Determination of deformations in earth dams constructed on soft soils by means of experimental and numerical analysis

ABSTRACT Deformations which may occur beneath embankments designed and constructed on soft soils can be generalized as vertical and horizontal deformations. When an embankment is constructed on a saturated cohesive soft soil, it is a necessity to perform a deformation analysis in order to investigate the immediate and time dependent vertical and lateral displacements which will occur in the soft ground. In this study, Alibey dam and the natural foundation soil have been numerically modelled by utilising finite element method. A coupled analysis tecnique has been carried out to investigate the stress-strain-consolidation behaviour of the soil ground by using the finite element method in which the presence of geological layers and the staged embankment loading are considered. Considering the each embankment loading stage individually stress increments, displacements and consolidation settlements that take place in the soil ground resulted from pore pressure increments occured after each stage of construction has been analysed depending on the length of time waited for the next loading during the construction stage. While there is a good agreement between the settlements computed from analysis and the settlements obtained from the field measurements, it is designated that the same consistency wasn't achieved considering the variations of lateral displacements and pore pressures. In order to determine the deformations by means of laboratory tests, reconstituted block samples were utilised. The strains were determined in the triaxial tests by measuring the vertical displacements that took place by conducting the vertical and horizontal effective principal stresses stage by stage on the prepared block samples under unisotropic conditions. The principal stresses applied to the samples were obtained from the non-linear elasto-plastic analysis which modelled the staged loading at site. The values of strains computed from the numerical model were found to be in close agreement with those of the laboratory measurements in all axes. Key Words : Soft soil, deformations, stress and strain, settlement, finite element method, coupled analysis, non-linear analysis. XVI