NCHRP Implementation Support Program. Implementation of NCHRP Research Report 887 - Guidance for Underwater Installation of Filter Systems

In the United States, bridge scour — or the erosion of soil or sediment around abutments and piers — is one of the leading causes of bridge failure. During the construction of a bridge, countermeasures are taken to prevent this erosion. However, small soil particles can still pass through voids and gaps in the countermeasure structure. To prevent this additional erosion through the countermeasure, a filter should be placed between the countermeasure and the underlying soil. Despite the importance of including filters in the construction of countermeasures, a survey of bridge projects showed that few bridges in the U.S. include them due to constructability or environmental concerns. The goal of the original research undertaken by Ayres Associates on behalf of NCHRP was to provide guidance on the process for installing these filter systems, addressing common concerns and issues that prevent their inclusion (NCHRP Project 24-42, Research Report 887). In it, the research outlines the ways in which filters— both granular and geotextile filters — can be installed under different construction conditions. The research examined a number of approaches using these two methods: (1) Loose granular filter (placed either by clamshell or tremie, not dumped) and (2) Geotextile fabric by itself (typically placed by divers and temporarily secured by sandbags, steel frame, or pins): self-sinking mat (machine-placed), self-sinking mat (diver-placed), pre-filled geocontainers, diver-filled geocontainers, and geotextile affixed to armor. In cases using the loose granular filter and geotextiles, many approaches used certified divers to conduct the installation, giving greater flexibility and control over the process. Divers were responsible for filling geocontainers, guiding self-sinking mats, or placing granular materials using a tremie or clamshell depending on the method. The main considerations in determining which materials and methods to use were the access to the site and clearance (e.g. if the filter to be placed under a pier), the depth of the placement, and the velocity of the flowing water. After installation of any filter type and the armor layer is placed on top of the filter, there is no maintenance required unless the armor layer is damaged (for example during a flood event). As part of the project, Ayres Associates produced an implementation document, Training Manual for Underwater Installation of Filter Systems which formed the basis of the implementation work conducted as part of this project 24-44. Using this training manual as the foundation, Ayres Associates worked with NCHRP to plan a one-day workshop on October 10, 2019, in Fort Collins, CO. Over 60 different state departments of transportation (DOTs) were invited to participate in the workshop, and ultimately representatives from 16 DOTs attended along with two consultants, and a representative from the Federal Highway Administration (FHWA). Over the course of the workshop, participants learned about the purpose and importance of filters, approaches for their installation, and best practices and recommendations from NCHRP research. At the conclusion of the educational sessions of the workshop, participants had the opportunity to work through a problem-solving session using a real-world case study, where they could apply the knowledge learned earlier in the workshop. Attendees were provided the resources (the Instructor’s Guide, the Power Point® presentation, and a brief video) and the knowledge to return to their agencies and provide essential training on underwater installation of filters to their associates, consultants, and contractors.

Language

  • English

Project

  • Status: Completed
  • Funding: $50000
  • Contract Numbers:

    Project 20-44(14)

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Mohan, Sid

  • Performing Organizations:

    Ayres Associates

    ,    
  • Principal Investigators:

    Clopper, Paul

  • Start Date: 20190325
  • Expected Completion Date: 20200324
  • Actual Completion Date: 20200324

Subject/Index Terms

Filing Info

  • Accession Number: 01712952
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-44(14)
  • Files: TRB, RIP
  • Created Date: Jul 29 2019 3:26PM