Numerical Analysis of an Arch Culvert beneath Imperfect Trench Covered with Geogrid Layers

The backfill above a high embankment culvert is over 10 m, which leads very large earth pressure on the crown of the culvert. The imperfect trench covered with geogrid method (ITG) was employed to reduce the vertical earth pressure on the crown. A series of numerical analyses were performed to investigate the effect of ITG on load reduction for the culvert. In the numerical simulations, the number of geogrid layers, the geometry shape and the dimension of the load reduction trenches, as well as the location and the stiffness of the overlaid geogrid were investigated to analyze the influences on the vertical earth pressures. The results show that the slope angle and the height of the trench, the plane stiffness of the geogrid have great effect on the efficiency of load reduction, trenches with higher height and slope angles of 90° lead to a significantly reduction on vertical earth pressure on the crown of culvert. The width of load reduction trench, the number of geogrid layers, the location and the spacing of the geogrids have negligible effect on load reduction, the results can provide references for load reduction of slab culvert.