Western Iowa Missouri River Flooding -- Geo-Infrastructure Damage Assessment, Repair and Mitigation Strategies, TR-638, 2013

The 2011 Missouri River flooding caused significant damage to many geo-infrastructure systems including levees, bridge abutments/foundations, paved and unpaved roadways, culverts, and embankment slopes in western Iowa. The flooding resulted in closures of several interchanges along Interstate 29 and of more than 100 miles of secondary roads in western Iowa, causing severe inconvenience to residents and losses to local businesses. The main goals of this research project were to assist county and city engineers by deploying and using advanced technologies to rapidly assess the damage to geo-infrastructure and develop effective repair and mitigation strategies and solutions for use during future flood events in Iowa. The research team visited selected sites in western Iowa to conduct field reconnaissance, in situ testing on bridge abutment backfills that were affected by floods, flooded and non-flooded secondary roadways, and culverts. In situ testing was conducted shortly after the flood waters receded, and several months after flooding to evaluate recovery and performance. Tests included falling weight deflectometer, dynamic cone penetrometer, three-dimensional (3D) laser scanning, ground penetrating radar, and hand auger soil sampling. Field results indicated significant differences in roadway support characteristics between flooded and non-flooded areas. Support characteristics in some flooded areas recovered over time, while others did not. Voids were detected in culvert and bridge abutment backfill materials shortly after flooding and several months after flooding. A catalog of field assessment techniques and 20 potential repair/mitigation solutions are provided in this report. A flow chart relating the damages observed, assessment techniques, and potential repair/mitigation solutions is provided. These options are discussed for paved/unpaved roads, culverts, and bridge abutments, and are applicable for both primary and secondary roadways.

Regional Approach to Landslide Interpretation and Repair, TR-430, 2001

The objective of this report is to provide Iowa county engineers and highway maintenance personnel with procedures that will allow them to efficiently and effectively interpret and repair or avoid landslides. The research provides an overview of basic slope stability analyses that can be used to diagnose the cause and effect associated with a slope failure. Field evidence for identifying active or potential slope stability problems is outlined. A survey of county engineers provided data for presenting a slope stability risk map for the state of Iowa. Areas of high risk are along the western border and southeastern portion of the state. These regions contain deep to moderately deep loess. The central portion of the state is a low risk area where the surficial soils are glacial till or thin loess over till. In this region, the landslides appear to occur predominately in backslopes along deeply incised major rivers, such as the Des Moines River, or in foreslopes. The south-central portion of the state is an area of medium risk where failures are associated with steep backslopes and improperly compacted foreslopes. Soil shear strength data compiled from the Iowa DOT and consulting engineers files are correlated with geologic parent materials and mean values of shear strength parameters and unit weights were computed for glacial till, friable loess, plastic loess and local alluvium. Statistical tests demonstrate that friction angles and unit weights differ significantly but in some cases effective stress cohesion intercept and undrained shear strength data do not. Moreover, effective stress cohesion intercept and undrained shear strength data show a high degree of variability. The shear strength and unit weight data are used in slope stability analyses for both drained and undrained conditions to generate curves that can be used for a preliminary evaluation of the relative stability of slopes within the four materials. Reconnaissance trips to over fifty active and repaired landslides in Iowa suggest that, in general, landslides in Iowa are relatively shallow [i.e., failure surfaces less than 6 ft (2 m) deep] and are either translational or shallow rational. Two foreslope and two backslope failure case histories provide additional insights into slope stability problems and repair in Iowa. These include the observation that embankment soils compacted to less than 95% relative density show a marked strength decrease from soils at or above that density. Foreslopes constructed of soils derived from shale exhibit loss of strength as a result of weathering. In some situations, multiple causes of instability can be discerned from back analyses with the slope stability program XSTABL. In areas where the stratigraphy consists of loess over till or till over bedrock, the geologic contracts act as surfaces of groundwater accumulation that contribute to slope instability.

Bridge Deck Repair Using Epoxy Resin, HR-177, 1979

Research funds were approved for the purchase of equipment designed to proportion and inject epoxy resins into delaminated areas of bridge decks. Through investigation and refining of this process, it was anticipated that a maintenance procedure would be developed to delay spalling of bridge decks by "gluing down" delaminated areas before spalling occurred.

Engineering Fabric Repair Prior to Resurfacing - Roadglas - US 30, HR-525, 1992

In Iowa it is normal procedure to either use partial or full-depth patching to repair deteriorated areas of pavement prior to resurfacing. The Owens/Corning Corporation introduced a repair system to replace the patching process. Their Roadglas repair system was used in this research project on US 30 in Story County. It was installed in 1985 and has been observed annually since that time. There were some construction problems with slippage as the roller crossed the abundant Roadglas binder. It appears the Roadglas system has helped to control reflective cracking in the research areas. Since the time when this project was completed it has been reported that Owens/Corning has discontinued production of the Roadglas system.

Evaluation of Appropriate Maintenance, Repair and Rehabilitation Methods for Iowa Bridges, TR-429, 2003

Most states, including Iowa, have a significant number of substandard bridges. This number will increase significantly unless some type of preventative maintenance is employed. Both the Iowa Department of Transportation and Iowa counties have successfully employed numerous maintenance, repair and rehabilitation (MR&R) strategies for correcting various types of deficiencies. However, successfully employed MR&R procedures are often not systematically documented or defined for those involved in bridge maintenance. This study addressed the need for a standard bridge MR&R manual for Iowa with emphasis for secondary road applications. As part of the study, bridge MR&R activities that are relevant to the state of Iowa have been systematically categorized into a manual, in a standardized format. Where pertinent, design guidelines have been presented. Material presented in this manual is divided into two major categories: 1) Repair and Rehabilitation of Bridge Superstructure Components, and 2) Repair and Rehabilitation of Bridge Substructure Components. There are multiple subcategories within both major categories that provide detailed information. Some of the detailed information includes step-by-step procedures for accomplishing MR&R activities, material specifications and detailed drawings where available. The source of information contained in the manual is public domain technical literature and information provided by Iowa County Engineers. A questionnaire was sent to all 99 counties in Iowa to solicit information and the research team personally solicited input from many Iowa counties as a follow-up to the questionnaire.

Investigation of Improved Utility Cut Repair Techniques to Reduce Settlement in Repaired Areas, Phase II, TR-566, 2010

Trench maintenance problems are caused by improper backfill placement and construction procedures. This report is part of a multiphase research project that aims to improve long-term performance of utility cut restoration trenches. The goal of this research is to improve pavement patch life and reduce maintenance of the repaired areas. The objectives were to use field-testing data, laboratory-testing data, and long-term monitoring (elevation survey and falling weight deflectometer testing) to suggest and modify recommendations from Phase I and to identify the principles of trench subsurface settlement and load distribution in utility cut restoration areas by using instrumented trenches. The objectives were accomplished by monitoring local agency utility construction from Phase I, constructing and monitoring the recommended trenches from Phase I, and instrumenting trenches to monitor changes in temperature, pressure, moisture content, and settlement as a function of time to determine the influences of seasonal changes on the utility cut performance.

Identification of Practices, Design, Construction, and Repair Using Trenchless Technology, TR-570, 2010

Trenchless technologies are methods used for the construction and rehabilitation of underground utility pipes. These methods are growing increasingly popular due to their versatility and their potential to lower project costs. However, the use of trenchless technologies in Iowa and their effects on surrounding soil and nearby structures has not been adequately documented. Surveys of and interviews with professionals working in trenchless-related industries in Iowa were conducted, and the results were analyzed and compared to survey results from the United States as a whole. The surveys focused on method familiarity, pavement distress observed, reliability of trenchless methods, and future improvements. Results indicate that the frequency of pavement distress or other trenchless-related issues are an ongoing problem in the industry. Inadequate soil information and quality control/quality assurance (QC/QA) are partially to blame. Fieldwork involving the observation of trenchless construction projects was undertaken with the purpose of documenting current practices and applications of trenchless technology in the United States and Iowa. Field tests were performed in which push-in pressure cells were used to measure the soil stresses induced by trenchless construction methods. A program of laboratory soil testing was carried out in conjunction with the field testing. Soil testing showed that the installations were made in sandy clay or well-graded sand with silt and gravel. Pipes were installed primarily using horizontal directional drilling with pipe diameters from 3 to 12 inches. Pressure cell monitoring was conducted during the following construction phases: pilot bore, pre-reaming, and combined pipe pulling and reaming. The greatest increase in lateral earth pressure was 5.6 psi and was detected 2.1 feet from the centerline of the bore during a pilot hole operation in sandy lean clay. Measurements from 1.0 to 2.5 psi were common. Comparisons were made between field measurements and analytical and finite element calculation methods.

Timber Abutment Piling and Back Wall Rehabilitation and Repair, TR-616, 2012

Based on previous National Bridge Inventory data, the state of Iowa has nearly 20,000 bridges on low-volume roads (LVRs). Thus, these bridges are the responsibility of the county engineers. Of the bridges on the county roads, 24 percent are structurally deficient and 5 percent are functionally obsolete. A large number of the older bridges on the LVRs are built on timber piling with timber back walls. In many cases, as timber abutments and piers age, the piling and back wall planks deteriorate at a rate faster than the bridge superstructure. As a result, a large percentage of the structurally deficient bridges on LVRs are classified as such because of the condition of the timber substructure elements. As funds for replacing bridges decline and construction costs increase, effective rehabilitation and strengthening techniques for extending the life of the timber substructures in bridges with structurally sound superstructures has become even more important. Several counties have implemented various techniques to strengthen/repair damaged piling, however, there is minimal data documenting the effectiveness of these techniques. There are numerous instances where cracked and failed pilings have been repaired. However, there are no experimental data on the effectiveness of the repairs or on the percentage of load transferred from the superstructure to the sound pile below. To address the research needs, a review and evaluation of current maintenance and rehabilitation methods was completed. Additionally, a nationwide survey was conducted to learn the methods used beyond Iowa. Field investigation and live-load testing of bridges with certain Iowa methods was completed. Lastly, laboratory testing of new strengthening and rehabilitation methods was performed.