Minnesota Department of Transportation

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NS752: Bridge approach roadway embankment improvements

Problem

Per the FHWA, of the 600,000 US bridges, 25% have approach panel and roadway embankment settlement which costs $100 million a year to repair. MnDOT has foam jacked approach panels on 209 bridges over the past 2 years. While MnDOT has recently made updates to the reinforced concrete approach panel standards and associated drainage details, there is a business need to make improvements to bridge roadway embankments to reduce settlement.  The purpose of this research will be to evaluate new materials and methods that reduce approach roadway embankment settlement and recommend improvements to MnDOT standards that will reduce long term maintenance costs and increase pavement performance metrics.

The proposed scope of work will be to install, instrument, and evaluate the performance of a series of pilot projects consisting of the Penn DOT Geosynthetic Stabilized Bridge Approach (GSBA) standard, elasticized expanded polystyrene with geosynthetic wrap, and other identified technologies and methods. The research tasks will consist of a literature review, a synthesis of approach roadway embankment standards and best practices and their performance in other states, instrumenting pilot projects with earth pressure cells, settlement sensors, tiltmeters, and survey prisms, analysis, and recommendations.

Objective

This research is a priority because there is a technical and business need to make improvements to bridge roadway embankment standard plans and specifications to reduce settlement. The benefits to MnDOT and local agencies will be to understand the causes of bridge approach roadway settlement, identify which details, materials and construction practices best reduce approach roadway embankment settlement, update standard plans and specifications, improve roadway and bridge performance, and reduce long term maintenance costs.

Previous research

The project will build on this research by instrumenting and measuring technologies incorporated into actual bridge approach embankments and by measuring the performance of materials and geotechnologies incorporated into actual bridge approach embankments. 

  • Bridge Approach Settlement and its Mitigation Schemes: A Review.
    • Prakash, Bhaskar; Tiwari, Anoop Kumar; Dash, Suresh R. Bridge Approach Settlement and its Mitigation Schemes: A Review. Transportation Research Record: Journal of the Transportation Research Board, Volume 2678, Issue 8, 2024, pp 660-689
    • https://trid.trb.org/view/2341475
    • Abstract: The primary function of the bridge approach is to provide a seamless transition from the highway or railway embankment to the bridge structure. However, a sudden change in elevation (drop/bump) at the transit of these two has often been observed. This sudden drop/bump acts as a potential cause for motorist discomfort, impact on the bridge deck, and cracks on the pavement surface. This phenomenon of ground settlement or deformation that can occur near the approach or abutment of a bridge for various reasons is often referred to as bridge approach settlement (BAS). Several researchers have contributed to formulating the reasons behind BAS and have proposed several mitigation techniques. This manuscript provides a comprehensive literature review on the causes of BAS, the contribution of various research works on mitigation techniques, and experimental, numerical, and field studies of various BAS mitigation schemes. The causes and mitigation techniques are categorized based on major components of the bridge structure, that is, the foundation, abutment, backfill soil, bridge approach, and bridge deck interface. Each of these mitigation schemes has advantages and disadvantages, and the best approach will depend on several factors, such as the type of soil, the loading conditions, and the design of the bridge and its approaches. The feasibility of various mitigation schemes is also reviewed with respect to their efficacy and ease of use.
  • Loading and Wetting-induced Settlement of Bridge Approach Embankment Materials in Utah.
    • Lawton, Evert; Maringanti, Sai Sravan; Jones, Adam C. Loading and Wetting-induced Settlement of Bridge Approach Embankment Materials in Utah. University of Utah, Salt Lake City; Mountain-Plains Consortium; Office of the Assistant Secretary for Research and Technology, 2024, 219p
    • https://trid.trb.org/view/2494752
    • Abstract: Often engineers and maintenance personnel are faced with a serious problem in the maintenance of bridges due to excessive settlement of approach embankments near bridge abutments, causing bumps at the ends of the bridges. These settlements result from loading-induced and sometimes wetting-induced strains within the native material at the site caused by the weight of the embankment and loading and wetting-induced strains within the embankment material itself. The primary objectives of this research were to (a) determine the loading-wetting stress-strain properties of 10 selected embankment materials under varying conditions of density, load, and moisture; (b) identify potential problems for each type of embankment material in terms of contributing to settlement that may exacerbate the “bump at the end of the bridge” problem; and (c) recommend changes to Utah Department of Transportation specifications for embankment materials used in bridge approaches. These objectives were achieved by conducting one-dimensional compression-wetting tests on compacted specimens of the materials using standard and larger consolidometers. Based on results and analyses from these tests, recommendations were made to change the current specifications regarding grain-size distribution, plasticity of the materials; shape of the particles; moisture condition during processing, transport, and compaction; allowable compaction during freezing or snowy conditions, and the method used for quality control.

Expected outcomes

  • New or improved technical standard, plan, or specification

Expected benefits

The numbers 1 and 2 indicate whether the source of the benefit measurement is from: 

  1. A specific research task in your project that will be measuring this particular benefit, or
  2. A separate effort to analyze data provided by the state or local agency involved in this project.
  • Decrease Lifecycle Costs: (2)
    • Measure the longer life of the bridge approach embankments and subtract this from the initial costs in the LCCA. 
  • Environmental Aspect: (2)
    • Track this by multiplying the longer life of the bridge approach embankments by the yearly unit environmental costs.
  • Increase Lifecycle: (2)
    • Measure the longer life of the bridge approach embankments and subtract this from the initial costs in the LCCA. 
  • Operation and Maintenance Saving: (2)
    • Estimate the reduction of long-term maintenance costs through improved bridge roadway embankment standard plans and specifications that reduce settlement.
  • Safety: (2)
    • Measure the longer life of the bridge approach embankments and multiply this by associated safety costs.
  • User Benefits: (2)
    • Track the increases in the Ride Quality Index (RQI) for the areas where the bridge approach embankment improvements are installed.
  • Risk Management: (2)
    • Track decreases in crashes and vehicle maintenance due to less bump at the end of the bridge.

Technical advisory panel

  • Joe Nietfeld - OMRR
  • Ceren Aydin - OMRR
  • Raul Velasquez - OMRR
  • Dave Conkel or Brian Homan - Bridge Office State Aid
  • Braden Cyr - Bridge Office Standards