Project Type: Foundation, Evaluation, and Design.
Industrial Office Building Foundation Stabilization
Issue
Vital Structures was retained for design of stabilization repairs as a result of foundation cracks, displacement, and deterioration at a Fitchburg MA office building. Upon removal of interior wall finishes, the owner observed horizontal cracking in a reinforced concrete basement foundation wall and a failing concrete masonry pilaster, which prompted a comprehensive engineering evaluation.
Diagnosis
Vital Structures performed an evaluation using destructive test cuts of the CMU pilaster, ground penetrating radar (GPR) location of foundation wall steel reinforcing, placement of crack monitors, and a Geotechnical investigation with soil borings. The evaluation concluded the following:
- The CMU pilaster had been constructed using 4” and 12” hollow block to achieve a 16” square profile. Due to the narrow profile of the 4” blocks, combined with moisture infiltration, the 4” projection of the pilaster had failed and ‘lopped’ off of the wall.
- Horizontal cracks in the foundation wall were noted to correspond directly with the greatest backfill height along the basement wall. Further, the groundwater table was found to be 4’-0” ± below the basement slab, and periodic vehicular surcharge (parking) is present at the exterior of the building in this area. An analysis of the foundation wall found that the wall was overstressed, confirming the horizontal cracks were related to flexural stress.
Our Solution
Vital Structures prepared design documents, solicited bids and performed construction administration services for the foundation repair project, including the following scope:
- Placement of three (3) 12’-0” tall reinforced concrete buttress walls to aid with earth retaining forces in the foundation wall.
- Replacement of the CMU pilaster with reinforced concrete pilaster, including temporary shoring to relieve first floor loads.
- Self-consolidating concrete was used to replace the pilaster due to access constraints. Exterior shells of the masonry were able to be kept intact to avoid excavation and further exterior repairs.
- Exterior masonry repairs were performed to limit moisture infiltration and deterioration of the CMU walls, including re-pointing, sealants, and targeted masonry coatings.
