Monitoring the performance of earth pressure balance tunneling in Toronto

摘要

Tunneling for a new subway in Toronto was monitored to assess construction performance. Ground conditions included over-consolidated lacustrine silt, sand, and clay deposits below groundwater levels and hard glacial till interspersed with boulders. Two earth pressure balance tunnel boring machines (TBMs) were used for mining. Control of ground movements and their subsequent effect on nearby facilities depended on appropriate machine operation. The TBMs included automated data acquisition systems to monitor operating parameters. Additional data was manually recorded. Precise leveling of over 1,200 settlement points was carried out during tunneling. Data from the TBMs and instruments were simultaneously transmitted to the engineer and contractor. Semi-automated database systems were used by the site staff to plot and interpret the data on a continuous basis. This paper presents example results of the monitoring program with emphasis on the program design and purpose, organization of responsibilities, data management, and lessons learned related to the performance of this tunneling project.