68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

NUMERICAL STUDY FOR SOIL-SPRING STIFFNESS OF PILE GROUP

Lassaad Hazzar, Université de Sherbrooke (Canada)
Mourad Karray, Université de Sherbrooke (Canada)
Admir Pasic, Dessau Inc. (Canada)

Many approaches have been developed to determine the soil-spring stiffness and typical values have been proposed for different types and densities of soil. However, these typical values ignore the effect of the depth and the degradation of elastic parameter (G or E) as a function of strain. In this paper, a series of 3D numerical analyses are conducted to compute the equivalent soil-spring stiffness’s according to pile distortion for a pile group located under the central pier of bridge structure above the river Sault-au-Mouton (Longue-Rive, Quebec) and subjected to multi-loading conditions. In these simulations the degradation of the shear modulus is incorporated in order to account for soil nonlinearity. The idea is to develop equivalent springs that can be adapted to the lateral deformation of the pile. The stiffness of these springs thus varies depending on the distortion and may be adapted in an iterative process according to the pile deformation at each depth. This method can be compared to the linear equivalent method used in dynamic analysis where an equivalent shear modulus is adapted according to the shear distortion. In fact, This type of linear equivalent spring is very useful for structural engineers who want to incorporate the effect lateral capacity of soil in their models.