Mission Critical Application
Prior to the launch of Bertha — Seattle’s EPB TBM — in July 2013, the project teams managing the largest diameter TBM scheduled to excavate the Alaskan Way viaduct replacement tunnel, needed a prevention solution.
As a precaution, to ensure the safety of project personnel and the project itself, the need for a potential hyperbaric intervention was genuine. Hydrated bentonite would be used to seal the massive excavation chamber if intervention was required.
A fully automated bentonite plant, engineered to produce 180m3/hr. of bentonite slurry, with two independent 150m3 hydration holding tanks, readied to transfer via a 8″ pipeline by progressing cavity pump to the TBM’s holding tank, was built for the job.
Hydrated betonite is jointly used in the preparation of the “A” component grout commonly used in tunneling projects. The use of properly mixed, stored, and pumped hydrated bentonite significantly reduces bi-component grout bleed.