- Geotechnical Design
- Subsurface Investigation
- 3D Modeling
- Stability Evaluations
- Support Services
Nobis is providing geotechnical services as part of a Design-Build Team for the replacement of the Martin’s Point Bridge in Falmouth-Portland, Maine. The proposed bridge will be approximately 1,200 feet long consisting of 10 spans, with two approach embankments approximately 25 to 30 feet high. The proposed alignment is will run along the existing bridge which is to remain in service during construction of the proposed replacement bridge.
Nobis has completed preliminary geotechnical design and is currently providing design and construction services. The site contains numerous geotechnical challenges due to the presence of loose sands over soft sensitive marine clays extending up to 80 feet below the mudline. The construction of the proposed bridge adjacent to the existing in-service bridge presents the challenge of sequencing the construction of the piles and embankment in order to limit downdrag and lateral spread forces on the proposed piles while minimizing disturbance of the existing timber piles.
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 is working closely with the Design Team and Contractor in order to provide construction staging recommendations related to the pile installation and embankment construction adjacent to the existing bridge.
Nobis determined the design earthquake and appropriate seismic parameters in order to evaluate the loose sands and soft clays for liquefaction/cyclic softening potential and to estimate seismic settlement of deep marine sands using standard penetration test and cone penetration test data. Nobis evaluated slope stability of the proposed embankments under undrained and long-term drained conditions and with the addition of a seismic load.
Geotechnical support services will be provided during construction, such as reviewing piezometer and settlement platform results, in order to confirm assumptions used during design. Nobis will also be on-site during pile installation and will review Pile Driving Analyzer (PDA) testing.