972.23.1]
3. De Borst, R., and Vermeer, P.A. 1984. Possibilities and Limitations of Finite Elements for Limit Analysis. Geotechnique, 34(2), pp. 199-210. [DOI:10.1680/geot.1984.34.2.199]
4. Erickson, H.L, and Drescher, A. 2002. Bearing Capacity of Circular Footings. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 128(1), pp. 38-43. [DOI:10.1061/(ASCE)1090-0241(2002)128:1(38)]
5. FLAC-Fast Lagrangian Analysis of Continua, Version 2.1., 2001. ITASCA Consulting Group, Inc., Minneapolis.
6. Frydman, S., and Burd, H.J. 1997. Numerical Studies of Bearing Capacity Factor N. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 123(1), pp. 20-29. [DOI:10.1061/(ASCE)1090-0241(1997)123:1(20)]
7. Ghazavi, M., and Lavasan, A.A., 2007. Influence of Interference on Bearing Capacity of Strip Footing on Reinforced Sand. In Proceedings of 5th International Symposium on Earth Reinforcement, pp. 431-436, Fukuoka, Japan.
8. Ghazavi, M., and Lavasan, A.A., 2008. Interference effect of shallow foundations constructed on sand reinforced with geosynthetics. Geotextiles and Geomembranes, vol. 26, pp. 404-415. [DOI:10.1016/j.geotexmem.2008.02.003]
9. Golder H.Q., 1941. The ultimate bearing pressure of rectangular footings. Journal of the Institution of Civil Engineers, 17(2), pp. 161-174. [DOI:10.1680/ijoti.1941.13728]
10. Griffiths, D.V., 1982. Computation of bearing capacity factors using finite elements. Geotechnique, 32(3), pp. 195-202. [DOI:10.1680/geot.1982.32.3.195]
11. Hansen, B.J., 1970. A Revised and Extended Formula for Bearing Capacity. Danish Geotechnical Institute Copenhagen, Denmark. Bul., No. 28, pp. 21.
12. Hjiaj, M., Lyamin, A.V., Sloan, S.W., 2004. Numerical Limit Analysis Solutions for the Bearing Capacity Factor N. International Journal of Solids and Structures, vol. 42, pp. 1681-1704. [DOI:10.1016/j.ijsolstr.2004.08.002]
13. Kumar, J., and Ghosh, P. 2007. Ultimate Bearing Capacity of Two Interfering Rough Strip Footings. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 7(1), pp. 53-62. [DOI:10.1061/(ASCE)1532-3641(2007)7:1(53)]
14. Kumar, J., Kouzer, K.M., 2007. Bearing capacity of two interfering footings, International Journal for Numerical and Analytical Methods in Geomechanics. DOI: 10.1002/nag.625 [DOI:10.1002/nag.625]
15. Kumar, A., and Saran, S. 2003. Closely Spaced Footings on Geogrid-Reinforced Sand. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 129(7), pp. 660-664. [DOI:10.1061/(ASCE)1090-0241(2003)129:7(660)]
16. Lee, J., and Salgado, R. 2005. Estimation of Bearing Capacity of Circular Footings on Sands Based on Cone Penetration Test. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 131(4), pp. 442-452. [DOI:10.1061/(ASCE)1090-0241(2005)131:4(442)]
17. Lee, J., Salgado, R., and Kim, S. 2005. Bearing Capacity of Circular Footings under Surcharge Using State-Dependent Finite Element Analysis. Computers and Geotechnics, vol. 32, pp. 445-457. [DOI:10.1016/j.compgeo.2005.07.005]
18. Meyerhof, G.G., 1952. The Ultimate Bearing Capacity of Foundations. Geotechnique, 3(2), pp. 301-332. [DOI:10.1680/geot.1951.2.4.301]
19. Michalowski R.L., 2001. Upper-bound load estimates on square and rectangular footings, Géotechnique, 51(9), pp. 787-798. [DOI:10.1680/geot.51.9.787.41038]
20. Michalowski, R.L., and Dawson, E.M., 2002. Three-Dimensional Analysis of Limit Loads on Mohr-Coulomb Soil. Foundations of Civil and Environmental Engineering. No. 1, pp. 137-147.
21. Saran, S., Kumar, S., Grag, K.G., and Kumar, A., 2006. Analysis of square and rectangular footings subjected to eccentric-inclined load resting on reinforced sand. Geotechnical and Geological Engineering, DOI: 10.1007/s10706-006-0010-7. [DOI:10.1007/s10706-006-0010-7]
22. Stuart, J.G. 1962. Interference between Foundations with Special Reference to Surface Footings in Sand. Geotechnique, 12(1), pp. 15-23. [DOI:10.1680/geot.1962.12.1.15]
23. Terzaghi, K., 1943. Theoretical Soil Mechanics. Wiley, Inc, New York. [DOI:10.1002/9780470172766]
24. Vesic, A.S. 1973. Analysis of Ultimate Loads of Shallow Foundations. Journal of Soil Mechanics and Foundations, ASCE, 99(1), pp. 45-73.
25. Ukritchon, B., Whittle, A.J., Klangvijit, M., 2003. Calculations of Bearing Capacity Factor N Using Numerical Limit Analyses. Journal of Geotechnical and Geoenvironmental Engineering, ASCE 129 (6), pp. 468-474. [DOI:10.1061/(ASCE)1090-0241(2003)129:6(468)]
26. Woodward, P.K., and Griffiths, D.V., 1998. Observations on the computation of the bearing capacity factor Ng by finite elements. Geotechnique, 48(1), pp. 137-141. [DOI:10.1680/geot.1998.48.1.137]
27. Yin, J.H., Wang, Y.J., and Selvadurai, A.P.S., 2001. Influence of Nonassociativity on the Bearing Capacity of a Strip Footing. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 127(11), pp. 985-989. [DOI:10.1061/(ASCE)1090-0241(2001)127:11(985)]