PolyLevel Deep Foam Injection to Stabilize and Lift Warehouse Floor

Tuesday, February 11th, 2025 by Abbey George

Challenge

The ECU Worldwide Warehouse, located in Miami Florida, is an approximate 165,000 square foot structure built in 1955. The east side of the warehouse includes about 42,000 square feet of office space with the remainder of area is used for warehouse activities. Around 2023, significant structural settlement at the floor slabs of the office area and western half of the warehouse was documented in a structural report indicating slab settlement up to 1 inch had occurred in the office area and cracks up to ¼ inch in width were observed in the office and western warehouse floor slab. A settlement monitoring plan was initiated in 2024 to document the rate of slab settlement. Twenty monitoring locations were established in the west area of the structure with monthly settlement readings over a 6-month period showing no discernable trend in settlement.

Three soil borings were advanced in the western half of the warehouse which showed about two feet of fill underlain by very loose to loose sand to depths of about 8 to 18 feet where medium dense sand was encountered to the termination depth of borings at 25 feet. Groundwater was observed at depths of 8 to 9 feet below the slab. Based on the slab settlement and weak bearing soils several repair options were included in the geotechnical report. The repair options included surficial leveling of the existing slab, low mobility grout columns, polyurethane foam injection, removal and replacement of the upper soils and slab, or installing a deep foundation system with a new structural slab.

Solution

Because of the concerns for shutdown of the warehouse operations during repairs, most of the repair options were not feasible. Polyurethane foam injection was selected as the optimum repair option given the ability to perform the injections quickly with little interruption to warehouse activity. The foam injection was also the most cost-effective option. A combination of deep polyurethane foam injection to improve the bearing soils to a depth of 10 feet along with shallow injections to lift the slabs back to original elevations was recommended. Foundation Supportworks® PolyLevel® foams are extremely light, with different formulations weighing between 2 to 4 pounds per cubic foot (pcf). Foundation Supportworks® PolyLevel® PL400 mixture was chosen for the application. PolyLevel® PL400 has a typical compressive strength of 60 to 70 pounds per square inch and a free-rise density of about 4 pcf.

The scope of work for the warehouse area included injection locations on approximate 4 to 5-foot centers across a treatment area of about 3,800 square feet. The deep foam injections started at a depth of 10 feet below the slab and the foam injection continued as the injection tube was raised to a depth of 5 feet. The amount of foam injected in the deep zone at the warehouse area totaled 9,400 lb of material at 235 injection locations. The slabs were lifted using a similar injection spacing and totaled 2,450 lb of PolyLevel® foam. The office area deep soil treatment consisted of 50 injection locations on 4-foot centers across an area of about 950 square feet. The deep injection foam was installed at the same depths and methodology as the warehouse area and totaled 2,500 lb of PolyLevel® foam. The foam injection for the slab lifting at the office area was performed at similar spacings as the deep injections and totaled 700 lb of PolyLevel® foam. After lifting the slabs back to the original elevations, the larger cracks and spalled areas were leveled with epoxy grout. The quantity of PolyLevel® foam for the entire project totaled about 15,000 lb and the work was completed over a 9-day period.