NUMERICAL ANALYSIS OF RING FOOTINGS RESTING ON SAND BEDS

Hussein, Mohamed M. A.

doi:10.21608/sej.2021.155946

NUMERICAL ANALYSIS OF RING FOOTINGS RESTING ON SAND BEDS

Document Type : Original research articles

Author

Mohamed M. A. Hussein

Civil Eng. Departement, Faculty of Eng., Sohag University, Sohag, Egypt.

10.21608/sej.2021.155946

Abstract

Nowadays, more and more ring footings are used in practice specially for axi-symmetric structures. In this paper, a numerical analysis was performed using PLAXIS software for calculating bearing capacity factor for rough circular and ring footings on sand. The analysis was carried out using Mohr-Coulomb’s criterion for soil. The bearing capacity was calculated for rough circular and ring footings and then the bearing capacity factor was calculated. The effect of different factors such as angle of internal friction of sand, , radius ratio () and different external diameters of circular and ring footings () were studied. The load settlement curves for circular and ring footings were compared, with emphasis on the ultimate bearing capacity. The analysis indicated that radius ratio has a significant effect on the ultimate bearing capacity of ring footings, were ultimate bearing capacity decreases with increasing radius ratio. However, little or no change in bearing capacity factor was observed. Also, the results indicated that there is no significant effect of footing size () on the bearing capacity factor value. It is found that the space in ring footing () has a significant effect on the change of failure mode of soil from both local and punching shear failure to a general shear failure for loose and medium sand, respectively. Also, the space in ring footing has a significant effect on the length and width of failure zone under ring footings.
Nowadays, more and more ring footings are used in practice specially for axi-symmetric structures. In this paper, a numerical analysis was performed using PLAXIS software for calculating bearing capacity factor

for rough circular and ring footings on sand. The analysis was carried out using Mohr-Coulomb’s criterion for soil. The bearing capacity was calculated for rough circular and ring footings and then the bearing capacity factor

was calculated. The effect of different factors such as angle of internal friction of sand,

, radius ratio (

) and different external diameters of circular and ring footings (

) were studied. The load settlement curves for circular and ring footings were compared, with emphasis on the ultimate bearing capacity. The analysis indicated that radius ratio has a significant effect on the ultimate bearing capacity of ring footings, were ultimate bearing capacity decreases with increasing radius ratio. However, little or no change in bearing capacity factor

was observed. Also, the results indicated that there is no significant effect of footing size (

) on the bearing capacity factor

value. It is found that the space in ring footing (

) has a significant effect on the change of failure mode of soil from both local and punching shear failure to a general shear failure for loose and medium sand, respectively. Also, the space in ring footing has a significant effect on the length and width of failure zone under ring footings.

Keywords

References

[1] G. G. Meyerhof, “The ultimate bearing capacity of foudations,” Geotechnique, vol. 2, no. 4, pp. 301-332, 1951.

[2] K.Terzaghi, “Theoretical soil mechanics,” johnwiley & sons. New York, pp.11-15. 1943.

[3] D. V. Griffiths, “Computation of collapse loads in geomechanics by finite elements,” Ingenieur-Archiv, vol. 59, no. 3 pp. 237-244, 1989.

[4] N. Manoharan, and S. P. Dasgupta, “Bearing capacity of surface footings by finite elements,” Computers & structures, vol. 54, no. 4, pp. 563-586, 1995.

[5] Hans L. Erickson and Andrew Drescher, “Bearing capacity of circular footings,” Journal of geotechnical and geoenvironmental engineering, vol. 128, no. 1, pp. 38-43, 2002.‏

[6] Sam Frydman and Harvey J. Burd, “Numerical studies of bearing-capacity factor ,” Journal of geotechnical and geoenvironmental engineering, vol. 123, no. 1, pp. 20-29, 1997. ‏

[7] K. E. Egorov, “Calculation of bed for foundation with ring footing,” In Proc. 6 th International Conference of Soil Mechanics and Foundation Engineering, vol. 2, pp. 41-45. 1965.

[8] D. M. Milovic, “Stresses and displacements produced by a ring foundation,” In Proceedings of the eighth international conference on soil mechanics and foundation engineering, Moscow, vol. 3, pp. 167-71. AA Balkema Rotterdam, The Netherlands, 1973.

[9] J. E. Bowles, "Foundation analysis and design," 5th Edition. McGraw-Hill, New York, 1997.

[10] J. H. Boushehrian, and N. Hataf, “Experimental and numerical investigation of the bearing capacity of model circular and ring footings on reinforced sand,” Geotextiles and Geomembranes, vol. 21, No. 4, pp. 241-256, 2003.

[11] N. Hataf, M. Razavi, “Model tests and finite element analysis of bearing capacity of ring footings on loose sand,” Iranian Journal Of Science And Technology Transaction B- Engineering, vol. 27, no. B1, 0-0, 2003.

[12] S. Saran, N. M. Bhandari, and M. M. A. Al-Smadi, “Analysis of eccentrically–obliquely loaded ring footings on sand,” Indian Geotechnical Journal, vol. 33, no. 4, pp. 422-446, 2003. ‏

[13] J. Kumar and P. Ghosh, “Bearing capacity factor for ring footings using the method of characteristics,” Canadian geotechnical journal, vol. 42, no. 5, pp. 1474-1484, 2005. ‏

[14] L. Zhao, and J. H. Wang, “Vertical bearing capacity for ring footings,” Computers and Geotechnics, vol. 35, no. 2, pp. 292-304, 2008.

[15] R. B. J. Brinkgreve, “PLAXIS 2D user manual”, version 8, Balkema, Rotterdam, Netherlands, ed. 2002.

[16] M. M. Ahmed, “Stability of footings on reinforced and unreinforced sandy slopes,” Ph.D.Thesis, Civil Eng. Dep., Assiut University, 2006.

[17] S. W. Sloan, and M. F. Randolph, “Numerical prediction of collapse loads using finite element methods,” International Journal for Numerical and Analytical Methods in Geomechanics, vol. 6, no. 1, pp. 47-76, 1982.