Stabilization of weak foundation and lifting of floor structures

Summary

The problem was that this factory canteen had subsided due to weak sub-base soil. The consequent subsidence had created dangerous trip hazards at several locations and had fractured many floor tiles. This situation was corrected with GeoResin polymer piles driven into the areas of weak soil to re-establish proper building support and raise the floor back to level. With no excavation, mess or building damage, all areas were brought precisely back to design levels. The rectification was extremely rapid, just seven days, and caused only very minimal disruption to the factory and staff.

Objectives

The primary objective was to compact the weak foundation soil areas, and so strengthening them to provide the support required to allow the floor to be raised and re-levelled. The secondary objective was to do this economically and in the fastest and least intrusive way possible.

Solution

Our Dynamic Cone Penetrometer (DCP) testing determined that the foundation soil was very weak at depths between 1m and 3m. Traditional methods of creating foundation ground support, inserting piles through the floor or injecting massive piers of low mobility cementitious grout are both extremely damaging to a floor and very time-consuming, disruptive and expensive.

To avoid those problems, we chose to use GeoResin polymer piles. They were inserted through small diameter holes, 32mm Ø, and injected with GeoResin resins that expanded up to as much as 400mm when in position. They compacted the surrounding soils and remained exactly where they were placed to support the floor. Having expanded more in the weaker strata and less in more dense soil, they keyed into the ground, bridging over the weak soil and thus connecting the floor to the more dense soil.

57 polymer piles were installed, each 2.5m in length. They were positioned to bridge the weak strata beween 1m and 3m below the surface.The floor was re-supported and precisely re-levelled in just seven days. There was minimal mess and disruption and the project came in on budget for client.