n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - The effect of global and partial factors of safety in bearing capacity calculations : technical paper

Volume 43, Issue 1
  • ISSN : 1021-2019



At first sight the change from a global safety factor to partial safety factors seems quite sensible and straightforward. This may well be so where the analyses to be used show a linear relationship between the parameters to be factored and the final result. However, in geotechnical analyses, this is frequently not the case and the application of partial safety factors to c' and f' will have further effects on other factors such as earth pressure coefficients and bearing capacity factors. This study has looked at one category of geotechnical analyses, namely bearing capacity analyses and has shown that the overall margin of safety, comparing actions with resistances, when using partial safety factors varies from about 1, 5 to about 4. While the use of partial safety factors can be argued to be better than the use of a single global safety factor, this large variation in overall margins of safety must be a cause for concern, given that the 'traditional' use of a global safety factor of about 3 has proved adequate in limiting failures to a frequency acceptable to society.

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