Journal of Geotechnical and Geoenvironmental Engineering · 1998 · 174 citations · 17 references
EngineeringCivil EngineeringFinite Element AnalysisGeotechnical EngineeringSoil MechanicsBearing CapacityFailure CriteriaFoundation StabilityShear StrengthShear Strength Of SoilsBearing Capacity AnalysisBearing Capacity FactorsBearing Capacity Of Strip FootingsCombined LoadingFailure EnvelopeFailure Envelope AnalysisStrip FootingsUndrained Stability
This paper applies numerical limit analyses to evaluate the undrained stability of surface footings on nonhomogeneous and layered clay deposits under combined vertical, horizontal, and moment loading. The authors use numerical limit analyses, employing linear programming and finite element discretization, to compute rigorous upper and lower bound solutions that resolve true collapse loads within ±5% for plane strain problems of surface footings on layered clay under combined loading. The analyses reveal that true collapse loads can be resolved within ±5%, that existing empirical bearing capacity factors for inclined, eccentric loading underestimate collapse loads by over 25% on homogeneous clay, become unreliable with significant undrained strength gradients, and that a numerically derived failure envelope can be approximated by simple curve‑fitting functions to update bearing capacity factors.
This paper applies numerical limit analyses to evaluate the undrained stability of surface footings on nonhomogeneous and layered clay deposits under the combined effects of vertical, horizontal, and moment (V, H, M) loading. The analyses are able to resolve the true collapse loads to within ±5% by computing rigorous upper and lower bound solutions for these plane strain problems using linear programming methods and finite element discretization. The results focus on the geometry of the three-dimensional failure envelope and illustrate the effects of underbase suction and non-homogeneous undrained strength profiles. The existing empirical bearing capacity factors for inclined, eccentric loading are conservative, often underestimating the exact collapse solutions for footings on homogeneous clay by more than 25%. However, the same correction factors can become completely unreliable when there is a significant undrained strength gradient. The numerically-derived failure envelope for footings on homogeneous clay is described approximately by curve fitting techniques using relatively simple functions that can be used to update the existing bearing capacity factors.
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