On Thu, 17 Apr 2014 17:57:26 -0500
Recliner wrote:
"The primary cause of the damage was clay shrinkage in the
ground around the tunnel, LU principal tunnel engineer Keith
Bowers told NCE. Other factors, including probable issues with
the quality of design and construction, are thought to have
worsened the problem."

More than likely its 99% the latter given that other lines sitting in the
same clay haven't had problems with their tunnels rings in 100 years.

If you'd actually read the article you'd know it's not quite so simple:

“The alignment of the southbound tunnel was driven by the need to pass
under the Bakerloo Line and as result this section of tunnel on the Jubilee
Line is one of the deepest in zone 1, reaching depths of up to 36m,” said
Bowers.

“This depth takes the tunnel out of the London Clay and into the Lambeth
Group, which is highly variable with sand beds within the clay. It is also
faulted.”

Oh ok, so the problem was clay shrinkage in sand. Right, got it.

--
Spud