Automatic monitoring and control of excavation disturbance of an ultra-deep foundation pit extremely adjacent to metro tunnels

Abstract

This paper proposes an automatic monitoring and control system to control the construction disturbances of an ultra-deep foundation pit extremely adjacent to the operational metro tunnels. By real-time monitoring the structural response of tunnels and foundation pits, the reinjection wells and servo support system were automatically controlled to change the groundwater level and support axial force, respectively. All the relevant monitoring and control equipment was integrated into the system through Internet of Things technology. The field observations revealed that the proposed automatic monitoring-control system and framework can well control the excavation disturbance in adjacent metro tunnels. Under the ultra-deep excavation depth of 42.25 m and ultra-close spacing of 3.0 m, the maximum absolute value of the observed tunnel displacement was less than 5 mm. All the relevant structural responses of the tunnel and foundation pit were within limits. The wall deformation of the servo side is different from the common bulging deformation curve and is approximately 2 times smaller compared to the non-servo side. The observed tunnel deformation mainly changed at the excavation stage within the buried depth of tunnels. The presented system, data, advised control index and framework can provide useful guidance for similar scenarios.