Effect of Footing Shape on Bearing Capacity and Settlement of Closely Spaced Footings on Sandy Soil

Authors: A. Shafaghat, H. Khabbaz, S. Moravej, Ah. Shafaghat

Abstract:

The bearing capacity of closely spaced shallow footings alters with their spacing and the shape of footing. In this study, the bearing capacity and settlement of two adjacent footings constructed on a sand layer are investigated. The effect of different footing shapes including square, circular, ring and strip on sandy soil is captured in the calculations. The investigations are carried out numerically using PLAXIS-3D software and analytically employing conventional settlement equations. For this purpose, foundations are modelled in the program with practical dimensions and various spacing ratios ranging from 1 to 5. The spacing ratio is defined as the centre-to-centre distance to the width of foundations (S/B). Overall, 24 models are analyzed; and the results are compared and discussed in detail. It can be concluded that the presence of adjacent foundation leads to the reduction in bearing capacity for round shape footings while it can increase the bearing capacity of rectangular footings in some specific distances.

Keywords: Bearing capacity, finite element analysis, loose sand, settlement equations, shallow foundation.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.2021705

References:

[1] Hashemi, S. H. and Mohammadi, M. (2011). A study on bearing capacity of circular foundations on sands, 6th National Congress on Civil Engineering, Semnan University, Semnan, Iran.
[2] Keshavarz, A. & Salehi, M. (2011). Bearing capacity of strip footings on two-layer clays, 6th National Congress on Civil Engineering, Semnan University, Semnan, Iran.
[3] Aliollahi, H. and Saber, A. (2014). A numerical investigation of the shape effect of ring foundations on their bearing capacity and settlement, The 8th National Congress of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran.
[4] Hosseini, S., & Salehi, M. (2016). Evaluation of strip footing behaviour resting on geogrid-reinforced soils, Sharif Journal of civil engineering, 31(2), 83-88.
[5] Anvari, O., Lotfollahi Yaghin, M. A. (2016). A study on the Scale Effect of footing settlement in clay using Plaxis, the 2nd international conference on civil and environmental engineering conference, Istanbul, Turkey.
[6] Kumar, J., & Ghosh, P. (2005). Bearing capacity factor N γ for ring footings using the method of characteristics. Canadian geotechnical journal, 42(5), 1474-1484.
[7] Karaulov, A. M. (2006). Experimental and theoretical research on the bearing capacity of ring-foundation beds. Soil Mechanics and Foundation Engineering, 43(2), 37-40.
[8] Loukidis, D., & Salgado, R. (2009). Bearing capacity of strip and circular footings in sand using finite elements. Computers and Geotechnics, 36(5), 871-879.
[9] Azzam, W. R., & Nasr, A. M. (2015). Bearing capacity of shell strip footing on reinforced sand. Journal of advanced research, 6(5), 727-737.
[10] Cicek, E., Guler, E., & Yetimoglu, T. (2015). Effect of reinforcement length for different geosynthetic reinforcements on strip footing on sand soil. Soils and Foundations, 55(4), 661-677.
[11] Hataf, N., & Shafaghat, A. (2015). Numerical comparison of bearing capacity of tapered pile groups using 3D FEM. Geomech Eng, 9(5), 547-567.
[12] Hataf, N., & Shafaghat, A. (2015). Optimizing the bearing capacity of tapered piles in realistic scale using 3D finite element method. Geotechnical and Geological Engineering, 33(6), 1465-1473.
[13] Taiebat, H. A., & Carter, J. P. (2000). Numerical studies of the bearing capacity of shallow foundations on cohesive soil subjected to combined loading. Géotechnique, 50(4), 409-418.
[14] Brinkgreve, R. B. J., & Vermeer, P. A. (1998). Plaxis manual. Version, 7, 5-1.
[15] Vesic, A. S. (1973). Analysis of ultimate loads of shallow foundations. Journal of Soil Mechanics & Foundations Div, 99(sm1).