Those dykes on bikes have much to answer for...

<http://www.dailytelegraph.news.com.au/story/0,20281,17871066-5001028,00.html>

'Geology' caused tunnel collapse


January 19, 2006

GEOLOGICAL factors have been blamed for the partial collapse late last
year of Sydney's Lane Cove Tunnel, severely damaging a unit block and
forcing the evacuation of 650 residents.

The tunnel gave way during construction on November 2, opening a
10-metre hole beneath an adjacent unit block in a major embarrassment to the
NSW government, already reeling from anger over the cross-city tunnel.

<snip>

The collapse was caused by "the presence and alignment of a low
strength dolerite dyke", "orthogonal jointing associated with the dyke" and
"the presence of faults which in conjunction with the dyke and the jointing
created unstable ground", the report found.

Water did not contribute to the collapse, Professor Brown found.

Mr Saxelby said the dyke - a vertical intrusion of igneous rock into
the parent material - had not been identified during early feasibility works
but had been noticed later.



<snip>

 

Dykes don't really want you entering their tunnel........