Ground, building and utility deformation monitoring is a well-accepted and required practice for underground construction works in urban environments. The availability of real-time monitoring data during construction allows stakeholders to stay ahead of potential problems, to make decisions prior to damage occurrence, and ultimately to reduce damage and cost risk. This paper presents the analysis of a comprehensive monitoring program carried out during the East Side Access Queens bored tunnels project in New York City. The project involved the construction of four near surface, closely spaced metro transit tunnels beneath the rail yards and mainline railroad tracks. The close proximity of the tunnels provides a unique opportunity to examine the influence of multiple closely spaced tunnel openings on ground deformation, particularly the accumulation of vertical surface deflection due to consecutive tunnels. The project also allows for a direct comparison between deformation monitoring techniques as both manual survey based monitoring and automated total station monitoring were used on the project. This paper will provide an overview of the monitoring program as a component of the risk management process on the project. The monitoring program will be described in detail and results will be presented. The paper also addresses potential improvements to risk-reduction through monitoring.
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