Evaluation of bridge approach settlement mitigation methods
Koutnik, Therese Ellen
Wisconsin Highway Research Program
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Over the past 20 years, extensive research has been conducted to study the causes and mitigation methods of bridge approach settlement or "the bump at the end of the bridge." Many Departments of Transportation are significantly impacted by bridge approach settlement, as it causes unsafe driving conditions, rider discomfort, poor public perception of the state infrastructure, structural failure of bridges, and long-term maintenance costs. The literature has indicated that poor performance of pavement, bridge abutment and type, consolidation of the backfill materials, consolidation of the foundation's soils, and poor drainage are contributors to bridge approach settlement. Many mitigation techniques have been used to control the settlement, but the methods selected depend on the specific site. Techniques to repair the bump include asphalt patching or overlays, slab jacking, and replacement of approach slabs. Because of the considerable amount of money spent on repairing the differential settlement, DOTs and the Federal Highway Administration (FHWA) have funded numerous studies to determine the causes, mitigation methods, and maintenance techniques of bridge approach settlement. This study is part of one of these studies, "Evaluation of Bridge Approach Settlement Mitigation," sponsored by the Wisconsin Department of Transportation. The purpose of this paper is to document the performance and effectiveness of two mitigation techniques, geosynthetic reinforced fill and flowable fill, installed behind four Wisconsin bridges. This study includes an extensive literature review, discussion of the field investigation, and performance evaluation of field results of these four bridges.