Interstate 84 Echo Bridge Utah

<figure id='attachment_8160' style='max-width:931px' class='caption aligncenter'><img class="size-full wp-image-8160" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Two photographs (a) Completed and (b) old westbound Echo bridges." width="931" height="668" /><figcaption class='caption-text'> Figure 1. (a) Completed and (b) old westbound Echo bridges. Source: Google Maps</figcaption></figure>Location: Summit County, Utah Owner: Utah Department of Transportation Year Constructed: 2013 National Bridge Inventory (NBI) Number: F-851 Crossing Type: Roadway bridge over road Superstructure Type: Adjacent Precast Concrete Boxes Span: 57.7 feet Maximum Wall Height: 19.2 feet Maximum Wall Face Width (edge to edge): 149 feet for all abutments Skew: 0 degrees Facing Type: Segmental Retaining Wall (SRW) Average Daily Traffic (ADT) (when constructed): 8,300 Contract Type: Design-Bid-Build Unique Project Feature: The first GRS-IBS designed for high ADT and high volume of truck traffic (40% of vehicles). The first GRS-IBS to be constructed with lateral bridge slide as accelerated bridge construction (ABC) method.Background: The Interstate 84 (I-84) eastbound (EB) and westbound (WB) bridges over Echo Frontage Road are located approximately 50 miles east of Salt Lake City near the town of Echo in Summit County, Utah. Originally constructed in 1971, the twin EB and WB bridges had a three-span superstructure composed of a cast-in-place (CIP) reinforced concrete solid slab superstructure, bents, and concrete abutments supported by steel piles (see figure 1b). Given their age and the fact that neither bridge provided the desired 15-foot clearance, the twin bridges were deemed functionally obsolete, structurally deficient, and were scheduled for replacement in 2013.<figure id='attachment_8161' style='max-width:1146px' class='caption aligncenter'><img class="size-full wp-image-8161" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Sketches of the project location. To the left, location of Summit County, Utah to the right, location of the I-84 Echo Bridges." width="1146" height="578" /><figcaption class='caption-text'> Figure 2. (a) Location of Summit County, Utah and (b) I-84 Echo Bridges. Source: Open Street Map, ESRI, FHWA</figcaption></figure>The portion of I-84 located in Echo is frequently used by motorists traveling to and from Salt Lake City and visiting Echo. While Echo is not a highly populated town, it attracts many tourists from across the state due to its rich history with the Union Pacific Railroad and as a stopover on the Mormon Trail. Other motorists on the interstate include those traveling to the Echo Reservoir, a popular recreation spot during the summer months, and truck drivers. The Utah Department of Transportation (UDOT) oversaw the project and made strong efforts to minimize traffic disruptions by informing highway users of construction-related delays and closures in advance. Minimizing traffic disruptions along I-84 was especially important for truck drivers, who would suffer most if not warned about closures in advance.Deployment: UDOT is known for its efforts to minimize traffic disruption during construction. Often, UDOT will take specific steps to reduce the number and duration of road closures. Projects led by UDOT regularly feature financial incentives for early project completion and the latest technology to minimize construction duration. Apart from minimizing inconvenience for motorists, shorter construction times also reduce safety risks for workers.Reducing construction time and minimizing inconvenience to motorists was especially important during replacement of the I-84 Echo bridges. The I-84 Echo bridges had an average daily traffic (ADT) of 8,300 vehicles per day, with 40 percent of total traffic resulting from trucks. Any road closures would impact a large number of users and have a significant effect on traffic flow. Given these concerns, the Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) method was selected to replace the EB and WB bridges.Using GRS-IBS allowed UDOT to reduce construction time and costs. Rapid construction is a feature of GRS-IBS made possible because the method minimizes the use of CIP concrete that requires lengthy curing time. Additionally, construction of GRS-IBS bridges is a simple process that does not require special equipment or workforce needs; this further reduces construction time. GRS-IBS also uses simple materials that can be procured locally. Given Echo’s rural location, the ability to use local materials has been especially helpful to UDOT in reducing costs. Procuring special materials, as would be needed if another method was used, would require travel to Salt Lake City and drive up project costs. Site conditions were also favorable for GRS-IBS technology. The EB and WB bridge footprints were not underlain by the liquefiable soils that are fairly common in other parts of Utah. Instead, as is preferred for GRS-IBS, the bearing soils were composed of layers of gravel, clayey sand, lean clay, and silty clayey sand that had largely low compressibility.<figure id='attachment_8162' style='max-width:845px' class='caption aligncenter'><img class="size-full wp-image-8162" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the construction of the median bridge." width="845" height="508" /><figcaption class='caption-text'> Figure 3. Construction of the median bridge. Source: Utah Department of Transportation.</figcaption></figure>During the construction process, many measures were adopted to further reduce construction time and project costs. GRS-IBS bridge superstructures were constructed using prefabricated bridge elements and systems (PBES) in the form of adjacent precast concrete boxes and this accelerated construction even more. To reduce construction time even further, an accelerated bridge construction (ABC) method, lateral bridge slide, was employed. The bridge slide method involved construction of a median bridge between the EB and WB bridges that did not disrupt traffic (see figure 3). The median bridge featured a slide-capable superstructure that would eventually replace the superstructure of the existing EB bridge. Traffic was diverted from the WB bridge to the median bridge, and the WB bridge was demolished and replaced with the GRS-IBS bridge in-place; the WB bridge did not require a superstructure slide. After this step was complete, traffic from the median bridge was shifted back to WB bridge and traffic from the EB bridge was diverted to the median bridge. The existing EB bridge was then demolished and GRS abutments were constructed. Once GRS abutments at the EB bridge were complete, the median bridge was shut down and its superstructure was slid to the EB bridge. In total, it took the contractor 27 hours to slide the superstructure and complete the system at the EB bridge. Afterward, all traffic at the EB and WB bridges resumed and the contractor collected a $20,000 incentive from UDOT for minimizing road closure time. Videos of project construction time-lapse, including the bridge slide, can be found in the references section.Project Challenges and Solutions: Most of the challenges described in this section relate to using the bridge slide method and the general time constraints UDOT imposed on the project. The solutions to these challenges, presented below, were effective and resulted in successful completion of the project.Construction staging and bridge slide While the construction staging used for the I-84 Echo bridges minimized road closures, planning required significant foresight. For example, the median bridge had to be completed first and needed to temporarily accommodate traffic. The median bridge then had to be moved in place of the EB bridge in the most efficient manner. In order to complete this task efficiently, approaches for the median and EB bridges were constructed using reinforced soil layers with a one-foot wide trench between the reinforced soil layers and superstructure. The trench had to be at least one-foot wide to allow for the compaction equipment access and extended to the depth of the concrete footing. The trench was filled with compacted gravel encased with geotextile to prevent migration of fines into the gap, before being paved over to accept traffic. Constructing approaches this way provided a quick and clean “release” of the slide-capable superstructure. The gravel used to fill the trench was vacuum excavated prior to the superstructure move and then placed in the same gaps at the EB structure prior to pavement placement. As a whole, the process was successful and difficulties were only encountered with the vacuum excavation of the gravel. Vacuum excavation of the gravel, about one inch in diameter, was slightly challenging because the vacuum truck had difficulty pulling in the material. To avoid this, a lighter, smaller diameter, gravel could have been used to make the vacuum excavation easier and more efficient. In general, this approach construction method was conducive to the bridge slide and GRS-IBS combination.Bridge slide’s low settlement tolerance The bridge slide method has a very low tolerance for differential settlement. The soils under the I-84 Echo bridge GRS abutments were composed of mostly dense sandy gravel underlain by a stiff clay layer; this clay layer was thicker at the EB site. Because of the presence of additional compressible soils at the EB site, a fill surcharge was placed where appropriate to minimize the risk of differential settlement during the bridge slide (see figure 4). The surcharge preloaded and compressed the thicker clay layer within the EB site and ensured success of the bridge slide.<figure id='attachment_8163' style='max-width:692px' class='caption aligncenter'><img class="size-full wp-image-8163" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the Surcharge placed at eastbound bridge site." width="692" height="589" /><figcaption class='caption-text'> Figure 4. Surcharge placed at eastbound bridge site. Source: Utah Department of Transportation.</figcaption></figure>Minimizing the construction time using five-ton rollers At each bridge, both abutments were built simultaneously. The use of five-ton rollers, shown in figures 5a and 5b, instead of small plate compactors helped make the project more efficient. The reinforced layers at each bridge were compacted using two rollers on each side, which reduced construction time even further.<figure id='attachment_8164' style='max-width:1182px' class='caption aligncenter'><img class="size-full wp-image-8164" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Two photographs. To the left, Five-ton roller on top of finished GRS layer, to the right, on top of a roadway." width="1182" height="385" /><figcaption class='caption-text'> Figure 5. (a) Five-ton roller on top of finished GRS layer and (b) on top of a roadway. Source: Utah Department of Transportation.</figcaption></figure>Conclusion: The I-84 Echo Bridge Project was the first to combine GRS-IBS method with lateral bridge slide. The project bridges were also the first GRS-IBS bridges to serve an interstate, the first GRS-IBS bridges to serve a high ADT, and the first to serve a high volume of truck traffic. To evaluate performance, the bridges were instrumented with inclinometers that showed no significant deflections within the abutments as of the time of this writing.The project is a great illustration of GRS-IBS’s potential for serving interstates and other roads with high ADT. GRS-IBS technology started out as an option for low ADT, county roads and is transforming into a method that can be applied to various conditions, including high ADT and high truck volume roads. While it was the first, the I-84 Echo bridges are not the only GRS-IBS bridges serving a high ADT highway. Between 2013 and 2015, a total of 20 bridges were constructed with ADTs of 2,000 to 34,000, including other bridges on the National Highway system, interstates, and ramps on and off interstate highways. These projects are a testament to the success of GRS-IBS technology and have inspired some states, such as Pennsylvania, that previously only used GRS-IBS for low ADT roads to explore the possibility of expanding this method to higher ADT roads.Project Contact: Jim Higbee Geotechnical Engineer Utah Department of Transportation <a href="mailto:dce@defiance-county.com">jhigbee@utah.gov</a>(801) 230-9280Project Technical Paper: A technical paper has not been published for this project.REFERENCES“Echo Frontage Road, Bridge Replacement D-783” (construction drawings, Utah Department of Transportation, Structures Division, 2012).“Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS)”, YouTube, 2015. Retrieved from: <a href="https://www.youtube.com/watch?v=1NOLcVtAln0">https://www.youtube.com/wa…; (1:24:44). Accessed April 24, 2017.“I-84 Echo Bridge GRS-IBS Construction Time-lapse”, YouTube 2013. Retrieved from: <a href="https://www.youtube.com/watch?v=g2o1fN2-qzA">https://www.youtube.com/wa…;. Accessed April 12, 2017.“I-84 Echo Bridge Move and Geosynthetic Reinforced Soil”, YouTube 2013. Retrieved from: <a href="https://www.youtube.com/watch?v=atGicyyj6D8">https://www.youtube.com/wa…;. Accessed April 21, 2017.“Utah Demonstration Project: Geosynthetic Reinforced Soil Integrated Bridge System on I-84 near Salt Lake City” (DRAFT REPORT, U.S. Department of Transportation. Federal Highway Administration, 2014). Retrieved from: <a href="https://www.fhwa.dot.gov/hfl/projects/ut_grs-ibs_i84_saltlakecity.pdf">…;. Accessed April 21, 2017.Bryce Wadsworth, “I-84 - Echo Frontage Road, Bridge Replacement Project - Contractor Perspective” (presentation, Utah Department of Transportation, 2013).Daniel Alzamora, phone conversation with the author of this document, May 16, 2017Donath Picardo, “I-84 - Echo Frontage Road, Bridge Replacement Project - Design Perspective” (presentation, Utah Department of Transportation, 2013).Higbee, J., Klophaus, J. and Swandwick, C., “Interstate Accelerated Bridge Replacement in Utah; Minimizing User Impacts By Optimizing Construction Sequence And Methods” Proceedings: 2014 National Accelerated Bridge Construction Conference. Miami, Florida. p. 45-50. Retrieved from: <a href="https://abc-utc.fiu.edu/wp-content/uploads/sites/52/2016/01/Proceedings…;. Accessed April 12, 2017.Jason Klophaus, “I-84 - Echo Frontage Road, Bridge Replacement Project - Contractor Perspective – Slide Design” (presentation, Utah Department of Transportation, 2013).Jim Higbee, “I-84 - Echo Frontage Road, Bridge Replacement Project. Design Perspective – GRS-IBS” (presentation, Utah Department of Transportation, 2013).Jim Higbee, phone conversation with the author of this document, June 7, 2017.

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Technology

Mechanically Stabilized Earth Wall System