Treating subsidence

When its warehouse in Ireland continued showing the impact of severe and continued subsidence, Hosetech chose resin injection, rather than traditional piling, to treat the problem. Teretek geopolymer resin injection technology from ground engineering specialists Mainmark, provided a quick, cost-effective subsidence remediation and slab floor re-levelling solution when compared to the more disruptive traditional deep piling.

Hosetech assessed three options available to them: demolish and rebuild the warehouse with new deep piles; re-piling of the warehouse foundations; and geopolymer resin injection technology.

Hosetech were looking for a solution that could treat the symptoms of subsidence in the sinking warehouse floor in the shortest possible timeframe and with minimal disruption to business operations. Resin injection technology fitted the bill on both counts.

The technology works by injecting a liquid mixture of a resin and hardener into the ground where a reaction between the two causes the liquid to expand and set quickly. During this expansion, the geopolymer resin fills any voids, cracks and discontinuities within the ground. When applied under floor slabs, the expansion of the resin compacts the loose soil under the slab, creating a denser soil matrix. Through carefully planned resin injection sequencing, the ground conditions beneath the warehouse floor were improved and the required lift was achieved in designated areas to address the unevenly sinking concrete slab. The whole process took a little over three weeks.

As the work was carefully planned to be carried out in sections of the warehouse at a time, the business could continue to operate.

Hosetech head of purchasing Nathanael Ottman, says: “Addressing the sinking warehouse floor was the number one priority for the business and resin injection technology gave us a way to achieve this and keep the business running at the same time.”

The geopolymer Teretek resin was delivered through injection tubes driven into the ground through 16mm holes drilled into the concrete slab. A controlled quantity of resin was injected at each location and lasers were used to check that the right amount of lift had occurred.

To prevent putting the concrete slab under undue stress, not all the resin needed achieve the specified lift at each injection point was delivered in one operation. The process had to be repeated at each location in stages, to lift the slab gradually and under monitoring, until the targets had been met. In all, more than 800 separate injections of resin took place and, in some positions, lifts as high as 300mm was achieved.

For more information, visit www.mainmark.com