Abstract:
Construction to replace the Governor Harry W. Nice Memorial/Senator Thomas ‘Mac’ Middleton Bridge began in spring of 2020. As part of a nationwide trend to drive transportation initiatives, the Maryland Transportation Authority (MDTA) partnered with Skanska-Corman-McLean (SCM) Joint Venture to deliver a new US 301 bridge spanning 1.9 miles from Maryland to Virginia over the Potomac River that will improve capacity, safety, and access of the roadway.
After over a decade of planning studies with consideration to project costs, schedule, environmental impact, economic impact, various transportation mode access, existing bridge condition and remaining service life, the new bridge plan settled on a four-lane span with deep foundations that would be constructed less than 200ft north of the existing alignment of the 80+ year old bridge. The project area presented geotechnical design challenges of installing new bridge foundations in problematic soils of the Atlantic Coastal Plain alluvial deposits. With site logistical constraints placing new pile driving operations near existing abutments & piers, a complex instrumentation & monitoring plan was developed in the interest of public safety as the existing bridge remained in service during adjacent construction.
This paper will discuss the geological conditions of the project area, the collaborative approach of various design team members to develop an appropriate monitoring plan utilizing various instrumentation, an understanding of baseline conditional movements of the existing bridge, and impact & response of adjacent construction activity to help deliver effective new bridge foundations while protecting the old ones. The year 2020 and beyond has brought many new challenges to the deep foundation industry. In addition to managing typical geotechnical issues such as embankment surcharge settlement, pile driving vibration impact, lateral ground movements, and scour effect, the geotechnical instrumentation team found new solutions to remote monitoring, network limitations, and supply constraints all while working within a design-build that met the needs of the project team.