Analyse numérique de l’influence de la stratification sur la portance des fondations superficielles

Abstract

The bearing capacity of foundations is a fundamental problem in geotechnical engineering, practically all theoretical work leading to the Terzaghi formula, where the bearing capacity of shallow foundations is reduced to determining the bearing capacity factors Nc, Nq and Ng. These factors raise a number of critics particularly for the bearing capacity factors Nc, N g and shape correction coefficients for the footings. All theoretical methods given bearing capacity have been established for a foundation sited on a semi-infinite homogeneous medium. But in the nature of such environments do not exist, because of their geological origin. Soils in contact with the base of the foundation are, in general, stratified and characterized by various natures and behaviours. Given the unavailability of exact theory of stratified soils and the variation of undrained cohesion with depth, the present research work focuses on numerical modelling, using software FLAC2D, on one hand the influence of stratification on the bearing capacity of shallow foundations and on the other hand the failure mechanisms. The numerical investigations are conducted on the following cases: · undrained clay with constant cohesion and linearly increasing cohesion with depth by varying the soil/foundation interface conditions (perfectly smooth and perfectly rough) and the increasing cohesion ratio with depth that cover all practical cases; · a two-layer undrained clay with constant cohesion with depth by varying the cohesion ratios, the ratio of the upper layer height at the base width of the footing and the soil/foundation interface conditions (perfectly smooth and perfectly rough) · a two-layer undrained clay with linearly increasing cohesion with depth by varying the ratio of the upper layer height at the base width of the footing, the cohesion ratios, the soil/foundation interface conditions (perfectly smooth and perfectly rough) and the increasing cohesion ratio with depth that cover all practical cases;