The client required ground improvement to soils beneath the existing foundations of a former school building that was in the process of being converted into a hotel.
As the refurbishment was underway cracks started to appear on the walls. Initially, monitoring was conducted and superficial works were completed, however, a number of months later it was found that the structure was still moving. Consequently, Geobear was contacted to provide ground improvement to stabilise the gable and rear walls to improve bearing capacity.
Following a review of all existing site information provided for this scheme, it was evident that the underlying issue was related to a material washout due to poor drainage. This was evident from the presence of standing water in the drainage system and the increase of soil moisture content with the increase in depth. The washing out affected the material below the foundation at a depth of 1m, where the soil is logged as loose sand.
A piling solution to the existing foundations was an alternative solution. However, this approach would have taken months and pushed back the schedule. This would have added notable costs to the programme and affected multiple trades.
As the requirement for this project only presented itself whilst the conversion works were taking place, a fast solution was urgently required to keep the overall project to programme.
Geobear’s methodology also enabled the teams to work with restricted access, there was a road adjacent to the building and concerns over local disruption as this was the main access route. Geobear could work within the basement area of the building, whereas piling would have required outside working and full road or lane closure would have been necessary.
The Geobear solution featured the injection of a specialist geopolymer resin to a depth of 2 metres below the existing foundations. The resin was injected at several depths at points along 24m of the gable and rear wall of the building.
The resin was pumped into the injection locations from a self-contained unit. A two-component liquid material is injected which results in a chemical reaction and expansive geopolymer resin. The resin expands in the existing soils filling microvoids and compacting the area. The result was a strengthened sub-base to the existing foundation at an allowable bearing capacity of 160kPa.
Geobear delivered this job in four working days resulting in minimised delays to the overall programme.