Monitoring and analysis of deformations and movements of slurry shield tunnel linings

The Qiantang River tunnel, which was planned in 2006 and completed in 2010, is the first slurry shield tunnelling in Hangzhou soft ground, and also the first tunnel under Qiantang River. In construction of this tunnel, in-situ instrumentation was installed to monitor the deformations and displacements of shield tunnellings. This paper analyses the monitoring results in detail. Studies show that: (1) At the early stage after the shield tunnel lining installed, both of its deformation and movement are very small, but they are cumulative with time. So their impacts on ground surface settlements cannot be neglected. (2) After the tunnel lining installed, its horizontal diameter increases in the early time, and then it decreases gradually till it comes to a certain value. (3) Early after the tunnel lining being installed, due to buoyant force of synchronized grouting fluid, underground water and slurry fluid, the lining will float a little. And then the consolidation of the subgrade leads to lasting settlement of the tunnel lining. (4) Compared with ground surface settlements, those of the crown of shield tunnel are much smaller. The movements of the crown of the tunnel and ground surface have positive correlation, and the settlement of the crown will increase the ground surface settlement.