Northeast Boundary Tunnel - Mount Olivet Road Drop Shaft-Video

Video Transcription

Video Summary

Jeremiah Jezerskin presented the construction and design challenges at the Mont Olivet Road site on Washington, D.C.’s Northeast Boundary Tunnel. The site included a 122-foot-deep drop shaft, a ventilation vault, and a deep approach channel, all built in variable Potomac clay and granular soils. The original construction sequence was changed when the tunnel-boring machine arrived earlier than expected, requiring all three excavations to remain open simultaneously.<br /><br />Finite-element modeling assessed whether the unreinforced slurry-wall shaft and permanent structures could withstand the resulting unbalanced loads. Because short-term undrained soil behavior was critical, the team modeled both drained and undrained conditions and evaluated time-dependent soil response. Instrumentation showed strut loads closely matched the model’s predictions, generally within 5%. Monitoring and contingency planning helped manage risks and maintain the schedule. The project demonstrated the value of time-dependent analysis and field monitoring for complex deep excavations.

Keywords

Northeast Boundary Tunnel

Mont Olivet Road

deep excavation

finite-element modeling

undrained soil behavior