This spreadsheet performs shallow foundation design using data from the Standard Penetration Test. Various methods are used for the bearing capacity criterion and the settlement criterion (serviceability). The program was developed as part of a research on the reliability of the use of SPT in the shallow foundation design.
Bearing Capacity Criterion
Method 1: Terzaghi bearing capacity equation
The SPT blowcount is correlated to the friction angle. Two correlations are used: The Schmertmann (1975) and the Hatanaka and Uchida (1996). These methods are based on actual data and take into account the effect of the overburden stress. The more traditional recommendations (Peck et al. 1984, Meyerhof 1956) are not used in this program as the use of the Standard Penetration Test has improved since then.
Method 2: Meyerhof (1965)
This is a simple empirical equation provided by Meyerhof and is in general very conservative.
The Burland and Burbdige (1984) method is used, which was considered by the author as the most reliable method to date. The N value in this method is the average N value over the depth of influence below the footing, approximately, 1.5 times the width of the foundation. This is a statistical method, and for that reason, the mean + sigma and mean - sigma ranges are also shown.
Corrections need to be made in the SPT blowcount, according to the recommendations of Youd et al (2001), for the type of sampler, the rod length, the borehole diameter, the energy transmitted to the sampler and the overburden stress.
Burland, J.B., Burbidge, M.C. (1984), Settlement of foundations on sand and gravel, Proceedings of the Institution of Civil Engineers, Part 1, 1985, 78, Dec., 1325-1381.
Hatanaka, M., Uchida, A. (1996). Empirical correlation between penetration resistance and effective friction of sandy soil. Soils & Foundations, Vol. 36 (4), 1-9, Japanese Geotechnical Society.
Mayne, P.W. (2001), Geotechnical site characterization using Cone, piezocone, SPTu, and VST, Civil and Environmental Engineering Department, Georgia Institute of Technology
Meyerhof, G.G. (1956), Penetration tests and bearing capacity of cohesionless soils, Journal of the soil mechanics and foundation division, ASCE, Vol. 82, No. SM1, January, pp. 1-19.
Schmertmann, J.H. (1975), Measurement of insitu shear strength, keynote lecture, Proceedings of the conference on in-situ measurement of soil properties, June 1-4, 1975, vol. II, American Society of Civil Engineers.