Urban EPB shield · Ø 7.08 m

Analytical (browser)

Operator

Chamber pressure (bar)

Alarms

Cycle

Advance with downtime

Thrust and torque

Segment lining

Ring forces by the elastic equation method (ITA WG2 2000) with Wood's joint reduction; jacking, bursting and grout checks after ITA (2000, 2019) and DAUB (2024). Ground stiffness, concrete modulus and the shoe pad are assumed.

Geological long section

14 Crossrail boreholes from the British Geological Survey (Open Government Licence v3.0; contains British Geological Survey materials © UKRI 2026). Unit parameters from open sources, some assumed; the tunnel level is an assumed alignment within the published depth. Details: scenario format and sources.

Ground and surface

Model limits

  • Volume loss is the measured Crossrail value (Ground panel), raised where London Clay is at the axis when the face pressure drops, by Macklin's (1999) load-factor relation; it never falls below the measured value and does not respond to grouting. Undrained strength is the Crossrail Paddington design profile carried along the line. One bore is modelled.
  • Buildings: OS OpenMap Local footprints (terraces merged into blocks), heights from Environment Agency LIDAR, listing from the National Heritage List for England, all under the Open Government Licence v3.0. Contains OS data © Crown copyright and database right 2026; © Environment Agency copyright and/or database right 2026; © Historic England 2026. Damage uses the greenfield trough under each footprint, without building stiffness.
  • Building categories come from the second-stage assessment of Mair, Taylor & Burland (1996, ISSMGE library): the building follows the greenfield trough, and each hogging or sagging span's bending or diagonal strain (from Δ/L, as a masonry deep beam, E/G 2.6) is combined with its average horizontal strain. That is conservative: real buildings are stiffer. Each building also shows its Δ/L and largest horizontal strain with an estimated stiffness (Potts & Addenbrooke 1997, as plotted by Mair 1997; 1996, Fig. 5), from floor slabs every 3.4 m acting together (an assumed upper estimate). These are shown only; they do not change the category.
  • Downtime uses distributions fitted on one 6.88 m metro EPB (Tabriz; Moosazadeh et al. 2018) and a published shift pattern; they are illustrative for other projects. Locomotive travel time, learning curve and ground-related stops other than tool interventions are not modelled.
  • Chamber volume, screw efficiency, friction coefficients and machine weights are illustrative assumptions.
Models: wedge-silo face support and DAUB window, chamber volume balance with foam, simplified screw (Merritt & Mair), thrust and torque components (Shi et al. 2011), Gaussian settlement (Peck; O'Reilly & New; Mair & Taylor), utilisation and downtime (Moosazadeh et al. 2018; record rates with sources). Machine class from published references.