Poor ventilation of the London Underground in the UK is a major problem, particularly on the deep tube lines. Heat sources include electrical cables, train motors, platform lighting and signage, escalator motors, and the passengers and staff. Heat build up has caused temperatures to rise up to 40 C. The only significant means by which the deep tube railway network is ventilated and cooled is by the piston effects of the trains on the line. The deep tube network has 120 tunnel cooling fans to remove heat from the tunnels when trains are not running at night. A draught relief system is also present. A solution based on Artificial Ground Freezing (AGF) has been proposed. This operates as a closed loop that delivers an injection of cold air into the tunnel ahead of an oncoming train. The AGF would be installed entirely from underground openings constructed in the London Clay off-line from the live railway. The ground freeze would take place mainly in the Upper Chalk aquifer. The principles of AGF are outlined. The ways in which cooling load requirements would be met and the delivery of cold air to the underground network are discussed. (Author/publisher).
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