Posted on August 11, 2023
Geotechnical engineering services to support the design and construction of the Route 44 over Route 24 interchange in Raynham, MA.
The scope of the design-build procured project included the design and construction of the following elements: full reconstruction with roadway widening, 2-span bridge replacement, two retaining T-walls, four retaining/barrier walls, and several cantilevered overhead guide signs. Nobis coordinated and performed 13 test borings, performed a geotechnical laboratory testing program, and developed the geotechnical recommendations for the bridge foundations, overhead guide cantilever signs, and retaining walls. Geotechnical analyses included bearing resistance, lateral earth pressure, consolidation settlement estimates due to the glaciolacustrine deposit, as well as global slope stability analyses. The analyses were performed in accordance with AASHTO LRFD Bridge Design Specifications and the MassDOT Bridge Design manual. Subgrade preparation observation has been performed during construction to assure that any soft or saturated glaciolacustrine deposits were removed and replaced with compacted structure fill.
challenges
- The portion of the site requiring retaining T-walls was underlain by a glaciolacustrine deposit consisting of silt and clay, which is susceptible to consolidation settlement if additional loads are applied
- The glaciolacustrine deposit has vastly different engineering properties when considering the drained and undrained conditions.
solutions
- Undisturbed soil samples were collected in the test borings, and consolidation and triaxial shear laboratory tests were performed to estimate consolidation behavior as well as the undrained shear value of the glaciolacustrine deposit.
- Advanced 3-D settlement analyses were performed to estimate the long-term settlement due to the roadway widening.
- Detailed settlement monitoring was performed to monitor the settlement of the retaining T-walls during construction, and also to determine if the underlying glaciolacustrine deposit transitioned from an undrained to a drained condition.
results
The results of the settlement monitoring during construction confirmed the estimated settlement obtained in the detailed 3-D settlement analyses during the design phase. These detailed analyses allowed the placement of up to 20 feet of roadway embankment fill over lacustrine deposits without prior ground improvements, thereby reducing the construction cost by over $200,000.
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Posted on May 1, 2018
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.
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Posted on April 27, 2018
Design and construction of a multi-use transit-oriented parking facility
To support the growing need for public transit in Massachusetts, Nobis was selected to provide geotechnical engineering and environmental services for the design and construction of a 540-space mixed use parking garage facility – a priority transit-oriented project for the MBTA’s commuter rail system to expand ridership. The project included a three-story, multi-use addition built directly above the parking structure.
From former light manufacturing and railroad support facility use dating back to the 1800s, the site included legacy underground storage tanks and was impacted by past environmental releases. Massachusetts Department of Environmental Protection classified the property as a past disposal site and had placed deeded use limitations on it.
Nobis provided site design services including site grading and utility layout, storm water management, and streetscape improvements. Landscaping plans were also developed that incorporated native and adaptive plant species and low impact design and maintenance considerations. A geotechnical subsurface exploration program and foundation design support was also performed. Construction phase support including construction documentation, contaminated soil management, soil improvements and dewatering support was also provided.
Challenges
- During the design phase, Nobis discovered underground utilities without sufficient as-built drawings and records indicating their presence and function.
- Located in an urban area, it was spatially difficult during construction to stockpile and properly test contaminated soil.
- Challenging soil and subsurface conditions caused settlement concerns at the locations of proposed retaining nearby to the railway and a pedestrian walkway.
Solutions
- To locate and identify the unknown underground utilities, Nobis conducted extensive CCTV inspection and dye testing and successfully incorporated this new data into the overall site utility design.
- Nobis revised their soil sampling protocols whereby they pre-characterized soils at the excavation locations which allowed for the “live loading” and eliminated the need for on-site stockpiling.
- Nobis developed and put in place several new ground improvement recommendations that successfully address on-site settlement concerns for the new structures.
Results
Nobis completed the design and the garage was successfully constructed. The MBTA continues to promote this project as a model Transit-Oriented Development project, and is currently planning for the development of an apartment complex adjacent to this new commuter rail parking facility.
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Posted on April 30, 2018
Complex geotechnical engineering design to support a 4-mile rail line extension
Over a period of 3 -years, Nobis provided comprehensive geotechnical engineering services for the Massachusetts Bay Transit Authority (MBTA) as part of a $1.1 Billon 4.3-mile Green Line Extension (GLX) light rail project. This project extends the A Green Line from Cambridge, MA to Somerville, MA and included seven new rail stations and a new vehicle maintenance facility. Portions of the GLX are elevated on multiple viaducts comprising 60 total spans, five highway bridges extend over the rail lines, and a railroad bridge crossing over an existing roadway will be replaced. Portions of the rail corridor improvements will be constructed within cut sections requiring 3 miles of soldier piles and cantilevered retaining walls.
Nobis developed and conducted a significant subsurface exploration and drilling program within the active rail corridor and completed a geotechnical laboratory testing program to subsurface materials including stratigraphy, soil and rock strength parameters, settlement characteristics, soil liquefaction potential, and groundwater implications.
Detailed basis-of-design geotechnical analyses were conducted by Nobis for deep foundations including drilled shafts, micro piles, and driven piles, cantilevered and anchored retaining walls systems, ground improvement to stabilize soft soils with aggregate piers, and axial load testing.
Challenges
- The geotechnical subsurface explorations called for advancing 280 test borings to depths of up to 200 feet in an aggressive schedule of only 14 months within an active rail corridor and a dense urban setting. Extensive coordination was required to gain access, avoid impacts to rail operations, and to provide safe working conditions.
- Variable soil conditions and decomposed bedrock formations, high viaduct loads, limited access for large construction equipment, and working within an active rail environment required innovative approach for the viaduct foundation systems.
Solutions
- To successfully complete the test boring program, Nobis assigned a full-time field operation lead and multiple drilling teams to meet the schedule, and proactively coordinated each needed property access and scheduled all railroad protections by the rail operator.
- To address the challenging subsurface conditions, Nobis conducted advanced load modeling, and shear forces and moments on the 120-feet deep viaduct foundations. The team weighed schedule impacts, constructability, and cost implications and ultimately proposed a variety of foundation types – drilled shaft, driven piles, and micro piles to allow train service to remain active during construction.
Results
Project construction is now underway. Once completed, the Green Line Extension is projected to have a total weekday ridership of about 52,000, including 7,000 to 8,000 new riders.
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