The collapse of the Dehdasht – Pataveh tunnel portal in Iran

There are two very interesting landslide videos available this week.  One is contained in a Tweet by @GeotechTips showing a rather splendid slump in what appears to be residual soil.  The location and circumstances of this failure are not clear to me.  Does anyone have any further information?

https://twitter.com/GeotechTips/status/1250045392047095808?s=20

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Perhaps the most interesting aspect of this video is the manner in which the toe of the punches up, deforming the pavement of the road.  The motorcyclist is rather lucky, aided by a well-timed swerve and bail out.  The motorbike itself appears to be buried at the end of the video.

Viewed after the event, the deposit of this landslide might give one the impression that it had been quite a benign process.  The video shows the violence of even quite small landslides.

The other video is the collapse of the Dehdasht – Pataveh tunnel portal in Iran, which occurred on 9 April 2020. This video has been posted to Youtube.  The video shows a tunnel portal undergo a large-scale rock mass failure:-

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Others will be able to comment on the construction method at this site, but it seems surprising to me that a situation can arise in which these two large rock columns can be undermined without additional support being put in place.  It would seem to have been at high risk of a toppling failure due to the very clear vertical fractures  that permitted the detachment of the two large rock blocks:-

The collapse of Dehdasht – Pataveh tunnel portal in Iran. Stills from a video posted to Youtube.

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According to the text that accompanies the video, “the Dehdasht – Pataveh tunnel which is under construction of the IRGC Khatam-al Anbia Construction collapsed on April 9. The project was started back in 1994 and was supposed to be completed in 2004.”

I have no way to verify this information.