The study of earth pressure distribution on buried structures has a great practical importance in constructing
highway embankments above pipes and culverts. Based on Spangler’s research, the supporting strength of a conduit
depends primarily on three factors: 1. the inherent strength of the conduit; 2. the distribution of the vertical load and
bottom reaction; and, 3. the magnitude and distribution of lateral earth pressures which act against the sides of the
structure. Considering high fills above them and high earth pressures they may experience, rigid culverts are
usually used underneath highway embankments. To reduce high vertical earth pressures acting on a buried
structure, ultra-lightweight Geofoam will be placed above a culvert in the field, at Russell County, KY. Before
construction began, numerical analysis using FLAC 4.00 (Fast Lagrangian Analysis of Continua) had been
performed to predict stresses on the culvert. Results of the analysis show that Geofoam has a great effect in
reducing vertical stresses above and below the culvert. There are areas of high stress concentrations at the top and
bottom of the concrete culvert if no Geofoam was placed above the culvert. After placing Geofoam above the
culvert, the concentrated stress at the top can be reduced to 28 percent of the stress without Geofoam. The high
stress at the bottom of culvert can be reduced to 42 percent of the stress without Geofoam. Stresses on the two
sidewalls of the culvert were observed to have no significant change in values with and without Geofoam.