Ground engineering contractor Central Piling has solved a deep foundations challenge at the former Erith Quarry site in south east London.

The regeneration project, named “the Quarry”, is being delivered by a joint venture between developers L&Q and Anderson. Once completed, it will include 849 new homes, a new primary school and a 4.9ha ecology park.

In total, the scheme covers an area of around 20ha on the site of the disused quarry. When quarrying ended in the 1960s, the site was filled in with rubble and waste materials. The joint venture secured planning consent for its regeneration proposal in 2015.

As part of the latest phase of the project, Central Piling began working on site last year. It is installing piles to support the new development.

Due to the nature of the site, the ground conditions are highly variable, with large areas of mixed fill reaching depths of up to 30m in some places.

As a result, the challenge here is to install piles that are deep enough to reach firm ground, meaning some need to be up to 40m in depth.

Central Piling managing director Steve Hadley said: “Rotary piling wasn’t feasible due to the depth of casing required, and driven piling might not have penetrated harder elements within the fill.”

Instead, Central Piling chose to use the continuous flight auger (CFA) piling technique. However, this brought up a new challenge: few CFA piling rigs can drill down beyond 30m.

“There are rigs that can drill to about 36m, but they are huge 120t machines,” Hadley noted.

Central Piling has overcome this problem by deploying two piling rigs working in tandem. Both are Italian made Soilmec machines, an SF-50 and an SF-65 rig.

The larger of the two rigs, the SF-65, is used to install the first stage of the pile. “This is the main machine,” said Hadley. “It can drill down to 29.5m”.

Once the SF-65 has drilled to about 24m, it decouples and backs away to allow the smaller SF-50 to position itself over the first auger, to which it couples its own auger. This machine then continues the boring process to reach the required depth.

“This presented a safer and higher production solution than adding single 6m sections of auger to a single rig,” Hadley added.

Nevertheless, to make this system work, Central Piling had to develop a special tool for supporting the drilling tools as the rigs were swapped during the concreting stage of the operation. The team also configured the drum and pump set-up with a valve that allowed concrete to be shared between the two machines.

Even if a 120t rig had been available, Hadley doubts it would have proved suitable for this site.

“It’s quite tight in some places but having two machines that can move independently means we can get into those spaces,” he said.

He added: “I’ve never heard of anybody using two rigs in tandem like this – as far as I know, it’s a first.”

Central Piling has encountered some unforeseen conditions during piling.

“We did encounter some locations of deeper fill as well as some voids,” Hadley explained. “This necessitated close inspection of the arisings and a suitable adjustment to the design length [of the pile].”

When such conditions arose, Central Piling had to adapt its procedure. This involved, for example, altering extraction rates to maintain concrete pressure and pumping additional concrete to fill voids to ensure successful results.

“In some places we had to re-drill in order to install viable piles,” Hadley said. “Of course, our client understood the variability inherent on this site and were accommodating to these changes.”

Work on the Quarry redevelopment is expected to be completed in spring 2026.

Want to read more? Subscribe to GE’s enewsletters and follow us on Twitter and LinkedIn

Tagged with: Central Piling CFA Piling quarry regeneration

Foundation engineering company Bauer Spezialtiefbau is installing bored piles on an excavation…

Sheet Piling UK is carrying out works as part of a £10M…

Italian soil engineering specialist Trevi Group’s Algerian subsidiary is working on foundations…

Van Elle has reported a full-year pre-tax profit for the first time…

Sign in or Register a new account to join the discussion.

Business, International, Project, Industry, Weekly