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AN ESTIMATE OF THE INFLUENCE OF SOIL WEIGHT ON BEARING CAPACITY USING LIMIT ANALYSIS (1997)

An estimate of bearing capacity coefficient Ny for a strip footing is made using the kinematical approach of limit analysis. This approach leads to an upper bound on the true limit load when the calculations of the three terms in the bearing capacity formula are consistent with one collapse mechanism. However, as accepted in other proposals, the es­timate of the influence of the soil weight is calculated here separately from the terms dependent on the cohesion and the footing depth (overburden). It is conservative to take the minimum of each term in the bearing capacity formula, rather than minimum of the sum of the three terms. Coefficient Ny from such calculations becomes increasingly conser­vative (underestimated) with the increase in the soil cohesion and the footing depth. In view of using the upper-bound approach, such "all-minimum" procedure is prudent and appropriate for design. Results are given for both rough and smooth footings. A substantial influence of the dilatancy angle on Ny was found, and this is a reason for concern, since the non-associativity of plastic deformation of soils is usually not accounted for in design. Although calculations are numerical in nature, with optimization of the failure mechanism to obtain the best estimate, closed-form approxi­mations are suggested for practical purposes.

Reference:
SOILS AND FOUNDATIONS Vol. 37, No. 4, 57-64, Dec. 1997 Japanese Geotechnical Society
Organization:
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, USA
USA
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