The assessment of limits for the movement of subway tunnels and trackwork due to adjacent construction

The construction of the North East line has included the excavation of two interchange stations, up to 29.5m deep, near operational railway tunnels. Tunnelling under the operational tunnels followed the excavation. A detailed study of the tolerance of the existing track and tunnel structure to movement was carried out. This study formed the basis for decision making during construction. The methodology used in the study is given in outline. The study also helped to identify some simple measures which could be taken to reduce the risk during construction.