Abstract:
Secant Pile Wall Design and Construction for Below Grade Excavation and Construction Adjacent to Operating Rail Line
Marya Gorczyca, P.E., Principal, Haley & Aldrich, Inc.
The Air Rights Parcel 12 project located in the Back Bay neighborhood of Boston involves the construction of a new mixed use development over 6 lanes of Interstate highway and active railroad lines. The Developer of the project added an additional geotechnical challenge which was to construct and underground parking garage less than 10 ft from rail lines on a small parcel further constrained by its small size and proximity of surrounding roads, bridges, and buildings. The railroad Agency dictated extremely restrictive track deflection criteria in order to approve the project and assure no impacts to MBTA commuter rail and Amtrack interstate passenger transportation. This required that the wall be design to unusually small deflection performance criteria to protect the tracks.
This case study will describe the selection, design, and construction of the support of excavation systems required to realize this one specific aspect of a complex Air Rights project. The first Air Rights project to be successfully constructed over Interstate I-90 (Massachusetts Turnpike) in the Back bay in over 40 years.
This case history has an additional component of interest relative to the track monitoring data collected is particularly useful for the design and construction community embarking on similar transit orient development projects. The presentation will present the SOE and track deflection measured during construction and learnings from the automated remote instrumentation and monitoring program. The data will help understand the range of movement that can occur from environmental and other effects in addition to ground movement impacts from the adjacent SOE installation and subsequent excavation.