Numerical Modeling of Underground Metro Tunnels & Predication of Associated Ground Movements-Paper

Paper

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The paper uses two-dimensional numerical modeling to assess construction-stage tunnel lining forces and associated ground movements for a proposed 1.5 km twin-tunnel metro corridor. The tunnels are designed for construction by an Earth Pressure Balance Tunnel Boring Machine (EPB-TBM), with precast concrete segmental linings.<br /><br />The corridor has variable soil profiles, groundwater levels, overburden, and surface loads. Researchers modeled seven critical sections in PLAXIS 2D using the Hardening Soil Small Strain constitutive model. Simulated stages included initial ground conditions, surcharge application, sequential excavation of the two tunnels, lining installation, tunnel volume loss, and tail-void grouting. Rail and derailment loads and a worst-case groundwater condition were also considered.<br /><br />Predicted ground movements ranged from 21 to 56 mm. The largest settlements occurred at two sections in the first tunnel stretch: 50 mm under maximum overburden and 56 mm beneath a 10-storey building. Both exceed the project’s 30 mm acceptance limit, so ground improvement is recommended at these locations. Movements at the other five sections ranged from 21 to 28 mm.<br /><br />The analysis also calculated maximum axial forces and bending moments at the crown, axis, and invert of the tunnel lining for each section. These results can inform the structural reinforcement design of the tunnel segments. Overall, the study demonstrates how staged numerical modeling can identify settlement risks and estimate lining demands where ground and service conditions vary along a metro alignment.

Keywords

tunnel lining forces

ground settlement

EPB-TBM

PLAXIS 2D

Hardening Soil Small Strain

segmental lining

metro tunnel design

tail-void grouting

ground improvement

bending moments