Abstract: The initial stress field of a precast slab culvert under the high embankment is simulated with a two dimensional finite difference model using FLAC3D software. The installation of the culvert as well as the embankment construction is also numerically simulated. Then, the load reduction efforts are simulated by placing the flexible fills on the top of culvert and improving the soil underneath the culvert. The results from the load reduction effort are compared with the initial stress field conditions. It is concluded that, with the increase of the thickness of flexible filling, the maximum stress coefficient, vertical soil pressures on the top as well as at the bottom of the culvert are nonlinearly reduced. No significant vertical load reduction effect is found from the soil improvement. With the increase of soil improvement depth, the vertical soil pressure at the bottom of culvert is decreased. However, the lateral earth pressures acting on the foundation soils are significantly increased.

Key words: Precast Slab Culverts, Numerical Simulation, Flexible Filling Materials, Soil Improvement, Earth Pressures