Sinkhole Repair - Soil Densification & Improvement

The horizontal mine shaft found 50 feet beneath the home of the Mark Kempner family in Rockaway, New Jersey has been said to be of the highest quality iron ore ever extracted in North America.

While the mine was to have been filled with a flowable fill circa the Revolutionary War, certain voids allowed for a yield in the overburden, which subsequently collapsed into the mine’s voids. At grade, there appeared a void beneath the slab-on-grade home, measuring 15 feet in diameter and 15 feet in depth: thereupon, a Rockaway contractor- Mazzola Construction—installed lolly columns and four-by-fours as a tempo- rary means of support.

CTL Engineering of Morgantown, WV — specializing in mining consulting and mine forensics — put together a solution after having studied the Kempner residence challenge. Mazzola Construction was to fill the sink hole beneath the home with flowable fill. However, given the known weight of such a mass, a polymer support matrix beneath such a mass was to be created by URETEK ICR Northern US. The unique nature of the Uretek polymer material would offer CTL the desired soil improvement at depth, while creating a bridging effect — supportive of the concrete mass.

Because the unique geo-polymer injected by URETEK achieves 90% strength within 30 minutes of injection and yields a co-efficient of expansion of twenty-to-one, CTL was assured that the URETEK crew could offer the kind of control and predictability needed for such a support matrix and soil improve- ment. Moreover, the strength-to-weight ratio is such that the cured polymer offerd CTL the desired compressive strength, while adding only minimal weight to overburden soils. URETEK ICR Northern US worked the job under the direction of Bob Dandy and John Linke: with a combined 17 years’ Uretek experience.

The job was done in 3 phases:

Phase 1: The flowable fill by Mazzola Construction.

Phase 2: The soil improvement by URETEK.

Phase 3: The URETEK Method was injected through holes previously drilled in the home’s slab to fill all voids & fully restore the base beneath the Kempner home so that the cured fill material would make contact with the home’s slab.