How micron-level CNC machining accuracy prevents gasket displacement, corner spalling, and water ingress under thousands of tons of TBM thrust.
Tunnel segments are assembled directly behind the TBM to form the tunnel's permanent load-bearing ring. A tunnel ring usually consists of 5 to 8 segments and a key segment.
Flawless Gasket Grooves: The EPDM gaskets between segments are designed to withstand water pressures of 8 bar and above. Even a 1 mm error in mould geometry can fold the gasket or prevent full contact, leading to groundwater ingress.
Distribution of TBM Thrust: As the TBM advances, its thrust cylinders push against the segment ring (3,000 to 6,000 tonnes of total force). If the surfaces are not parallel, the force concentrates at a single point and causes spalling at the concrete edges.
Surface Finish: In ARM moulds, contact surfaces are machined in a single setup on 5-axis gantry CNC machining centres. Steel plate thicknesses are optimised against vibration and thermal expansion.