Modeling to Monitoring: Evaluating Adjacent Structures Feet from a Boston Excavation-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes geotechnical risk management for a 34-story residential tower built on a 15,500-square-foot site in Boston’s Fenway neighborhood. Excavation for the tower and its two to three levels of underground parking took place beside sensitive structures: a transit tunnel beneath a busy roadway, a historic theater, a three-story brick building, and a narrow public alley.<br /><br />Finite element modeling was used to estimate how excavation and support-of-excavation work could affect neighboring structures. Monitoring tracked movement throughout enabling work, slurry-wall installation, cap-beam construction, and mass excavation. Because adjacent structures had already moved before mass excavation began, the team recognized that less movement remained acceptable during the main excavation.<br /><br />Stakeholders reviewed mitigation options and increased bracing preloads from 30% to 50%, while adopting an observational approach. Other measures considered included adding bracing, using subgrade struts, sequencing slab construction, and accelerating the schedule. Instrumentation provided ongoing performance data, which could be compared with model predictions and used to guide decisions.<br /><br />The presentation’s key lessons are to assess both enabling works and primary excavation support; account for activities that are difficult to model, such as pre-trenching and slurry-wall installation; and treat monitoring as an essential part of risk management. Early, frequent communication and proactive, project-specific support solutions helped the team manage impacts and execute the project successfully.

Keywords

geotechnical risk management

excavation monitoring

finite element modeling

support of excavation

slurry wall installation

bracing preloads

observational approach

adjacent structure impacts

Boston Fenway tower

instrumentation data