The use of geocell mattresses has proven to be an economic solution to the problem of constructing embankments over very soft ground. The combination of high tensile strength geogrid reinforcement erected into a 1.0 m deep cellular form and filled with granular material provides a stiff reinforced layer at the base of the embankment, permitting the maximum bearing capacity of the soft foundation soil to be mobilised. The paper describes the development of a Finite Element Model (FEM) for this type of construction and the results of a FEM analysis on a geocell reinforced embankment built over soft clay and peat at Dartford, England. Comparisons of data from field monitoring with that from the FEM analysis are also presented