Bearing Capacity on Drained Subsoil
One of the following approaches is available to assess the bearing capacity of a foundation if drained conditions are assumed:
- according to CSN 73 1001 "Základová pùda pod plošnými základy" approved 8.6. 1987
- according to Polish standard PN-81 B - 03020 "Grunty budowiane, Posudowienie bezpošrednie budowli, Obliczenia statyczne i projekktowanie" from year 1982
- according to Indian standard IS:6403-1981 "Code of Practice for Determination of Bearing Capacity of Shallow Foundations" from year 1981
- according to EC 7-1 (EN 1997-1:2003) "Design of geotechnical structures - Part 1: General rules"
- according to NCMA Segmental retaining walls manual, second edition
- according to Chinese standard GB 50007-2002
- according to Russian standard SNiP 2.02.01-83
- according to Danish standard DS/EN 1997-1 DK NA:2013
- according to DPWH standard "Design Guidelines, Criteria and Standards: Volume 2C – Geological and Geotechnical Investigation - Annex G: Geotechnical Formulas"
All approaches incorporate coefficients due to Brinch - Hansen (see) to account for inclined ground surface and inclined footing bottom.
Assuming drained conditions during construction the soil below spread footing deforms including both shear and volumetric deformations. In such a case the strength of soil is assumed in terms of effective values of the angle of internal friction φef and the effective cohesion cef. It is also assumed that there is an effective stress in the soil equal to the total stress (consolidated state). Effective parameters φef, cef represent the peak strength parameters.
Owing to the fact that the choice of drained conditions depends on a number of factors (rate of load, soil permeability, degree of saturations and degree of overconsolidation) it is the designer's responsibility to decide, depending on the actual problem being solved, if the effective parameters should be used.
During seismic analysis, the program performs the calculation of bearing capacity for both cases - with and without. The resultant bearing capacity is lower from these two values.