The Analysis of Failure of a Normally Consolidated Clay Foundation Under Embankment Loading

Abstract

In this research an attempt is made to derive the following two approaches of arithmetic methods of evaluating ultimate bearing capacity of normally consolidated clay foundation subject to partial loading such as embankment with finite width. The two approaches are as follows: (1) Finite element deformation analysis of elasto-plastic clay foundation including consolidation behavior, and (2) Limit state analysis by rigid plastic finite element method. In the former analysis, the stiffness factor of clay foundation in terms of effective stresses is newly introduced, from which the definition of total failure of clay foundation is freshly made. In the latter analysis, stress induced anisotropy of undrained shear strength of clay is newly introduced so that the consistency be held between the limit analysis and load deformation analysis. Main conclusions obtained in the present study are as follows:(1)The solution of rigid plastic finite element analysis is shown to be very close to the solution obtained in a deformation analysis as far as undrained condition is concerned.(2)The effect of partial drainage expected during gradual load application is found to be less than 30% of undrained bearing capacity when the loading rate is within the range commonly used in engineering practice. The solution of rigid plastic finite element analysis is shown to be very close to the solution obtained in a deformation analysis as far as undrained condition is concerned. The effect of partial drainage expected during gradual load application is found to be less than 30% of undrained bearing capacity when the loading rate is within the range commonly used in engineering practice.