Concrete Stabilization Technologies, Inc. was contacted by Mr. Bill Sublette P.E., Owner of Foundation Stabilization, Inc., Las Vegas, NV concerning the multi-unit Fox Hall Apartment Complex at 1600 E. University Avenue in Las Vegas. Mr. Ed Russ had contacted Mr. Sublette concerning the remediation of this property. Mr. Sublette in turn contacted Roy Mathis of CST for help in determining the best solution for repairs of the property, utilizing the advanced CST Technologies.
The complex had experienced significant distress and settlement due to the solubility of subsurface soils which had produced a significant settlement of 6.25 inches on the one corner of the building and a differential settlement of over 5 inches of the concrete floor slabs. Initially one unit of the complex was identified for repair. Two additional units were also included in the project.
Factors for Consideration
Significant distress of the property had occurred due to the solubility of the subsurface soils. Settlement differential of over 5 inches on the concrete floor slab and exterior footings had produced cavities or voids in the underlying subsurface soils. Stress on the slabs had not only produced significant cracking in the interior and exterior walls and floor slabs, but also caused problems with waste lines and exterior walkways of the units. Three options were considered for repairs. Helical Piers. Micro Piles, and CST’s deep injection process.
The foundation remediation for the Fox Hall Apartments utilized injection of CST Expanding Structural Polymer in the top 5 to 7 feet of sub grade soil beneath the exterior continuous wall footing and interior slabs. The injection of the CST ESP densified the soluble silty sands and clays in the top 5 to 7 feet of sub grade soils beneath the load bearing foundations and the result was lifting of the load bearing foundations. Additionally, areas under the distressed slab were injected with CST ESP to lift and re-level the concrete floor slabs, and densify those areas of the subgrades that had low densities and porosities (voids). The process filled the voids without adding additional weight. The ESP works to interlock soils in place, and the impervious nature of the product helps to prevent future water migration into the soils which would prevent any future extension of soil collapse.
Areas of low density beneath the slab were determined by using a dynamic field penetrometer. The process was coordinated to minimize cracking in the floor slab and to ensure that the floating foundation was not lifted off the exterior continuous wall footings interior notch.
Multiple locations and depths were injected and voids filled beneath the floor slabs. Full time observation and monitoring of the injection and lift were necessary to ensure no additional cracking of the floor slabs in the units.
Three apartment units were successfully repaired with one corner of the foundation being lifted 6 1/4 inches and another corner lifted 3 1/2 inches. Voids were filled and soils stabilized beneath the concrete slabs. Slabs were realigned and lifted to original grade with minimal disturbance to tenants and landscape features. The original integrity of the uniform foundation system was maintained by utilizing CST’s technologies. Work was completed in less than a week and the owner and manager of the property was very pleased with the result.
Time Savings: Repairs were made quickly. The non-intrusive nature of the repair process resulted in minimal disturbance to landscaping & tenants of the apartment complex.
Longevity: The integrity of the original uniform foundation system was maintained by using CST’s Technologies. The foundation lift and stabilization were made without mixing a deep foundation design with the original spread foundation. The migrating nature of CST Expanding Structural Polymer not only filled voids, but interlocked soils, helping to increase stability of sub grade soils. The impervious nature of the material will prevent future water migration into the soils & prevent extension of soil collapse.