BR 1-366 on Chesapeake City Road Delaware

<figure id='attachment_8103' style='max-width:1374px' class='caption aligncenter'><img class="wp-image-8103 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="A photograph of the Completed BR 1-366 on Chesapeake City Road" width="1374" height="1003" /><figcaption class='caption-text'> Figure 1. Completed BR 1-366 on Chesapeake City Road.</figcaption></figure>Location: New Castle County, Delaware Owner: Delaware Department of Transportation (DelDOT) Year Constructed: 2013 National Bridge Inventory (NBI) Numbers: 1-366 Crossing Type: Roadway bridge over stream Superstructure Type: Adjacent Precast Concrete Boxes Span: 28 feet Maximum Wall Height: 20 feet Maximum Wall Face Width (edge to edge): 48 feet Skew: 0 degrees Facing Type: Concrete Masonry Unit (CMU) Average Daily Traffic (ADT) (when constructed): 2023 Contract Type: Design-Bid-Build Unique Project Feature: The most heavily instrumented GRS-IBS bridge; first GRS-IBS bridge in DelawareBackground: Bridge 1-366 (BR 1-366) is located in New Castle County, Delaware just north of the Chesapeake and Delaware (C&D) Canal that connects the Chesapeake and Delaware Bays. BR 1-366 is located on Chesapeake City Road, parallel to the C&D Canal, near the border of Delaware and Maryland (see figures 2a and 2b). New Castle County is the northernmost of Delaware’s three counties. While New Castle is the smallest county in Delaware, it has the highest population density and is the most economically developed. Chesapeake City Road, located in the central portion of the county, is classified as a major collector road and represents an important east-west connection; the road had an average daily traffic (ADT) of 2,023 in 2013.<figure id='attachment_8102' style='max-width:999px' class='caption aligncenter'><img class="wp-image-8102 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Sketches of the project location. To the left, location of New Castle County, Delaware, to the right, location of BR 1-366." width="999" height="505" /><figcaption class='caption-text'> Figure 2. (a) Location of New Castle County, Delaware and (b) BR 1-366. Source: Open Street Map, ESRI, FHWA.</figcaption></figure>Constructed in 1935, BR 1-366 was rapidly reaching the end of its design life when replacement was first proposed. The original bridge, with a 29-foot span and concrete encased steel beams on masonry abutments, was structurally deficient, functionally obsolete, and needed to be replaced. Given its location along Chesapeake City Road, BR 1-366 provided an important connection for motorists passing through and from the surrounding communities. Few alternatives to Chesapeake City Road were available; a local detour would take a motorist three miles out of the way, while a regional detour would be 17 miles long and go through Maryland. The lack of efficient detours and higher ADT meant that the bridge owner, Delaware Department of Transportation (DelDOT), could not shut down BR 1-366 for long. To construct the replacement bridge quickly and minimize inconvenience for motorists, DelDOT decided to use Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS). The University of Delaware (UD) motivated DelDOT to use the GRS-IBS technology and was heavily involved in the design process. The project team also benefited from technical guidance provided by Federal Highway Administration (FHWA) that promotes the use of GRS-IBS.Deployment: The new BR 1-366 had a similar footprint to the original structure. The maximum height of the GRS abutments was 20 feet and the width was 48 feet. The GRS walls were constructed using concrete masonry units (CMU). The superstructure, composed of adjacent precast concrete beams with a span of 28 feet and width of 40 feet, accommodates two lanes and two shoulders. The bridge construction utilized local materials as GRS-IBS uses simple materials that are often readily available.Since BR 1-366 was the first GRS-IBS bridge in the state of Delaware, it was decided to instrument the bridge. Instrumentation efforts were partially funded through FHWA’s Innovative Bridge Research and Deployment (IBRD) Program. The extensive bridge monitoring program involved the following instruments: <ul> <li style="list-style-type: none;"><ul> <li>Inclinometer Sensors were installed to monitor displacements in the clay layer below the bridge’s reinforced soil foundation (RSF).</li> <li>Piezometers monitored water pressure in the clay layer below the bridge’s RSF.</li> <li>Pressure cells were installed under the foundation, within the abutments and between the road approach and superstructure, to measure static and instantaneous pressures induced by live loads on the road.</li> <li>Strain gauges were installed in abutments to monitor strain within the geotextiles.</li> <li>Thermistors were installed in abutments to monitor temperature and its effect on measured strains in the geotextile.</li> <li>Volumetric moisture sensors were installed in the abutments to monitor soil moisture content and its effect on strains in the geotextile.</li> <li>Surveying points were installed on the facing of the abutments, as shown in figure 3, to monitor wall deflections during the operation of the bridge.</li></ul></li></ul><figure id='attachment_8104' style='max-width:1425px' class='caption aligncenter'><img class="size-full wp-image-8104" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="Photograph of the surveying points installed on GRS wall facing." width="1425" height="1067" /><figcaption class='caption-text'> Figure 3. Surveying points installed on GRS wall facing.</figcaption></figure>Project Challenges and Solutions: BR 1-366 faced minor challenges during construction and instrumentation because GRS-IBS was a new technology in the state and the bridge was heavily instrumented GRS-IBS bridge. Other challenges did occur, but they were more general in nature. Some of these challenges and solutions are described below.Compressible soils Based on subsurface investigations conducted for the project, it was concluded that the proposed bridge foundations were underlain by stiff clays and medium to dense sands. The impact of this compressible material within the project site had to be carefully evaluated to avoid extensive settlements and stability issues. While the dimensions of the new GRS-IBS structure were fairly similar to the old bridge and the abutments already had preloaded the soils below the proposed RSF, more studies had to be conducted. External and internal stability analyses were performed following the methodology outlined in FHWA’s Geosynthetic Reinforced Soil Integrated Bridge System Interim Implementation Guide (2011). The results of the analyses helped finalized the geometry of the bridge and ensure that the structure was stable.The use of No. 8 stone The project team considered using AASHTO M-43 No. 8 stone as backfill because it was readily available. This stone had not been previously used by DelDOT as backfill and had to be further studied. Aside from being readily available, the No. 8 stone was thought to be beneficial for GRS abutments located near streams; the stone is comprised of fairly uniform and coarse material that provides free drainage during storm events and any subsequent rises in stream water levels. The feasibility of using No. 8 stone for BR 1-366 was determined by conducting grain size distribution tests in the UD lab and ensuring the results agreed with DelDOT standards. FHWA guidance recommends the use of an open graded aggregate such as a No. 8 stone as backfill at water crossings to minimize issues associated with hydrostatic forces, piping of materials, and variability in fill strength. For the purposes of reducing costs and increasing speed of construction, it is important to specify a gradation that is locally available and that closely resembles the requirements in FHWA guidance.Instrumentation-related issues BR 1-366 was the most heavily instrumented GRS-IBS project. The instrumentation was designed by UD and they also collected and analyzed data. During instrumentation installation, maintenance, and data processing, the project team encountered several challenges. One of the challenges involved inclinometer sensor installation. Sensors had to be installed in the stiff clay layer, below the proposed RSF, and the abutments from the old bridge were in the way of installation. To reduce construction time, it was decided to install the inclinometers by drilling through the old abutments instead of waiting for their removal. Using this process allowed construction to proceed without being disrupted by the inclinometer installation. Other means of reducing construction time while installing instrumentation involved installation of the strain gauges within the abutments. The strain gauges were attached to the geotextiles in the UD lab before construction and this procedure significantly minimized any construction delays in the field resulting from instrumentation installation.Conclusion: Despite the challenges with instrumentation, replacement of BR 1-366 was a success. As of this writing, BR 1-366’s performance has been excellent and UD continues to monitor the bridge to quantify its long-term performance. For example, the measured horizontal deflections were generally between two and ten millimeters and measured settlements were ranging from none to five millimeters over time. None of the measurements ever exceeded 10 millimeters. These reading fluctuations were thought to be a result of the six-millimeter precision of the surveying operation. Given this information and the recorded measurements, it can be concluded that the settlements and horizontal deflections of the bridge are minor.Whereas the bridge features the most extensive instrumentation program, it is not the only GRS-IBS bridge that has been instrumented. Select GRS-IBS bridges in the states of Louisiana, New York, Utah, Massachusetts, and others have featured some form of instrumentation. Given their positive experience with BR 1-366, DelDOT successfully delivered another GRS-IBS project in 2014.Project Contact: Chris Meehan Associate Professor Department of Civil and Environmental Engineering University of Delaware <a href="mailto:cmeehan@udel.edu">cmeehan@udel.edu</a>(302) 831-6074Project Technical Paper: A technical paper has not been published for this project.REFERENCESChesapeake and Delaware Canal – Web Page. Retrieved from <a href="http://www.pennways.com/%20CD_Canal.html">http://www.pennways.com/ CD_Canal.html</a>. Accessed June 27, 2017.Chris Meehan, phone conversation with the author of this document, June 28, 2017.Daniel Alzamora, phone conversation with the author of this document, May 16, 2017.New Castle County, Delaware- Web Page. Retrieved form <a href="http://www.nccde.org/">http://www.nccde.org/</a>. Accessed June 27, 2017.Nicks, J., Meehan, C., Dasenbrock, D., Conors P., and Alzamora, D. “Performance of Geosynthetic Reinforced Soil Integrated Bridge System (GRS IBS)” (presentation, Transportation Research Board (TRB) Webinar, 2016).Percival McNeil, “BR 1-366 on Chesapeake City Road - GRS Abutment Showcase” (presentation, DelDOT Bridge Design, Delaware Department of Transportation, 2013).Talebi M., “Analysis of the field behavior of a Geosynthetic Reinforced Soil Integrated Bridge System during construction and operation”. Dissertation, University of Delaware, 2016.Talebi, M., Meehan, C. L., Becker, M. L., and Cacciola, D. V., “Design of a GRS-IBS Bridge. Bridge 1-366, Chesapeake City Road” (presentation, Innovative Bridge Research and Deployment Program, University of Delaware, 2013).Talebi, M., Meehan, C. L., Cacciola, D. V., and Becker, M. L., “Rapid Replacement”, American Society of Civil Engineers, April 2014.Talebi, M., Meehan, M. L., Cacciola, D. V., and C. L., Becker, “Design and Construction of a Geosynthetic Reinforced Soil Integrated Bridge System”, GeoCongress, 2014.

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Technology

Mechanically Stabilized Earth Wall System