Effect of Orientation of Approach Slabs on Pavement Deformation

Differential settlements often occur between bridge abutments and the approach embankments either because the soil underlying the embankment consolidates or because the pavement and embankment materials are compressible and the bridge deck is essentially rigid. This causes a “bump” to form at the approach abutment, and so many bridges are provided with approach slabs, the purpose of which is to span across any difference in level caused by differential settlement between the embankment and the bridge. Repeated traffic loadings can, however, produce a new bump at the end of the slab. To overcome this problem, approach slabs can be constructed at an angle to the horizontal, sloping down beneath the pavement. The varying thickness of base course above the slab produces a graded deformation in the pavement and results in a smoother riding surface. Model pavements and approach slabs have been tested in a laboratory‐scale test track, and these tests have shown the effectiveness of sloping approach slabs in reducing the problem of a bump forming at the end of the slab.