6 October 2021
Heishui: a rockslide at a tunnel portal in Sichuan Province, China
Posted by Dave Petley
Heishui: a rockslide at a tunnel portal in Sichuan Province, China
Loyal reader Mark Shore has kindly highlighted an interesting rockslide that was caught on video in Heishui County, in Sichuan Province in China. The landslide apparently occurred on 30 September 2021. The two tweets below capture the event:-
https://twitter.com/timbaland57/status/1443838235327803399
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https://twitter.com/meteoredit/status/1444006701145993219
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Whilst the video below captures the aftermath and, at the end, some further landslide activity:
https://www.youtube.com/watch?v=FDTO267hSJo
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Clearly this type of event is exceptionally dangerous – it is perhaps surprising that there is no apparent landslide mitigation on the slope or around the portal given the obvious potential for rockslides at this site. According to a report in NTDTV.com, in Mandarin, the landslide occurred at 9:20 am at the entrance of the Xi’er Tunnel of National Highway 347 in Heishui County, Aba Prefecture, Sichuan. There were no casualties, but a transformer and a car were damaged.
Some reports suggest that an accident was avoided because a security officer at the site raised the alarm.
Mark has identified the likely location for the landslide, which is at 32.080° N, 103.181° E:-
Google Earth image of the location of the 30 September 2021 rockslide at Heishui in Sichuan Province, China.
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Clearly this is a location with a high incidence of landslides, but it seems like that the slope above the tunnel portal shown in the Google Earth image has been quarried.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
Wow! In my experience, tunnel portals are the most dangerous locations for any tunneling project – during construction or after commissioning. I have seen several examples of tunnel portals where the risk of rockfall was so extreme that entrance to the portal area had to be closed permanently, or the portal area had to be closed temporarily to install significant rock support.
The one major lesson I have taken away from my involvement in tunneling projects is that regardless of the preferred tunnel alignment, the portal orientation should be optimized so that the effect of discontinuity orientations can be minimized so that rock support works can be minimized and a safe working area created. It’s when the portal orientation is not optimized that problems occur, and mitigation works after construction has started can be expensive, and regardless of cost, must be completed so that the project does not get shutdown or outright cancelled.
Again, as every other time, thanks for sharing Dave!!!
If you enter Xier Tunnel Sichuan on Google Maps when on the location the panel on the LHS has a link to a CTGN news website in English with a video clip which towards the end has a close up of the portal after the fall showing the debris. In the debris appears to be the remains of a chain link fence or similar which presumably was intended to catch falling rock.