County Road 55 over Minnesota Southern Railway

<figure id='attachment_8133' style='max-width:927px' class='caption aligncenter'><img class="size-full wp-image-8133" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the completed County Route 55 Bridge over Minnesota Southern Railway." width="927" height="459" /><figcaption class='caption-text'> Figure 1. Completed County Route 55 Bridge over Minnesota Southern Railway. Source: MnDOT.</figcaption></figure>Location: Rock County, Minnesota Owner: Rock County Year Constructed: 2013 National Bridge Inventory (NBI) Number: 67564 Crossing Type: Roadway bridge over railroad Superstructure Type: Concrete Girders Span: 78 feet Maximum Wall Height: 26 feet Maximum Wall Face Width (edge to edge): 39 feet Skew: 0 degrees Facing Type: Concrete Masonry Units (CMU) Average Daily Traffic (ADT) (when constructed): 135 Contract Type: Design-Bid-Build Unique Project Feature: GRS-IBS bridge with the steepest grade (5.3 percent) at the time of construction; the first GRS-IBS bridge in MinnesotaBackground: Surrounded by farmland, County Route 55 over Minnesota Southern Railway (CR-55 Bridge) is located three miles east of the city of Luverne in Rock County, Minnesota (see figures 2a and 2b). Rock County is situated in the southwest corner of Minnesota and borders Iowa and South Dakota. The CR-55 Bridge serves as a grade separation between the railroad and the roadway, provides an important access point to Interstate 90, and connects local communities. Minnesota Southern Railway has a long history in the region. The railroad is primarily used for transporting agricultural goods and depends on high crop yields which can vary from year to year. Today, the tracks remain active and serve trains on a weekly basis.<figure id='attachment_8137' style='max-width:1155px' class='caption aligncenter'><img class="size-full wp-image-8137" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Sketches of the project location, to the left, location of Rock County, Minnesota. To the right, location of CR-55 Bridge." width="1155" height="582" /><figcaption class='caption-text'> Figure 2. (a) Location of Rock County, Minnesota and (b) CR-55 Bridge. Source: Open Street Map, ESRI, FHWA.</figcaption></figure>Prior to being replaced, the CR-55 Bridge over Minnesota Southern Railway Bridge was a timber structure (see figure 3) and had been closed for two decades due to its deteriorating condition and a lack of funds for replacement. Due to its cost efficiency and ability to reduce construction time, Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) was selected to construct the new bridge. The bridge replacement was a coordinated effort between the Minnesota Department of Transportation (MnDOT), Federal Highway Administration (FHWA) and Rock County Department of Highways.Deployment: MnDOT engineers found out about GRS-IBS technology from a showcase hosted by the Wisconsin Department of Transportation (WisDOT) in 2012. The design team included FHWA, the project’s engineering consultant, and MnDOT. As the project was the first GRS-IBS bridge in the state, engineers relied heavily on the design guidelines developed by FHWA.<figure id='attachment_8138' style='max-width:932px' class='caption aligncenter'><img class="size-full wp-image-8138" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the old CR-55 Bridge." width="932" height="687" /><figcaption class='caption-text'> Figure 3. The old CR-55 Bridge. Source: MnDOT.</figcaption></figure>The new CR-55 Bridge was proposed in the same location as the old bridge. The old timber bridge was demolished and removed many years prior to the start of replacement efforts in 2013. The fill abutments of the old bridge, however, remained in place. The old fill abutments proved helpful as they had preloaded soil which improved bearing capacity and reduced total settlements. The new CR-55 Bridge featured abutment walls up to 26 feet high built with Concrete Masonry Unit (CMU) blocks and a 78-foot span provided by precast concrete girders as the bridge’s superstructure (see figure 4). The width of the bridge was 33 feet and the average daily traffic (ADT) was 135.<figure id='attachment_8135' style='max-width:1024px' class='caption aligncenter'><img class="size-full wp-image-8135" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the construction of GRS abutment with CMU blocks." width="1024" height="768" /><figcaption class='caption-text'> Figure 4. Construction of GRS abutment with CMU blocks. Source: MnDOT.</figcaption></figure>The most unique feature of the CR-55 Bridge was a 5.3 percent grade – the steepest for GRS-IBS bridges at the time of construction. Such a steep grade was required to provide sufficient clearance for the passing trains. This unique feature led to the project’s acceptance into FHWA’s GRS-IBS Research Evaluation Program; the program’s objective is to expand the use of GRS-IBS by evaluating and optimizing the technology. To explore the potential effects of 5.3 percent grade on the bridge performance, an instrumentation plan was developed by FHWA with the help of the project team. Funding for the instrumentation program was also provided by FHWA.Project Challenges and Solutions: The CR-55 Bridge was a successful project that demonstrated the strong potential of GRS-IBS technology in the state of Minnesota. The challenges described below are not unique to the GRS-IBS technology and are primarily related to the bridge’s extensive monitoring program.Snow Minnesota weather slightly disrupted the project schedule. The spring snowstorms that moved through Rock County in April resulted in delayed construction start including the delay of the installation of the instrumentation. This caused a postponement of a showcase, originally planned for May 2, 2013. Since the block placement work was yet to start at that point, the showcase was rescheduled for June 6, when the abutments would be completed and the concrete girders installed. Despite the delay, timely coordination between showcase organizers and participants ensured that the event was a success. The video from the showcase can be found <a href="https://www.youtube.com/watch?v=QWkREPlQXZ0">here</a>.Instru… installation and maintenance While most aspects of the instrumentation have been successful, funding, installation, and long-term support have been a challenge. To reduce instrumentation costs, two repurposed Traffic Management Center cabinets were used to house batteries, communication systems, data collection hardware, power regulators, and any associated wiring and equipment (see figure 5). The instrumentation was installed by several different crews, and this made it challenging to collect all the sensor information in one place as necessary for record keeping. Additional hurdles in instrumentation involved the maintenance of equipment, which was complicated due to field mice chewing on antenna wiring and other external factors; these maintenance issues complicated data collection and analysis. Management of large data obtained from individual sensors was also problematic. Eventually, it was concluded that the problem could be resolved by setting more appropriate data collection intervals. Despite these challenges with instrumentation, the project team was able to come away with some important lessons learned and generate definitive data through persistence and hard work.<figure id='attachment_8136' style='max-width:558px' class='caption aligncenter'><img class="size-full wp-image-8136" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the Traffic Management Center cabinet repurposed to house instrumentation parts." width="558" height="756" /> Figure 5. Traffic Management Center cabinet repurposed to house instrumentation parts. <figcaption class='caption-text'>Source: MnDOT.</figcaption></figure>Conclusion: The CR-55 Bridge was monitored for three years to evaluate its general performance and the effects of a 5.3 percent grade. Analysis of the three years of instrumentation data indicated the bridge was performing well. The most notable defects included pavement cracking and wall block cracks and chips which are non-structural issues. While the exact nature of these defects remains unknown, future GRS-IBS projects in Minnesota may want to consider using stronger blocks and take a more careful look into design of the interface of the concrete girders and approaches. As for the bridge’s performance in response to the 5.3 percent grade, the bridge abutments have not experienced any significant movements that could be attributed to the presence of the large grade.The CR-55 Bridge project was an example of how GRS-IBS technology is continuing to push its limits. As the bridge with the largest grade, the CR-55 Bridge represented a new application of the technology and the bridge has performed well based on available instrumentation data. Given the project’s success, it is anticipated that more GRS-IBS bridges will be constructed in the state of Minnesota in the near future.Project Contact: Derrick Dasenbrock Geomechanis/LRFD Engineer Minnesota Department of Transportation <a href="mailto:dce@defiance-county.com">derrick.dasenbrock@state.mn.us</a>(651) 366-5597Project Technical Paper: A technical paper has not been published for this project.REFERENCES“Construction Plan for Bridge No. 67564” (construction drawings, Minnesota Department of Transportation, Rock County, 2012).“FHWA EDC Showcase: GRS-IBS Demonstration, Luverne, Minnesota”, YouTube, August 29. 2013. Retrieved from: <a href="https://www.youtube.com/watch?v=QWkREPlQXZ0">https://www.youtube.com/wa…;. Accessed April 12, 2017.“Geosynthetic Reinforced Soil Abutment Bridge”, International Conference on Timber Bridges, Las Vegas, Nevada, 2013.“Rock County Finds Economical Solution with GRS-IBS”, National Concrete Masonry Association, Concrete Masonry Designs, 2016. Retrieved from: <a href="http://cmd.ncma.org/rock-county-finds-economical-solution-with-grs-ibs/…;. Accessed April 18, 2017.Dan Mattison, “Monitoring plan - Rock County GRS-IBS Showcase” (presentation, Minnesota Department of Transportation, 2013).Daniel Alzamora, phone conversation with the author of this document, May 16, 2017Dasenbrock, D.D., Grosser, A., Bryant, G., Swenson, J., and Budge, A., “Performance Study of Minnesota’s First GRS-IBS Structure in Rock County, MN”, The Minnesota Geotechnical Society Annual Conference, February 24, 2017.Derrick Dasenbrock, “Rock County 55 over MN Southern Railway” (presentation, Minnesota Department of Transportation, Rock County Highway Department 2016).Derrick Dasenbrock, phone conversation with the author of this document, June 26, 2017.John Sowada, “GRS-IBS Rock County Bridge 67564” (presentation, Erickson Engineering, 2013).

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Technology

Mechanically Stabilized Earth Wall System