Going underground

摘要

This is the inside of Netherton Tunnel as work progresses on major repairs to a section near the centre of the 3,022-yard tunnel. The work has been planned since the tunnel was identified over 18 months ago (see our feature, Sep 2011) as the only one on the network suffering from active movement. The sides were being pushed inwards by lateral pressure on the walls, resulting in the crown of the arch cracking. The repairs have involved excavating the twin towpaths and inserting two lines of five metre ground anchors on each side, one set to resist lateral movement and the other to provide vertical support, before reinstating the towpaths in concrete.