Abstract:
Cohesionless fill and granular soils encountered at the Lindbergh Parking Expansion, Northwest Drive Grade Separation project for the Minneapolis-St. Paul International Airport required soil stabilization for the construction of a new 19-foot tall retaining wall. If untreated, excavation through the surficial soils, to construct the wall, would result in instability and settlement of the existing traveled roadway. The stabilization program was required to increase the strength and stability of the in-situ soils and fill, and to provide temporary support to existing structures and utilities. The project specifications initially allowed two stabilization options: chemical permeation grouting with sodium silicate and jet grouting. The area requiring stabilization was approximately 200 feet long and 15 to 25 feet wide, with treatment depths ranging from 8 to 12 feet. Considering the large area of work, many sleeve port grout pipes would be required to adequately perform the chemical grouting, and the shallow depth could inhibit the effectiveness of jet grouting. As a more efficient and cost-effective alternative, Keller proposed utilizing shallow, mechanically mixed soil stabilization. This paper will describe the design approach, technical considerations, and successful execution of the work.