Monitoring of Ground Behavior During the Excavation of an Underground Ramp

Abstract

In large cities, underground spaces are gradually limited and interaction between new excavation and existing underground structure becomes a very important problem. The excavation of several underground ramps was launched in Tokyo to link the aboveground traffic flow with underground tunnels. The ramps approach underground twin tunnels and then connect to them. Detailed monitoring instruments were set on the ground surface and nearby tunnels to monitor ground and nearby structures during excavation. The excavation details of one of the ramps are studied. The ramp has a unique spiral curvature in both vertical and horizontal directions. Ground surface instrumentations and monitoring outputs are discussed along ramp alignment before, during, and after passing of the shield machine through several sections. The transverse and longitudinal ground surface settlement data are mainly discussed and interpreted. Also, a numerical model of one of the ramps was created to investigate various influencing parameters and prospect the behaviour of ground-tunnels systems where field data are not available. The predicted results are also limited to tunnelling-induced ground displacement.