Ground movements caused by tunnelling with an earth pressure balance machine: A greenfield case study at Southwark Park, London

摘要

This paper reviews ground movements induced by a 5m diameter earth pressure balance machine at an extensively monitored greenfield site on Contract 105 of the Jubilee Line Extension. Tunnelling was at a depth of 21m through dewatered dense granular soil. Only small ground movements occurred: a maximum settlement of 5mm was observed at the ground surface and 12mm just above the tunnel crown. Movement in front of the tunnelling shield was negligible, most settlement was associated with convergence of soil around the shield and into the tail void. Long-term monitoring has shown no evidence of consolidation; in fact seasonal surface ground movements are of similar magnitude to those caused by the tunnelling. Tunnelling machine parameters measured during the drives are presented and discussed in relation to the ground movements.