Tunnelling experts this week questionned
contractors decision to use the New
Austrian Tunnelling Method (NATM)on the
section of the Sao Paulo Metro that
collapsed earlier this month
They pointed out that ground conditions made NATM a risky tunnelling
option, especially as the city has a
history of similar failures.
The collapse on 15 January at the
site of the Pinheiros station near Sao
Paulo University resulted in the death
of seven people.
The tunnel failure occurred close to
a junction with a 40m diameter, 40m wide
deep access shaft whose sprayed concrete
wall also collapsed.
It was the fourth NATM collapse on
the Sao Paulo metro in four years.
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