Innovative SOE Solutions for Shaft Construction: Getting to Depth with Diaphragm Walls at Westerly Storage Tunnel-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes the use of diaphragm walls as an innovative support-of-excavation solution for shafts in Cleveland’s Project Clean Lake, a 25-year, $3 billion program to reduce combined sewer overflows into Lake Erie from 4.5 billion to 0.5 billion gallons annually.

The original shaft designs relied on secant piles and, at some locations, rib-and-liner plates and conventional rock support. The accepted value-engineering alternative used diaphragm walls keyed into Chagrin Shale bedrock:

- <strong>WST-3:</strong> 50-foot-diameter shaft with 152-foot-deep walls.
- <strong>WST-1:</strong> 53-foot-diameter shaft with 97-foot-deep walls.
- <strong>WST-2:</strong> 21-foot-diameter shaft with 172-foot-deep walls.

Walls were excavated through clay and shale using mechanical clamshells and, at WST-2, a Hydrofraise. Bentonite or cement-bentonite slurry supported excavation. The shaft walls were unreinforced, relying on compression-ring action; WST-3’s gate structure used steel-beam reinforcement.

Construction required careful planning around a century-old sewer, an adjacent school site, limited work areas, winter conditions, and the geometry and sequencing challenges of small-diameter shafts. Teams used verticality sensors and surveys to control installation and developed joint and connection-panel details for site-specific constraints.

The diaphragm-wall approach created structural cutoff walls socketed into bedrock. It eliminated the need for deep depressurization wells and rib-and-liner plates, reduced the number of subcontractors, improved safety, and helped shorten the schedule and lower costs.

Keywords

diaphragm walls

shaft excavation

Project Clean Lake

Cleveland sewer overflow

Chagrin Shale

bentonite slurry

Hydrofraise

compression-ring action

value engineering

bedrock socketed cutoff walls