The Qing-chun Road Cross-river Tunnel is the first road tunnel under the Qiantang River in Hangzhou, and it is also the first experiences of slurry shield tunnelling in Hangzhou soft ground. In order to ensure the safety of construction and reduction of environmental impacts while shield tunnelling, a comprehensive monitoring system was carried out during construction, which included ground settlements, displacements and deformations of installed linings and so on. In this paper, the long-term ground settlements induced by slurry shield tunnelling were described in detail, and careful analysis of monitoring ground settlements was made. This case study shows that: 1. The surface transverse consolidation settlements do not follow the Gaussian curve; usually the largest settlements exist above the centerline of the tunnel or nearby, from where settlements descend outwards. Due to consolidation, the surface settlement troughs widen with time.2. Shield tunneling in soft ground, the turning point in settlement-time curves or settlement rate-time curves can be chosen as the time divides the immediate and long-term consolidation settlements.
Prediction of ground settlements induced by twin shield tunnelling in rock and soil – a case study
