The paper presented reviews the construction of a new commercial office complex on the Seattle waterfront that required an innovative approach to the below grade shoring and waterproofing. The site is adjacent to existing historic unreinforced masonry buildings. The foundation extends over 40 feet below the water table. The excavation employed Continuous Soil Mix (CSM) construction to address subsurface obstructions and provide a more watertight shoring system to minimize the de-watering efforts.
CSM technology utilizes a set of cutters to break down and mix the native soils with a cement grout to create a soil-cement mixture with a high compressive strength. This paper provides an overview of the CSM technology, the excavation and de-watering process, and the placement of soil tie-back anchors.
To waterproof the mat slab and foundation walls, a below-grade bentonite waterproofing system was used. This paper outlines the preparation of the CSM shoring wall, the use of a rat slab to provide a surface to receive the bentonite membrane, the waterproofing of the mat slab tie penetrations and the waterproofing of wall tie-backs and pipe penetrations.