Natural Cements Shotcrete 430F dry spray was used earlier in the year to refurbish the Colwall new tunnel one of two tunnels that run under the Malvern Hills connecting Malvern wells in Worcestershire with Colwall in Herefordshire.
The original passenger tunnel was started in 1853 and was opened in Sept 1861. Progress was slow at first as the rock was very hard and the tunnelling was done using mostly local manual labour. However by the 1920’s changes to the speciation of rolling stock meant that the tunnel was too narrow, low and too steep with a 1 in 80 gradient. A new larger tunnel was begun in 1924 adjacent to the original and due to advances in tunnelling techniques was completed and opened on 2nd August 1926.
The old tunnel was closed up until it was used as a naval munitions store during the 2nd world war and is now home to a colony of bats.
The new tunnel has been in operation as a single track tunnel since its opening, it is 1585 yards long the deepest part of the tunnel is 600ft below the surface.
Although Shotcrete 430F can appear to be more expensive per tonne than its competitors it was chosen for this project for many reasons.
Firstly the lack of rebound ensured that over 95% of the material went on the tunnel lining not on the floor of the tunnel.
The high early strength of the Shotcrete 430F also allowed for spraying operations to be carried out nearer to call back time as the product had set & obtained adequate strength to resist the suction from the trains when they were running through the tunnel.
The limited amount of rebound that was produced did not have to be taken to contaminated land fill sites like all the other competitors as it was based on a natural cement and does not contains any chemicals.
The work was carried out during the night in April 2015 by Gunform international Ltd who are approved applicators of our material in collaboration with Keltbray Rail and Geoffrey Osborne Ltd as part of Network Rail’s ongoing refurbishment plans.