Approach slabs

This chapter presents comprehensive information collected from available literature addressing the problem of the differential settlement at the bridge approach. General structural design considerations are presented in Section 17.1. In the second and third sections, general information on the definitions of the bridge approach and the bump at the end of the bridge and the tolerance of the bump are given. Thereafter, in the third section, the mechanisms causing the formation of the bump such as consolidation of foundation soil, poor compaction of the backfill material, poor water drainage and soil erosion close to the bridge abutments, types of bridge abutments, traffic volume passing over the bridge decks, age of the approach slab, the design of the approach slab, skewness of the bridge and seasonal temperature variations are mentioned and reviewed in detail. The fourth section presents maintenance measures normally employed by highway agencies to alleviate distressed approach slabs. Subsequently, a brief summary of the techniques used to mitigate the bump at the end of the bridge of the new bridge is presented.