Abstract:
GZA provided geotechnical engineering services from conceptual design through final design and construction of the Madawaska International Bridge replacement, serving as a subconsultant to the bridge designer, HNTB Corporation for the Maine Department of Transportation. The new bridge consists of an 1,850-foot long, six-span, steel girder, concrete deck bridge crossing the St. John River from Madawaska, Maine to Edmundston, New Brunswick.Â
The River is too shallow for access by any typical test boring equipment. GZA’s test boring subcontractor constructed a special drilling platform, and the drill platform and drill rig were positioned on each borehole location using a helicopter.
Spread footings bearing on bedrock and drilled shafts were considered for river piers, and designs were provided for both alternatives. The contractors selected and bid the drilled shaft alternative, likely due to anticipated challenges and resulting cost for cofferdams extending to bedrock that would be difficult to quantify.
Each pier was supported by four, 6-foot-diameter drilled shafts with 5.5-foot-diameter, 15-foot-long rock sockets. GZA developed rock engineering properties for use in conducting compressive and tensile axial resistance analyses. Â GZA developed soil and bedrock models for lateral shaft analyses to evaluate rock socket depth and development of stiffness matrices for representative piers for use in the designers bridge model.
GZA provided construction quality assurance and control services, including confirmation test borings at every other shaft to provide a minimum 2 total borings per pier to evaluate bedrock elevations and inclination for each shaft, logging of drilling activities, assessment of socket cleanliness through the Shaft Quantitative Inspection Device (SQUID), monitoring of concrete placement, and utilization of thermal integrity profiling (TIP) testing for assessing the drilled shaft quality. GZA’s extensive experience in design, meticulous construction observation, and precise interpretation of test results pertaining to deep foundations played a pivotal role in ensuring the project’s progress.