Excavation Structural Support
Scarborough, ME: In Situ Soil Mixing, Lowes - Retaining Wall Sub-grade Improvement
Geo-Solutions Inc. installed soil-cement columns using in situ shallow soil mixing. The purpose of the soil mix columns was to improve the shear strength of the soil under a future retaining wall. The project was part of the construction of a new Super Wal-Mart.
Geo-Solutions offered a value engineering solution on this project. The design originally called for 24-inch diameter stone columns to be installed. Geo-Solutions' proposed alternate for 36-inch soil-cement columns was accepted by the engineer. A pattern of 3 rows of columns, spaced 8 feet apart, was selected. A total of 246 columns were installed to an average of 30 feet deep. The columns were drilled through sand and clay layers to bear on the glacial till layer.
Minimum unconfined compressive strength of 60 psi was specified by the engineer. Geo-Solutions achieved a range of 96 to 278 psi in samples collected during production, with an average of 194 psi.
The significant challenges on the project were:
- Meeting the schedule of the General Contractor and coordinating field operations with the other subcontractors. Geo-Solutions was able to accelerate the installation of the soil-mix columns.
- Working from an earthen "leveling pad" that was below the level of the water table and thus saturated. Geo-Solutions' drill rig worked on timber crane mats for the duration of the project.