RES2019-22: Geosynthetic Reinforced Soils for Bridge Approach Slab Support

Two approach slabs are constructed at bridge ends to serve as a smooth transition from the highway pavement to the bridge deck. Motorists usually complain about a sudden change in elevation (bump) at the highway/approach slab (H/S) joint that causes a potential hazard for public safety, damage to vehicles, and riders’ discomfort. Many US States conducted research to solve the problem of bridge bumps with mixed degrees of success. In this project, the finite element (FE) method was used to predict the differential settlement at the H/S joint when supported by a strip footing (sleeper slab) that sits on compacted layers of soil embankment with geogrid reinforcement. A parametric study was conducted to select the optimum design which consists of 4 geogrid layers and a layer of woven polypropylene geotextile to separate the embankment clay from the reinforced aggregate fill. The geogrid layers are equally-spaced within a depth of 2 × B below the strip footing, where B is the width of the footing. The inclusion of geogrid reinforcement did not only enhance the ultimate bearing stress of the strip footing but also redistributed the vertical loads over a wider region of soil embankment and thus reduced settlement. A case study is also presented for modeling the performance of a design recommended by the Tennessee Department of Transportation (TDOT) for the retrofit of the bridge ends. The recommended design suggests replacing soil embankment underneath the approach slab with 4 biaxial geogrid layers between 9-inch thick lifts of openly graded aggregate and a layer of woven polypropylene geotextile to separate the embankment clay from the reinforced aggregate fill. The approach slab has a length of 24 ft and a thickness of 1 ft supported by a 3 ft sleeper slab (B = 3 ft) with a thickness of 1 ft.

• Record URL:
  https://www.tn.gov/content/dam/tn/tdot/long-range-planning/research/final-reports/res2019-final-reports/RES2019-22_Final%20Report_Approved.pdf

Language

• English

Project

• Status: Completed
• Funding: $100000
• Contract Numbers:

  RES2019-22

• Sponsor Organizations:

  Tennessee Department of Transportation

  James K. Polk Building
  Fifth and Deaderick Street
  Nashville, TN  United States  37243-0349
• Managing Organizations:

  Tennessee Department of Transportation

  James K. Polk Building
  Fifth and Deaderick Street
  Nashville, TN  United States  37243-0349
• Project Managers:

  Kniazewycz, Ted

• Performing Organizations:

  University of Tennessee, Knoxville

  Knoxville, TN  United States 
• Principal Investigators:

  Alshibli, Khalid

• Start Date: 20190501
• Expected Completion Date: 20220228
• Actual Completion Date: 0
• USDOT Program: Transportation, Planning, Research, and Development

Subject/Index Terms

• TRT Terms: Bridge approaches; Bridge design; Geosynthetics; Mechanically stabilized earth; Slabs
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways;

Filing Info

• Accession Number: 01771488
• Record Type: Research project
• Source Agency: Tennessee Department of Transportation
• Contract Numbers: RES2019-22
• Files: RIP, STATEDOT
• Created Date: May 11 2021 5:57PM