Tail Seal Brushes and Grout: Stopping Water Ingress in Water-Rich TBM Ground

The tail seal is the last barrier between a pressurised excavation chamber and the segment ring. Three or four rows of wire brushes, separated by grease injection ports, form that seal; the grease pressure between rows must be held above measured groundwater pressure at the crown. In water-rich sand and rock mixed faces — common on Middle East metro, road and utility drives — one worn brush row can turn a manageable inflow into a serious flood.

Grout does the second job. Annulus grout injected immediately behind the ring fills the overcut void and cuts off the path water uses to reach the tail. Monitor grout volume against theoretical void, injection pressure, and tail grease consumption per ring. Rising grease use with stable grout volume usually signals brush wear, while falling grout volume at steady pressure points to leakage into the tunnel.

For buyers, tail sealing is a consumable strategy, not a one-off purchase. Specify brush wire grade, spring plate stiffness and grease compatibility as a set, keep spare rows and injection port fittings on site, and track wear per ring so replacement happens before a problem. OUSUN supplies tail seal brushes, seals and hydraulic spares factory-direct from Deyang, Sichuan, with typical lead times of two to four weeks.