Scale and Boundary Effects in Foundation Analysis

by James Graham, Lectuer; Dept. of Civ. Engrg., Queen's Univ., Belfast, Northern Ireland,
John Gordon Stuart, Lectuer; Dept. of Civ. Engrg., Queen's Univ., Belfast, Northern Ireland,

Serial Information: Journal of the Soil Mechanics and Foundations Division, 1971, Vol. 97, Issue 11, Pg. 1533-1548

Document Type: Journal Paper


The bearing capacity of rough strip footings on sand is analyzed using numerical integration of the plasticity equations. The influence of different boundary conditions below the footing is studied for the zero surcharge case, and bearing capacity coefficients are calculated for various assumed settlements at failure. A pressure dependent solution is described which permits calculation of the variation of Φ with stress level in the failure zone. The results are compared with existing trial failure surface solutions and with experimental values. It is concluded that good agreement can be obtained between theoretical results which assume a trapped elastic wedge beneath the footing, and model results related to average Φ-values from triaxial tests in the normal range of cell pressures. The lack of agreement with field results and the computed variation of Φ in the failure zone imply that this relationship is empirical. A procedure is outlined for relating bearing capacity of a given-sized footing to the initial density of a sand using Φ versus pressure results from plane strain shear tests on sand at the same density.

Subject Headings: Footings | Failure analysis | Soil pressure | Load bearing capacity | Domain boundary | Foundations | Soil stress | Soil analysis

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