At a state college construction site, the ground posed a karst risk (soil dissolution where limestone rock met other layers), with potential for creating underground voids and caves. Subsurface exploration confirmed void potential and loose soils needing treatment before foundations. Geotech professionals from Helicon were called in for this project.
Initial Assessment
Investigations indicated problematic overburden and voiding at depth. Adding helical piers as a deep foundation solution would extend the schedule by months and inflate costs versus grouting.
Proposed Solution
The contractor selected AP Fill 720 for hydro‑insensitivity, fast adjustable set, and NSF certification to permeate, seal, and lock soils with minimal disruption.
Procedures
- Install 141 grout injection points to depths of 23–100 ft via rotary wash drilling (rotating bit with flushing fluid to clear boreholes).
- Inject AP Fill 720 at maximum depth, raising the pipe in 5-foot increments.
- Complete stabilization using 800 cubic yards of specialized grout mixture.
- Verify soil densification and void elimination throughout the building footprint.
Results
- Zero delays; footprint stabilized pre‑build.
- Approximately 80–95% savings vs adding helical piers.
- Completion in weeks, not months.
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Completion in weeks, not months.