ROCK SOCKET, RETAINING WALL

Acrobatic Work On Platforms

A recent piling contract by Branlow Limited in the North East has involved extremely difficult operational conditions, living up to their reputation of providing solutions on problem sites.

Brought in by Greener Whitehouse Associates, consulting engineers, Branlows has provided an effective solution for ground slippage at the rear of the property.

The existing retaining wall which was holding back the ground at the rear of the detached house was showing signs of slipping down the hillside.  Branlows put forward proposals to relieve the pressure on the wall and ultimately to provide a new means of ground retention at the rear, to protect the property in the future.

The pile solution involved drilling 3-4m through the overburden and providing a 4m rock socket in the underlying mudstones.  Pile diameter was 220mm with a rock socket diameter of 170mm.  The total length of the retaining wall was 17m. The piles were reinforced for their full depths using 75mm diameter 5mm thick circular hollow sections and a high strength cement/PFA grout.

Branlows' operatives had to work in a very tight environment - the contract was undertaken on a steeply sloping site and the rigs had to operate in numerous awkward positions from a platform only 1.5m wide.

The project costs of around £100,000 also included some traditional mass concrete and underpinning works for other areas of the property to transfer the existing foundation loads to the underlying bedrock.

Additional investigation revealed the presence of significant voids underneath the existing concrete retaining wall.  We cored through the existing reinforced concrete base on a 1.5m square grid and pressure grouted any voids encountered, using a cement/PFA grout.

Produced by client Greener Whitehouse Associates