Technical specifications
- 824 no
- Ø 450, 500 & 900 mm
- Max depth of 27 m
The Challenge
This site was logistically challenging, working in and around the four gas holders that were being incorporated into the new structures. This meant limited space and working areas were provided outside of the four gas holders for housing not only site welfare and delivery laydown area, but additionally all the associated elements we require to facilitate our piling works such as concrete pumps, concrete agitator, reinforcement cages and store cabins. Similar considerations were also needed for the groundworks contractor and enabling works contractor where there was an overlap between areas of site.
We also had to consider delivering concrete from pumps located at ground level, down in to the gasholders to service each of the 2 CFA rigs, whilst ensuring any temporary works concerns in relation to fixings of concrete pipework and the brick clad gasholder walls were overcome.
The Solution
With the collaboration of contractors working together and detailed planning ahead of mobilisation, we successfully mobilised a Soilmec SR75 and Soilmec SF55 to site, chosen for their size and depth capabilities to Install 824No. piles split between the four gas holders, with access ramps constructed down in to each gasholder and moved as the piling works proceeded.
Given the varied condition of the relic brickwork gasholder walls, we concluded that it would be more practical and reliable to develop a concrete delivery frame that enabled concrete pipes to be set up between ground level and base of gasholders (up to 7m down) without the need to rely on bolting or connecting to the brickwork in any way. This frame was specifically designed to vary in height to match the gasholders and be set up in to place using a handling crane and kentledge blocks.
This did not alleviate the requirement for temporary works, however it meant that reliance was placed on known materials with known strengths compared to a relic brickwall with unknown strength characteristics.
A high grade mix of concrete was required for the 900mm diameter tower crane base piles as this was to form the piled foundations for one of the largest capacity tower cranes in the country and be operational within a condensed timeframe.
