American Society of Civil Engineers


Simple Formulas for the Response of Shallow Foundations on Compressible Sands


by Nobutaka Yamamoto, (Engineer, Adv. Geomechanics, 4 Leura St., Nedlands, WA, 6009, Australia; formerly, Ph.D. Student, Centre for Offshore Foundation Systems, The Univ. of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. E-mail: nobutakay@ag.com.au), Mark F. Randolph, (Prof., Centre for Offshore Foundation Systems, The Univ. of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. E-mail: randolph@civil.uwa.edu.au), and Itai Einav, (Sr. Lect., The Univ. of Sydney, School of Civ. Engrg. J05, Sydney, NSW 2006, Australia. E-mail: I.Einav@civil.usyd.edu.au)

International Journal of Geomechanics, Vol. 8, No. 4, July/August 2008, pp. 230-239, (doi:  http://dx.doi.org/10.1061/(ASCE)1532-3641(2008)8:4(230))

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Document type: Journal Paper
Abstract: The engineering design of shallow foundations on sand is almost universally based on one of the variants of the classical bearing capacity formula. However, this formula is suitable only where the sand exhibits dilative behavior and a clear rupture mechanism forms at failure. The main challenge then is choosing a suitable friction angle, taking into account the soil density and the high stresses beneath the footing. When other conditions apply, in particular when the footing is large or founded on compressible materials, alternative approaches need more focus on soil compressibility. Two simple semianalytical formulas are proposed and explored in this paper: (1) an analysis using a one-dimensional (1D) compression equation; and (2) an analysis using the concept of “bearing modulus.” It is argued that the bearing modulus approach may be used for conditions that reflect moderate design parameters (i.e., moderate foundation size and sand compressibility), but for very large foundations or highly compressible soils the 1D compression method is found more suitable. It is shown that the bearing modulus analysis can be approached in terms of the compression response of the soil, suggesting a possible route to link the bearing modulus directly to the compression model parameters of the soil.


ASCE Subject Headings:
Calcareous soils
Compression
Load bearing capacity
Numerical analysis
Sand (soil type)
Shallow foundations