SEM / NATM heading in weak rock · 10 m

Analytical (browser)

Operator

Alarms

Sequence

Ground and lining

Convergence monitoring

Model limits

  • Geology is illustrative (siltstone and a crushed fault zone under 100 m of cover). The horseshoe section is treated as a circle of radius 5 m for the ground response.
  • Lining load from Oreste's (2003) method for a closed ring: in the siltstone, where the ring is not closed early, the load and safety factor are those of a closed ring.
  • Convergence readings use the time law of Sulem et al. (1987) with parameters fitted at one claystone site, scaled to the predicted closure, with ±20 % scatter between sections (illustrative).
  • Cycle times per metre come from Crossrail's Stepney Green caverns (London Clay); rock rounds may be quicker or slower.
Models: Hoek–Brown and ground reaction curve (Hoek), shotcrete ageing and lining interaction (Oreste 2003), sequence by ground class (FHWA 2009), convergence law (Sulem et al. 1987), trigger levels (Crossrail). Method card in the methods reference.