The caves used to be much larger but rockfalls over time have progressively reduced their extent. There are reports that the ill-fated group lit a fire in the cave. I must stress that this is unconfirmed. Sometimes however falls like this are triggered by campfires lit in the cave, which induce thermal stresses in the ceiling that trigger the collapse. I am not sure if this is the case here - it could well be that the group were just very unlucky indeed - but fires in caves with low ceilings can be a quite significant hazard. Sadly, it is very unlikely that the group would have known about that particular danger.
Showing posts with label cave. Show all posts
Showing posts with label cave. Show all posts
Monday, April 6, 2009
Cave rockfall in Shropshire, England
The British newspapers are reporting that overnight a rockfall occurred in Hermitage Cave near to Bridgnorth in Shropshire, England. This is news because at the time there was a group of teenagers camping in the cave. Sadly, one of them was killed and another was badly injured. These caves are old dwellings cut into the Bridgnorth Sandstone (see image below from here):
The caves used to be much larger but rockfalls over time have progressively reduced their extent. There are reports that the ill-fated group lit a fire in the cave. I must stress that this is unconfirmed. Sometimes however falls like this are triggered by campfires lit in the cave, which induce thermal stresses in the ceiling that trigger the collapse. I am not sure if this is the case here - it could well be that the group were just very unlucky indeed - but fires in caves with low ceilings can be a quite significant hazard. Sadly, it is very unlikely that the group would have known about that particular danger.
The caves used to be much larger but rockfalls over time have progressively reduced their extent. There are reports that the ill-fated group lit a fire in the cave. I must stress that this is unconfirmed. Sometimes however falls like this are triggered by campfires lit in the cave, which induce thermal stresses in the ceiling that trigger the collapse. I am not sure if this is the case here - it could well be that the group were just very unlucky indeed - but fires in caves with low ceilings can be a quite significant hazard. Sadly, it is very unlikely that the group would have known about that particular danger.
Thursday, March 5, 2009
Karst landslide in China
Xinhua is reporting a landslide in Jinjiling Hill in Guilin, Guangxi yesterday that buried several houses and killed four people. Whilst in global terms the event was not huge, the images that Xinhua have published are quite interesting:
Xinhua describes the event thus: "...several hundred tonnes of rocks and dirt gushed down from the mountain at about 9:20 p.m. Wednesday. Four workers in charge of a cave-digging project in the hill, the project contractor and his wife were in the houses when the accident took place, the city's public security bureau said. Jiang Mingyi, head of the city's geological environment monitoring station, said ongoing rain over the past few days triggered the landslide and the local karst-landform is prone to mountain collapse in the rainy season."
It would be easy to ascribe this collapse to the caving digging work that was going on at the toe of the slope. However, the failure appears to have occurred on an unfavourably orientated joint high up on the slope. The initial collapse was possibly quite small, but the failure has accrued debris on the way down to create quite a large failure. Thus, the interpretation that the failure was rainfall-induced looks spot on.
Of course, what is not clear is the degree to which the work at the toe of the slope disturbed the joints upslope. If blasting was being used this is of course quite possible.
Xinhua describes the event thus: "...several hundred tonnes of rocks and dirt gushed down from the mountain at about 9:20 p.m. Wednesday. Four workers in charge of a cave-digging project in the hill, the project contractor and his wife were in the houses when the accident took place, the city's public security bureau said. Jiang Mingyi, head of the city's geological environment monitoring station, said ongoing rain over the past few days triggered the landslide and the local karst-landform is prone to mountain collapse in the rainy season."
It would be easy to ascribe this collapse to the caving digging work that was going on at the toe of the slope. However, the failure appears to have occurred on an unfavourably orientated joint high up on the slope. The initial collapse was possibly quite small, but the failure has accrued debris on the way down to create quite a large failure. Thus, the interpretation that the failure was rainfall-induced looks spot on.
Of course, what is not clear is the degree to which the work at the toe of the slope disturbed the joints upslope. If blasting was being used this is of course quite possible.
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