Observed response of maglev structure undercrossed by three shield tunnels in soft soil

Abstract

This paper investigates the response of a maglev structure to three under-crossing tunnels of the Shanghai Metro Line 13. The minimal distance between the tunnels and pile groups of the maglev structure is only 1.5 m, thus the deformations of the maglev structure are strictly controlled for the serviceability of the operating maglev trains. The displacements of maglev piers and ground settlements during different tunnelling stages are monitored with an automatic measuring system. Based on the observed data, the ground settlement trough and displacements of maglev piers caused by the three shield tunnelling procedures are analyzed and discussed. The maximal ground settlement after the completion of the three tunnelling procedures is −43 mm. To operate the existing maglev safely, practical construction control methods are applied, including synchronous grouting, adjustment of the shield status, shield-advancing speed control, and stabilisation of the soil chamber pressure. With these countermeasures, the tunnel-induced deformations of maglev piers are well below the predefined thresholds. All piers heave under the strict deformation criterion of 2.0 mm. The crossing project is finally completed without interruptions of the maglev operations by monitoring the progress. The presented project is a valuable example for the evaluation of shield tunnelling effects on the adjacent maglev structures and establishes criteria for similar projects in the future.

Keywords

• Maglev
• Multi-crossing
• Shield tunnelling
• Ground settlement
• Pier displacement