Literature Review of Causes and Mitigation Techniques for Bumps at Ends of Bridges
Hao Liu, Jie Han, Saif Jawad, Robert L. Parsons
Abstract
Bridges supported by abutments on rock or end-bearing piles are not expected to settle. However, sometimes approach embankments to bridge abutments settle due to underlying compressible soil and/or traffic loading, causing bumps at the ends of bridges resulting from differential settlement between abutments and embankments. Climatic conditions including temperature changes and heavy rainfalls may also cause bumps. The seasonal temperature change generates expansion and contraction on bridge girders, which induce soil movements in the backfill behind the abutments. Heavy rainfall may cause erosion in the backfill when drainage systems are insufficient. In addition, improper design and construction may end with settlement of the backfill. This paper provides a comprehensive literature review and summarizes the internal and external reasons and mitigation techniques for bumps at the ends of bridges. The mitigation techniques are classified into five categories and compared in terms of their advantages and disadvantages: (1) bridges on shallow foundations supported by geosynthetic-reinforced soil (GRS); (2) use of lightweight fill; (3) use of approach slabs to create a smooth transition between bridges and embankments; (4) improvement of soft soils underneath embankments; and (5) stabilization of embankment fill.