The key stratum is not easy to cave, but once it is caved, there will be a sudden collapse of a rather thick stratum.

关键层较难崩落，但在崩落时具有突发性，会产生较大厚度岩层的突然垮塌。

youdao

On September 5, 1944, when making charcoal in Ansai County, northern Shaanxi, he was killed by the sudden collapse of a kiln.

1944年九月五日在陕北安塞县山中烧炭，因炭窑崩塌而牺牲。

youdao

Experts on site suspected that the sudden collapse of an underground karst cave created by eroded limestone caused the sinkhole, but the investigation is ongoing.

勘察了现场的砖家怀疑石灰岩被腐蚀，导致地下的喀斯特溶洞突然坍塌，从而形成了天坑，但调查还在进行中。

youdao

This man said at about five o'clock in the morning, he heard the dam collapse and all of sudden the water rushed towards the houses.

VOA: standard.2009.03.27

Fire crews said the main concern was the uncertainty of the sheer face, with sudden collapse a possibility.

BBC: Firefighters at the scene

Community leaders are at a loss to explain the sudden collapse of harmony.

ECONOMIST: Indonesia: Terror in the spice islands | The

The subsequent sudden collapse of Enron was unanticipated by the Compensation Committee during the negotiations with Mr. Lay in August 2001.

FORBES: Estate of Enron CEO Kenneth Lay Wins in Tax Court