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Research conducted by Center for Earthworks Engineering (CEER), Iowa State University

Western Iowa Missouri River Flooding Geo-Infrastructure Damage Assessment, Repair and Mitigation Strategies. Research conducted by Center for Earthworks Engineering (CEER), Iowa State University. 2014 AASHTO High Value Research Peggi Knight. Problem:.

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Research conducted by Center for Earthworks Engineering (CEER), Iowa State University

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  1. Western Iowa Missouri River FloodingGeo-Infrastructure Damage Assessment, Repair and Mitigation Strategies Research conducted by Center for Earthworks Engineering (CEER), Iowa State University 2014 AASHTO High Value Research Peggi Knight

  2. Problem: • Full year’s worth of rainfall in one month. • More than 200% above normal snowpack in Rockies. • Longest duration flood event in US History. • At the height of the flooding a 75-mile stretch of Missouri River had no open crossing in Iowa. • At some locations in Iowa water flowed several feet deep over roadways for more than four months. • Approximately 60 miles of IA state and interstate highways and over 100 miles of county (secondary) roadways were closed.

  3. Problem: Office of Research and Analytics • Obvious Damage • Stripped overlays • Delaminated Surfaces • Understanding the damage we can not see • Unknown voids • Damage to bridge foundations and culverts • Determining when to open roads up to traffic • Saturated embankments

  4. Research Performed: • Objectives • Asses the damage to the geo-infrastructure on affected local roadways • Develop effective repair and mitigation strategies • Develop emergency response criteria • Develop a guide for flood damage assessment for future flood events

  5. Western Iowa Missouri River Flooding • Tests to evaluate roadway support capacity, embankment conditions, and settlement problems • GPR, FWD, DCP • Soil shear strength • Shelby tube samples for lab analysis • Monitor performance of the flooded versus un-flooded areas by evaluating subsurface foundation layer performance characteristics over time. • Visual flood water boundaries (aerial images, dead grass, damage to gravel surfaces, shoulders and chip seals) do not equate to saturated roadway embankment limits. • Water flow through the road foundation layers – erosion, consolidation, creation of weep holes.

  6. Western Iowa Missouri River Flooding Google images were used to help identify flood boundaries by comparing pre-flood (6/28/2010) imagery and during flood (7/17/2011) images

  7. Western Iowa Missouri River Flooding Weep holes (approx. 4 in.) found at one culvert inlet. Similar weep holes found at other culverts. Some culverts had as many as 20 weep holes.

  8. Western Iowa Missouri River Flooding FWD plate depression at one of the test segments

  9. Research Results • FWD testing of some locations showed up to a 52% decrease in modulus – DCP testing showed it is due to loss of foundation support. • Field testing identified differences in road support conditions in flooded versus un-flooded areas (saturated vs. unsaturated). • The FWD and DCP tests provided valuable subsurface information to characterize support conditions. • Understanding the performance differences between flooded versus un-flooded road segments based on engineering measurements could be useful as part of the process to define and prioritize areas for repair.

  10. Research Results • Catalog of field assessment techniques, descriptions and guidance • 20 potential repair/mitigation solutions with descriptions and guidance • Flow chart relating damages observed, assessment techniques, and potential solutions These options are discussed for paved and unpaved roads, culverts, and bridge abutments.

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