Management of water and backfill characteristics for improved bridge approach performance

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2004-01-01
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Mekkawy, Mohamed
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Bridge approach settlement is a problem that draws upon resources for maintenance and repair, causes damage to vehicles, and creates a negative perception of the transportation agency. To alleviate bridge approach settlement, erosion and soil collapse must be reduced. This can be accomplished by improving water management around bridges and backfill characteristics. The purpose of this study was to examine the effects of improved water management and backfill properties on settlement of bridge approaches and to recommend new alternatives for design, construction, and maintenance of new and existing bridge approaches. Furthermore, recommend a threshold limit for approach slab settlement as a criterion to initiate maintenance. The objectives of this research are a literature review of relevant research of practices of other states, field inspection of existing and under construction bridges, monitoring of maintenance practices, laboratory experiments to analyze the properties of various backfill materials and geosynthetic drainage materials, and developing a new rating system as a criterion to initiate maintenance. To analyze the characteristics of backfill materials, the collapse index test was performed to measure the change in volume of the different backfill materials upon saturation at different moisture contents. Vibrating table tests (ASTM D4253-00) were performed, and a one-fourth scale model of a bridge approach was constructed in an effort to evaluate geosynthetic drainage materials as well as a variety of drainage details. This study reveals that poor water management is a major cause of bridge approach problems. Further, granular backfill materials placed within the bulking moisture content range are susceptible to collapse upon saturation. Proper compaction of granular backfill materials and placing porous backfill around subdrains is not being followed during construction. Grouting behind abutments and resurfacing of approach slabs do not necessarily prevent further settlements. The URETEK Inc. maintenance method appears to be a successful alternative to conventional maintenance practices; however, the long term performance is yet to be verified. The constructed model illustrated that using porous backfill, geocomposite vertical drain, and tire chips improved the bridge approach performance. The bridge Approach Index parameter and the IRI data were used as a new rating system.

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Thu Jan 01 00:00:00 UTC 2004
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