Chemicals contributions to Seattle SR99 drive 24 May 2018

Among the many contributors to the success of the 2km long TBM-bored highway tunnel beneath downtown Seattle to replace the city’s State Route 99 Alaska Way Viaduct, BASF made a significant supply of construction chemicals including soil conditioning agents, tailseal grease and concrete additives and repair products. With the materials, the company also supplied support to apply the products and managed the logistics to ensure consistent and reliable deliveries.

Soil conditioning was a significant part of the success of the mega-sized 17.48m diameter EPBM used to excavate the bored tunnel. To provide the best soil conditioner for the project, BASF initiated a university cooperation and research program with the Colorado School of Mines to test chemically enhanced soils to replicate conditions found in the Seattle environment.

BASF products contributed to Seattle’s Big Bertha TBM drive
Photo by Catherine Bassetti Photography

As a result, a new soil conditioner with greater stability, MasterRoc SLF 50, was developed and used on the project. It creates a stable foam with superior half-life qualities to maintain face pressure during excavation operation and at times of planned and unplanned TBM downtime.

With optimum soil conditioning, power consumption is reduced, through a reduction of torque; soil extraction is optimized; and cutterhead wear is decreased.

Also used on the SR99 project in Seattle, BASF supplied, among other products, annulus grout admixtures which provided retarders to affect the setting time of the grout.

It supplied also polymer injection systems to prevent water ingress into the tunnel at the portal, and precast concrete segments admixtures to ensure durability and efficient production of the precast concrete segments.

“We are very pleased to have been part of one of the world’s largest diameter TBM tunnel projects,” said Jim Lindsay, Regional Business Segment Manager, BASF Construction Chemicals North America.