Challenge
Ground beneath the raft slab had settled adjacent to a deep drainage ditch, causing differential movement, structural cracking, uneven floors and damaged tiles while occupied by the tenant.
Solution
Geobear installed 41 geopolymer injection points beneath the floor slab, filling voids, strengthening underlying fill and precisely re-levelling the slab within one day with minimal disruption to occupants.
Project duration
injection points
Spacings
Geobear was appointed by a contractor working on behalf of a regional housing executive to resolve subsidence affecting a mid-terrace, two-storey residential property in Co. Derry.
Significant structural movement had developed within the ground floor slab, resulting in extensive cracking to the right-hand elevation of the property. Cracks were visible internally and externally, while differential settlement had caused uneven floors and cracked floor tiles.
The property was constructed on a raft foundation and the affected side was located adjacent to a deep drainage ditch. Over time, ground movement beneath the slab had caused the supporting fill material to settle, leading to loss of support and movement of the floor slab.
A rapid, cost-effective solution was required that would minimise disruption to both the tenant and the housing provider.
The principal alternative was to remove and replace the entire ground floor slab. This would have involved extensive excavation inside the occupied property, significant construction work and a programme of at least three weeks.
Replacing the slab would also have required the tenant to vacate the property, increasing costs through temporary accommodation while creating considerable disruption for everyone involved.
The challenge was to restore the slab's support and level without excavation, demolition or prolonged displacement of the resident.
Customer testimonial
Geobear designed a geopolymer injection solution to stabilise and re-level the affected floor slab.
A grid of 41 injection points was installed across the slab at approximately 1 metre centres. Through small drilled access holes, a precisely controlled quantity of expanding geopolymer was injected approximately 100 mm beneath the underside of the slab into the underlying fill material.
As the material expanded, it filled voids, strengthened the weakened ground and carefully re-levelled the slab where required. The lightweight geopolymer restored support without adding significant load to the underlying soils.
The entire stabilisation programme was completed in just one day, eliminating the need for excavation, slab replacement or heavy construction equipment.
The floor slab was successfully stabilised and re-levelled with minimal disruption to the occupied property.
Compared with traditional slab replacement, the Geobear solution delivered substantial programme and cost benefits:
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