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TxDOT US 377 Cresson Relief Route
The US 377 Cresson Relief Route is an alternate route outside Cresson, Texas from about 1.4 miles south to about 1.1 miles north of the SH 171 intersection. HVJ Associates® provided design and construction recommendations for bridges, retaining walls, and embankments. Due to delays in acquiring right-of-entry and a fixed letting date, it was necessary to conduct the geotechnical study on an expedited schedule. Furthermore, we were unable to collect some geotechnical information due to lack of access to a few private properties.
There were several challenges we needed to address through this project. First, right of entry was restricted during the investigation stage, prohibiting the collection of geotechnical borings within portions of the project alignment.
Early on, we identified two core issues that would need to be addressed during the project:
During the investigation, HVJ needed to work around Right-of-Entry challenges to provide geotechnical design information sufficient to obtain a reasonable bid while reducing the risk of change orders to TxDOT.
HVJ then needed to analyze options and recommend the most valuable solution for resolving settlement concerns and addressing the large downdrag .
With little geotechnical information collected for the project, our knowledge of the local geology proved a big help. This knowledge enabled us to collaborate with URS/AECOM and TxDOT Fort Worth District to develop design-bid packages covering several possible scenarios. We made reasonable assumptions that resulted in minimal changes after the contractor was awarded the project. We also mobilized a field team to quickly complete the investigation after right of entry was granted, so that the project was able to stay on schedule.
Another significant challenge was an embankment fill up to 50 feet above the existing ground surface where settlement could impact pavement and retaining wall structures. HVJ determined that the new embankments crossing over 171 and the railroad would result in up to 36 inches of settlement after construction as a result of the onsite soil conditions.
We created a 3-dimensional model of the embankment and calculated the embankment's initial settlement as well as its potential settlement over time to develop several alternative settlement reduction measures.
These possible options we analyzed included:
After evaluation, it was determined the most cost-effective method of installation would be to construct the embankment with select fill and remove and replace the upper 8 feet of existing soil with select fill. We also worked closely with TxDOT to find a nearby source for select fill material that was tested and approved, providing significant cost savings due to proximity.
To address the large downdrag created by the 50-foot-high embankments, we worked with the team’s structural engineers to analyze the magnitude of the downdrag and consider alternative drilled shaft diameters. AECOM and HVJ came up with a solution to increase the shaft diameters and reinforcement of the shafts installed at the existing grade (before embankment construction) down to the tip elevation in the bedrock, while leaving the smaller diameter in the embankment fill where the majority of the downdrag force was being generated. This results in less surface area over the embankment soils but a larger surface area in the bedrock which reduced the downdrag force to a manageable amount.
Krishna Peapully, PE, AECOM
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