The construction of bridge approach embankments over soft clay deposits requires specialized geotechnical solutions, similar to highway embankment construction. Traditionally, bridges are founded on piles in order to prevent total settlements and ensure stability. In such cases, if no conventional ground improvement method is applied in the area where the approach embankment is to be constructed, differential settlements may develop between the bridge abutment and the approach embankment. In addition to increasing maintenance costs, these differential settlements may reach levels that could adversely affect the stability of both the embankment and the bridge abutment. To prevent such differential settlements and stability problems, bridge approach embankments can be constructed using geofoam blocks. As with conventional geofoam block roadway embankments, bridge approach embankments can be constructed either with a trapezoidal cross-section (Figures 1 and 2) or with vertical faces at ninety degrees to the horizontal (Figures 3 and 4). In addition to preventing differential settlements, the use of geofoam blocks in bridge approach embankments can reduce lateral earth pressures acting on the bridge abutment wall to negligible levels compared with conventional soil fill, thereby also providing economic benefits in the overall design of the bridge abutment.
In addition to constructing bridge approach embankments entirely with geofoam blocks, partial geofoam block layout configurations can also be implemented (Figure 5). Depending on local ground conditions, partial block layouts may be preferred where total and differential settlements remain within allowable limits, enabling the design of more economical bridge abutments under both static and dynamic loading conditions.
