Modelling of ground deformation control induced by slurry shield tunnelling

Ground deformation induced by soft ground tunnelling can cause consequential damage to existing infrastructure if proper controls are not achieved. Highly controlled pressurized face tunnelling combined with tail-shield segment void grouting has yielded significant reduction in ground surface settlement. In some projects, such as the East Side Access Queens Bored tunnels, near zero ground surface deformation was achieved through proper control of support pressures. To investigate TBM control of ground deformation, 3D soil-fluid coupled finite element analysis was conducted with detailed modelling of the construction sequence (such as face and annulus pressure, as well as grout and segment behavior). The findings derived from finite element modelling and the comparison against field measurements identified critical ground deformation mechanisms during pressurized-faced tunnelling. Results show that both the face pressure applied at the cutterhead and the slurry annulus pressure in the shield skin void control the ground deformation during the passage of TBM.