Thesis (M.Eng.) - Asian Institute of Technology, 1992

A Thesis submitted in partial fulfillment of the requirements for · the degree of Master of Engineering, School of Engineering and Technology

The settlement and the stability are the primary geotechnical considerations involved in the design of an embankment founded on soft clay. This study includes an analysis of settlement characteristics for trial embankments, resting on soft clays, with and without treatment. The Field Deformation Analysis (FDA), a simple concept dealing with lateral and vertical deformation characteristics of soft foundation, is employed to predict the settlement components of an embankment foundation during the loading and the consolidation stage. Immediate, consolidation and creep components of settlement are delineated and quantified during loading and consolidation. These settlement components are then compared with the results obtained from the Finite Element Method (FEM) of analysis. The FEM analysis is performed using CRISP computer program, which bears many soil constitutive models, the modified Cam-clay model inclusive. FEM analysis is also performed to predict the behaviour of an embankment provided with geogrid and vertical drains. The simple approach, achieved by modelling the geogrid using strain compatibility and equilibrium conditions, is found to offer results confinning to and quite in concurrence with the field behaviour. Two different models were studied to incorporate 3-D axisymetric behaviourofdrains into 2-D plane strain condition in theembankment analysis.Basedon comparison studies made with field measurements, an appropriate vertical model is recommended for plane strain analysis. Finally, a simple design chart for embankment constructions, based on the results obtained from the analysis of untreated embankments, is presented. A simple computer programme based on the above mentioned chart is also prepared.