Several Comments on Influence Zone Depth Progress in Deep Hole Foundations

摘要

The paper presents analytical and numerical approaches to the evaluation of the depth of the influence zone; the term influence zone is assigned to the region where the load has substantial influence on the deformation of the soil skeleton. The approach relies on the analytical solution based on the analysis of Westergard subspace assuming elastic material response. The depth of the influence zone must also be taken into account in the back analysis of the soil parameters, e.g. the deformation modulus. The necessity of this is shown by rigid plate field load tests. The standard back analysis based on the Boussinesq half space theory provides unreal data when the load of the plate is not sufficient and the depth of influence zone is small. It is caused by geostatic stress. Due to excavation (e.g. in the deep hole) the soil is significantly over-consolidated and the small surcharge deforms only thin upper layer of the subsoil. Boussinesq formula should be accepted if the depth of influence zone reaches approximately two and half times higher than width of footing.