Cockett Tunnel was constructed in 1852. The tunnel suffered a partial collapse in 1899, which was believed to have been caused by the recommencement of pumping operations at the long-closed Weig-fawr colliery.
The tunnel was completely closed for four weeks, after which traffic was resumed on a single line, but it was not fully restored until 1903, by which time steel ribs had been inserted into the bore of the tunnel at its eastern end (not the location of the collapse) to strengthen the roof. These were found to unduly restrict the loading gauge within the tunnel and were removed in 1908.
At the same time the eastern end of the tunnel was opened out (reducing the length to 789 yards) and the cutting sides were supported by two brick-built flying arches preceded by a very short tunnel. The banks of the cutting were so unstable that even during this opening-out work, timber horseshoe shoring was required.
Our team carried out a detailed Bore and Portal exam over 2 cold nights, using RRV, lighting and hand tools. The tunnel walkover was completed during the daytime in full sun.