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Monday 28 Jul 2025

Trains running through the Blackheath tunnel again following pioneering repair work to boost performance

Region & Route:

Southern

10-week programme of essential repairs on 175-year old Victorian structure comes to an end as trains between Blackheath and Charlton stations resume.

The South Eastern Railway has completed a 10-week programme of essential repairs in the historic Blackheath tunnel between Charlton and Blackheath stations that will help to improve reliability and safety for passengers.

Services return to the normal timetable from today along the Woolwich and Bexleyheath routes following the re-opening. There will be two trains per hour to Cannon Street via Charlton and Blackheath stations, which previously ran via Greenwich when the tunnel was closed.

The 175-year old Victoria-era tunnel has undergone a pioneering strengthening and waterproofing process, believed to be the first of its kind in the UK and potentially the world.

Engineers injected expansive grout into the pockets of sand and gravel surrounding the tunnel to strengthen the ground. This innovative technique knits and compresses the loose material tightly together.

A further layer of grout was applied to the back of the tunnel lining to waterproof the worst-affected areas, helping to preserve the brickwork and track, signalling, and other railway equipment in the tunnel for years to come.

The techniques trialled and used successfully in the Blackheath tunnel during this closure will now be replicated across other parts of the rail network.

David Davidson, chief operating officer for the South Eastern Railway, said: “Over the last 10-weeks we’ve completed a groundbreaking programme in the tunnel that will improve reliability by strengthening and waterproofing the structure to better protect the railway.

“Savings from this approach are estimated to be around £10 million and this can be reinvested across the network to deliver more improvements that will keep passengers moving.”

“Last summer our engineers cleaned soot from the tunnel lining, carried out detailed surveys and replaced thousands of bricks to stop water getting in. This year we’ve installed a new tunnel lining, rebuilt drainage systems and completed essential track work, including the removal of the waterlogged sections known as ‘wet beds’.

“I want to thank our customers for bearing with us while the tunnel was closed for this work to deliver better journeys.” 

Engineering by numbers:

• 1,000 core holes drilled, stretching 900 metres – three times the height of The Shard or the length of Greenwich Park
• 4,000 injection tubes installed, totalling 13 kilometres – enough to reach from Blackheath tunnel to London Zoo
• 55 tonnes of grout used – equivalent to the volume of two swimming pools
• Tunnel monitoring system detects movement to 0.01 millimetres – less than the thickness of a human hair
• Peak workforce of over 100 people working day and night