Estimation Numérique des facteurs de portance et d’influence de la forme des fondations superficielles

Abstract

The theoretical methods of the bearing capacity computations are all established for a strip footing resting on a semi-infinite homogeneous medium. These methods lead to the general formula of Terzaghi (1943), where the bearing capacity of shallow foundations is reduced to the determination of the bearing capacity factors, Nc, Nq et N. The effects of shape are taken in a semi-empirically manner by introducing factors of influence on the bearing capacity factors. Nevertheless significant divergences and deficiencies are observed by geotechnical practitioners. The finite difference code Flac was used in this thesis, to evaluate numerically the soil bearing capacity factors N’ for both smooth and rough ring and rectangular footings for low and high friction associated and non-associated Mohr-Coulomb soils. The results indicate a significant decrease in the value of N’ with an increase in the ratio of internal radius to external radius of the ring. For a rectangular foundation, the numerical computations show that the shape factor s is variable with the geometric ratio of the length to the width and the soil friction angle. The results also indicate that the soil dilation angle influences the value of N’ when the soil displays high non-associativity for large internal friction angle values. The values of N’ for a rough footing base, especially with greater values of φ, are shown to be significantly higher than those for a smooth footing base. The computational results are presented in the form of design tables and graphs, and compared with previous published results available in the literature.