Engineering Design Services For the $23M Design/Build Martin’s Point Bridge Replacement

Nobis provided geotechnical services as part of a Design-Build Team for the replacement of the Martin’s Point Bridge in Falmouth-Portland, Maine, a 1,200 foot, 10-span structure with two approach embankments. The proposed alignment ran adjacent to the existing bridge structure which remained in service during construction of the replacement bridge.

Nobis conducted a detailed subsurface exploration program to support the design and construction. The design accounted for seismic parameters in order to evaluate the loose sands and soft clays for liquefaction/cyclic softening potential, and settlement. Nobis’ design included the use of drilled shafts, driven H-Piles, and 24-inch and 30-inch driven pipe piles. Geotechnical support during construction included piezometer and settlement platform analyses, and Pile Driving Analyzer (PDA) testing.

Challenges

  • Site subsurface conditions were complex, and in some locations poor, due to the presence of loose sands over soft, sensitive marine clays extending up to 80 feet below the mudline.
  • The construction of the new bridge adjacent to the existing in-service bridge presented the challenge of sequencing the construction of the piles and embankment in order to limit down drag and lateral spread forces on the proposed piles while minimizing disturbance of the existing piles.

Solutions

  • Nobis developed a 3-dimensional model to evaluate settlement of the proposed north approach embankment over compressible clays and provided the contractor options for mitigating post-construction settlements without adversely impacting the construction schedule.
  • Nobis developed construction staging recommendations with the Contractor related to the pile installation and embankment construction adjacent to the existing bridge.

Results

The bridge was constructed and placed into operation and now provides for the multi-modal needs of the region and is a pedestrian friendly structure with observation decks and pedestrian trails.