Increasing the load-bearing capacity of concrete slabs for York Hospital
Work to build a brand-new endoscopy unit at York Hospital is now underway, and when complete will be one of the most modern and largest endoscopy units in England. It is a £10 million project that is expected to take around a year to complete and will increase capacity from three treatment rooms to seven, reflecting the growing need for endoscopic investigations nationally.
The brick-built York Hospital was constructed in the early 1960s, although many parts have been significantly refurbished since this time. However, the site of the new endoscopy unit will be an additional storey built above the hospital’s existing physiotherapy department, which will be connected into the hospital at First Floor level. This existing building was constructed upon concrete pad foundations and engineering surveys conducted on site found that these existing foundations would not be sufficient to bear the weight of the extra building storey and would therefore require their load-bearing capacity increasing considerably.
With York Hospital a teaching hospital and providing a comprehensive range of acute hospital and specialist healthcare services for approximately 800,000 people, any solution had to be non-disruptive, with little or no impact on day-to-day operations. It had also to be fast and extremely cost-effective.
Kier Construction was contracted to build the new endoscopy unit, with Curtins Engineering the consulting engineers for the project.
There were very few alternative options available to increase the load bearing capacity of the concrete slab that could meet all the criteria; being fast and effective but above all be minimally disruptive on the day-to-day workings of the busy hospital. One option would be the complete demolition of the existing structure and re-build; however the timescales and costs would increase significantly.
For projects such as this, Geobear was the ideal solution to solve the problem presented – that of increasing the load-bearing capacity of the concrete slab foundation to bear the additional weight of the extra building story, whilst also dealing with all the challenges presented of working in and around a busy and live hospital.
The solution offered by Geobear was extremely quick and effective for the type of project, but more importantly had little or no impact on the normal operations of the hospital. It was also an extremely economical proposition.
Our methods are ideally suited to any work site with limited access and where operations need to be maintained. The process we used involved the injection of our Geopolymer material directly beneath the foundation pads.
With our mobile unit adjacent to the hospital building, we could pump material through hoses to the injection points at 40 pads throughout the building. Our highly expansive, yet dense material is injected at multiple points beneath each of the foundation pads, the material solidifies within the ground forming a firmer base for foundations and provides the capacity to withstand additional loads.
Dynamic cone penetrometer tests were used to ensure the requisite improvement to the ground was made. Geobear improved the ground strength to 250 kilo newtons per square metre on 40 foundation pads, meaning the structure could comfortably house the new second storey.