The challenge
Part of a gravity river wall alongside the River Tame near Birmingham, collapsed in December 2020. The site features an access road for an industrial unit, which runs parallel to the river, itself flowing under the Bromford Viaduct of the M6 Motorway adjacent to the site.
Overhead high voltage electricity cables located immediately above the affected area provided an added challenge, along with hard ground conditions.
The solution
We installed a steel sheet pile river wall to close the gap in flood defences, replacing the failed section. Following this, a line of raked concrete piles were installed, each receiving a steel universal column cast into the bored pile.
To overcome difficult soils in an area already vulnerable to vibration, Giken Supercrush (a vibration-free installation method, whereby hard ground is augered as piles are simultaneously pressed in) was selected to install the replacement retaining wall, comprising 107No. AZ28-700 steel sheet piles.
Later, 49No. 450mm diameter concrete piles were installed using the CFA method (piles drilled and concreted in one continuous operation), with steel universal columns integrated into the cast concrete, all raked on a 10˚forward incline. This was carried out using our 50 tonne Kobelco excavator, equipped with drill mast, which allowed us to work at a reach, with the base machine able to stand further back than a standard leader or bored piling rig to install the raked CFA piles.
The raked piles, installed alongside the vertical sheet pile retaining wall, provide additional support in sustaining horizontal forces, as dictated by the ground conditions.
