Seismic Bearing Capacity of Strip Foundations with Nonlinear Power-Law Yield Criterion Using the Stress Characteristics Method | Journal of Geotechnical and Geoenvironmental Engineering | Vol 148, No 11

AbstractThe computations of the bearing capacity of foundations have generally been carried out with the usage of the Mohr-Coulomb failure criterion—a linear yield envelope in a shear stress–normal stress plot. However, as noted from many experimental observations, the failure criteria associated with most geomaterials are generally nonlinear. A novel computational analysis, based on the stress characteristics method, has been performed in the current study to compute very accurately the seismic bearing capacity of a rough strip foundation considering a nonlinear power-law yield criterion. The analysis incorporates the effect of pseudostatic horizontal seismic inertial forces. The obtained results can, however, be used to include even the effect of the vertical component of the seismic inertial forces. The present formulation is based on the consideration of a curvilinear nonplastic trapped wedge below the footing base. By carrying out a detailed parametric analysis, the effects of different material shear strength parameters, overburden pressure, seismic forces, and foundation width on the bearing capacity factor Nσ have been examined. With the changes in horizontal seismic acceleration coefficients, the slip line patterns have also been explored. The results from the present analysis compare quite well with that reported from studies available in the literature.Practical ApplicationsWhile designing shallow foundations for a given structure, depending on the designed life of the structure, the values of the peak earthquake accelerations in horizontal and vertical directions can be estimated based on the geospatial location of the site and its past earthquake history. This manuscript provides the rigorous procedure and also establishes the design charts for determining the nondimensional bearing capacity factor in the presence of earthquake acceleration for the nonlinear power-law yield criterion; one of the primary advantage of implementing the nonlinear criterion is that it automatically incorporates the scale effects of foundations. By knowing the material parameters of the soil mass, applicable for the nonlinear power-law yield criterion, the ultimate bearing capacity of the foundation can accordingly be estimated from the established values of the bearing capacity factor in the presence of earthquake acceleration. The foundation of a given structure can, therefore, be designed by accounting for the reduction in the bearing capacity on account of pseudostatic earthquake inertial forces.

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