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Demolition of a sports centre in Newport. Requiring complex demolition engineering due to the complexity of the structure, proximity to the main road and basement groundwater.
Client: Newport Council
Demolition Contractor: Walters
Overview
The works were split into four areas:
Sports Hall Demolition (Phase 1)
Admin Block (Phase 2)
Swimming Pool Hall (Phase 3)
Basement Demolition (Phase 4)
Project Complexities and Constraints
The project had several complexities and constraints that impacted on the demolition methodology and the provision of temporary works.
Proximity To The Main Road
The structure was located very close to the main road through Newport, which was to remain active during the demolition. The demolition methodology had to minimise dust and prevent debris from falling outside the site onto the adjacent road.
The road also surcharged the highway, which was a key factor in the decision to deal with the basement during the demolition process.
Structural Complexity & Limited Historical Drawings
The sports hall and pool hall were built with large steel trusses with significant spans.
Due to the lack of historical drawings, a series of site visits, detailed analyses, and engineering knowledge were required to understand how the structures were constructed and their demolition load paths.
Groundwater
The basement was close to a tidal river, meaning groundwater levels could rise and cause flotation or instability in the structure.
Demolition Methodology
Sports Hall Demolition
The sports hall was demolished using a combination of cut and lift and traditional high-reach methodology.
The roof elements were exposed with a high-reach excavator. The large steel trusses were slung from a mobile crane before being cut free with the high-reach excavator. This process was then repeated working into the structure.
Andun provided the sequence for the works and weight estimates for the steelwork.
Pool Hall Demolition
Due to the sports hall’s proximity to the main road and steeply sloping roof, the roof was stripped by hand on the side closest to the road to prevent debris from sliding off.
The initial plan for demolishing the pool hall at the tender stage was to prop the structure centrally and progress the demolition with a high-reach excavator working around the structure.
However, once Walters took possession of the site and allowed detailed opening-up works to be undertaken, an alternative option was developed. The method relied on the perimeter columns, and ring beam.
This allowed the structure to be dismantled working from the centre out, eliminating the central support. This reduced the programme and costs of the work.
The structure was demolished by cutting and lifting sections of the roof and structural elements, starting from the central ring and working towards the perimeter.
This gradual removal of loads from the structure maintained stability throughout the process.
Basement Works
The deepest section of the basement ran parallel to the main road. Coupled with the fluctuation of groundwater levels caused by the tidal river, it made this a challenging aspect of the work.
Instead of fully excavating the old basement, it was decided the best course of action was to open holes in the existing basement, where the new piles were proposed to be bored.
The remainder of the basement was left intact and backfilled. Manhole rings were placed concentrically with the piles, creating a target for the piling works, whilst still allowing the basement to be backfilled. This ensured the walls remained stable, and also prevented any potential buoyancy issues.