Thrasher Foundation Repair Case Studies: Slab Pier Solution Used to Stabilize Facility

Challenge

A large electronic equipment component manufacturer had an area of their building that was experiencing extensive settlement.  It was particularly evident in a 130” section of hallway adjacent to an addition that was added on to the structure. This section of the building showed 2” of settlement from side-to-side in a five-foot wide hallway due to the poor compaction of the soil. The slab settlement caused trip hazards at each end section of the hallway, dry wall cracks, broken floor tiles and doors becoming out of plumb and not function correctly.  This area of the plant was in the heart of the facility, so access for equipment was very limited. It was crucial that the hallway stay open during installation due to the high volume of foot traffic in that area.

Solution

Because of the limited access and the type of installation that was required, it was determined that a slab pier system was an ideal solution to lift and permanently stabilize the slab in this area of the facility. This system can achieve relatively high capacities with the versatility to be installed in limited access areas like the hallway of this facility.  The design included 18 Model 288 (2.875” OD) hydraulically driven slab piers, spaced every 6 feet in line the entire length of the hallway.  Each pier was to achieve a design working load of 18 kips.  In order to install the piers, the 8” thick, wire mesh reinforced floor had to be cored completely through at each location.  Once the coring was complete, piers were driven to the specified pressure at each location. After all of the piers were installed, each of the 18 locations were fitted with hydraulic cylinders connected in series and loaded to a point that the slab began to be lifted, eventually getting back to level. Once the floor was level, there remained a 4-inch void under the slab that was then filled completely with PolyLevel 250H polyurethane foam. 

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