AmcoGiffen has completed a three-month programme of works at Clifton Hall Tunnel in Pendlebury, Greater Manchester.
The tunnel gained notoriety in the 1950s when the collapse of a construction shaft resulted in five fatalities. Four houses on the street above were also lost.
Afterwards, the tunnel was closed and partially infilled but a few voids were left. These have now been filled to ensure the tunnel remains safe for generations to come.
Historical Railway Estate (HRE) engineer Andrew Willison explained: “National Highways took over managing the HRE in 2013 and since then regular safety checks have been carried out at Clifton Hall.
“We decided to fill the remaining voids as a precautionary measure and to ensure the site remains safe for the future.”
Before work started AmcoGiffen used a cavity auto laser scanner, which was lowered down drill holes to provide 3D imagery of the voids.
AmcoGiffen contracts manager Dave Martin said: “The technology is new to us as there are very few of these in the UK. The imagery helped us to calculate the volume of materials required to fill areas of the tunnel with voids present, one of 200 metres long and the other 150 metres long.
“Both sections had five holes drilled that we used to insert the cavity scanner and to pump the materials during the filling stage. In total 2,200 tonnes of material was needed to fill the voids.”
A mixture of cement and fly ash was used in the voids as cement alone would be too strong and would not flow far enough, as it needed to travel 30 metres. Pumping the materials during the filling stage took 10 weeks, working day shifts to keep noise to a minimum for nearby residents.
Constructed in the 1846 Clifton Hall Tunnel, which locally took the name of its dark-whiskered foreman ‘Black Harry’, formed part of the Patricroft to Molyneux Junction line and is a double track horseshoe shaped tunnel measuring 1187 metres long and lined throughout with brick. Its construction was difficult from the beginning as the ground was very unstable where mining had already taken place.
The surrounding area was subject to intense urbanisation with the need for homes being built directly above the tunnel and there were several rounds of remedial works including the addition of steel ribbing to provide additional support.
Following a partial collapse on 13th April 1953 all trains were stopped and inspection carried out. Two weeks later the tunnel roof failed, directly beneath an old construction shaft.
Witness accounts from residents living above the tunnel described hearing a loud cracking noise at 5:35am, followed by two houses, numbers 22 and 24 Temple Drive, collapsing to the ground. Five people were killed and the tunnel was never reopened. It was partially infilled but a few voids were left.
It has taken until 2025, more than 70 years later, for a permanent fix to be carried out.
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