Mitigating the uneven settlement of nearby strip footings on loose saturated sand using concrete pedestals: A model test study

Document Type : Article


1 Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan, Iran

2 Geotechnical Engineering Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, Iran.

3 Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Isfahan, Iran.


Abstract: Adjacency and interfering of footings are a matter of importance in geotechnical engineering. The researchers have focused on the adjacency of the footings by several approaches, but the mechanism of nearby footings under unequal and non-simultaneous surcharges have not been explored to date. In this study, two series tests were conducted using small scale 1g models to investigate the behavior of the two adjacent footings under reinforced and unreinforced soil conditions. The footings were installed with different spacing and rested on loose saturate sand. The ultimate bearing capacity, settlement, and tilting of footings were evaluated when the footings are rested on unreinforced sand as well as the sand bed reinforced by concrete pedestals. The results indicate that reinforcing the new footing by three concrete pedestals in the spacing to footing's width ratio (S/B) of 0 (i.e., two coherent footings) results in 67% increase of the bearing capacity of the new footing compared to that of the unreinforced condition. Also, the settlement and tilting of the old footing adjacent to the new footing decrease respectively up to 250% and 600% in comparison to those of the unreinforced condition.


Main Subjects

1. Stuart, J.G. "Interference between foundations, with special reference to surface footings in sand", Geotechnique, 12(1), pp. 15-22 (1962).
2. Ghazavi, M. and Alimardani Lavasan, A. "Interference effect of shallow foundations constructed on sand reinforced with geosynthetics", Geotextiles and Geomembranes, 26, pp. 404-415 (2008).
3. Kouzer, K.M. and Kumar, J. "Ultimate bearing capacity of a footing considering the interference of an existing footing on sand", Geotechnical and Geological Engineering, 28, pp. 457-470 (2010).
4. Ghazavi, M. and Alimardani Lavasan, A. "Behavior of closely spaced square and circular footings on reinforced sand", Soils and Foundations, 52(1), pp. 160-167 (2012).
5. Srinivasan, V. and Ghosh, P. "Experimental investigation on interaction problem of two nearby circular footings on layered cohesionless soil", Geomechanics and Geoengineering, 8(2), pp. 97-106 (2013).
6. Noorzad, R. and Manavirad, E. "Bearing capacity of two close strip footing on soft clay with geotextile", Arabian Journal of Geoscience, 7(2), pp. 623-639 (2014).
7. Ghosh, P., Basudhar, P.K., Srinivasan, V., and Kunal, K. "Experimental studies on interference of two angular footings resting on surface of two layer cohesionless soil deposit", International Journal of Geotechnical Engineering, 9(4), pp. 422-433 (2015).
8. Nainegali, L., Basudhar, P.K., and Ghosh, P. "Interference of two asymmetric closely spaced strip footings resting on nonhomogeneous and linearly elastic soil bed", International Journal of Geomechanics, 13(6), pp. 840-851 (2013).
9. Salamatpoor, S., Jafarian, Y., and Hajiannia, A. "Bearing capacity and uneven settlement of consecutively-constructed adjacent footings rested on saturated sand using model tests", International Journal of Civil Engineering, 17, pp. 737-749 (2019).DOI: 10.1007/s40999-018-0295-y.
10. ASTM D422, Standard Test Method for Particle-Size Analysis of Soils, ASTM International, West Conshohocken, PA (2003).
11. Jafarian, Y., Ghorbani, A., Salamatpoor S., and Salamatpoor, S. "Monotonic triaxial experiments to evaluate steady-state and liquefaction susceptibility of Babolsar sand", Journal of Zhejiang University Science-A, 14(10), pp. 739-750 (2013).
12. Jafarian, Y., Mehrzad, B., Lee, C.J., and Haddad, A.H. "Centrifuge modeling of seismic foundationsoil- foundation interaction on liquefiable sand", Soil Dynamics and Earthquake Engineering, 97, pp. 184-204 (2017).
13. Salamatpoor, S. and Salamatpoor, S. "Evaluation of Babolsar sand behaviour by using static triaxial tests and comparison with case history", Open Journal of Civil Engineering, 4(3), pp. 181-197 (2014).
14. ASTM C150/C150M-17 "Standard specification for Portland cement", ASTM International, West Conshohocken, PA (2017).
15. Salamatpoor, S., Jafarian, Y., and Hajiannia, A.  Improvement of shallow foundations rested on saturated loose sand by zeolite-cement mixture: a laboratory study", Scientia Iranica, A, 25(4), pp. 2063-2076 (2018). DOI: 10.24200/SCI.2018.50153.1567.
16. ASTM D1194-72, Standard Test Method for Bearing Capacity of Soil for Static Load and Spread Footings, ASTM International, West Conshohocken, PA (1987).
17. Wood, D.M., Geotechnical Modeling, E. & F.N. Spon press, London (2004).
18. Jafarian. Y., Haddad, A., and Mehrzad, B. "Loadsettlement mechanism of shallow foundations rested on saturated sand with upward seepage", International Journal of Geomechanics, 17(3), pp. 1-14 (2016).
19. Vargas-Monge, W. "Ring shear tests on large deformation of sand", Ph.D Thesis, University of Tokyo (1998).
20. Bishop, A.W., Green, G.E., Garga, V.K., Andresen, A., and Brown, J.D. "A new ring shear apparatus and its application to the measurement of residual strength", Geotechnique, 21(4), pp. 273-328 (1971).
21. Iai, S. "Similitude for shaking table tests on soilstructure-fluid model in 1g gravitational field", Soils and Foundations, 29(1), pp. 105-118 (1989).
22. Towhata, I., Earthquake Geotechnical Engineering, Springer, Berlin (2007).
23. Otsubo, M., Towhata, I., Hayashida, T., Liu, B., and Goto, S. "Shaking table tests on liquefaction mitigation of embedded lifelines by backfill with recycled materials", Soils and Foundations, 56(3), pp. 365-378 (2016).
24. Vesic, A.S. "Analysis of ultimate loads of shallow foundations", Journal of the Soil Mechanics and Foundations Division, 99(1), pp. 45-73 (1973).
25. Skempton, A.W. and MacDonald, D.H. "The allowable settlement of building", In Proceeding in Institute of Civil Engineering, 5, pp. 727-768 (1956).