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 com pressible and the bridge deck is essentially rigid. This causes a ''bu mp'' to form at the approach abutment, and so many bridges are provide d with approach slabs, the purpose of which is to span across any diff erence in level caused by differential settlement between the embankme nt and the bridge. Repeated traffic loadings can, however, produce a n ew bump at the end of the slab. To overcome this problem, approach sla bs can be constructed at an angle to the horizontal, sloping down bene ath the pavement. The varying thickness of base course above the slab produces a graded deformation in the pavement and results in a smoothe r riding surface. Model pavements and approach slabs have been tested in a laboratory-scale test track, and these tests have shown the effec tiveness of sloping approach slabs in reducing the problem of a bump f orming at the end of the slab.