HS2 Sinkholes Buckinghamshire


Well-known member
Why do these make the news when they're in a field? Did they stupidly promise it wouldn't have any impact anywhere?

They just need a few tipper trucks of chalk to fill them back up. If they appear under someone's house then maybe local newsworthy, but a dip in a field??? If you excavate millions of tonnes of chalk there's bound to be the odd flash/dip topside especially in chalk which can do that naturally anyway, to a lesser extent.

Genuinely puzzled why these make the news. I find it interesting because I'm an underground nerd, but "normal" people this is no relevance

Andy Farrant

Active member
HS2 have been pretty lucky with these; had they occurred beneath an urban area, the consequences could have been more serious. There have been four sinkholes now. All are in areas where the potential for over-break was known, either where tunneling through areas of weak ground due to faulting (the Shardeloes sinkhole near Amersham) or areas where deep sediment filled dissolution pipes were known or suspected to occur (Hyde Heath). HS2 would have been aware of the potential hazard.


New member
Luck or planning? Had the geo risk been in an area with high consequence for any significant over-break then presumably some mitigation measures would have been employed, such as compensation grouting, such as was used extensively for construction of Crossrail and Jubilee Line under London in recent years.


Active member
I am unconvinced that route planning for HS2 always took adequate account of geological hazards. In Cheshire a significant section of the route planned in January 2013 had to be re-aligned in November 2016 as it failed to take account of salt extraction and the after use of resulting cavities.

(Of course, the whole of this part of HS2 has now been abandoned.)