The key stratum is not easy to cave, but once it is caved, there will be a sudden collapse of a rather thickstratum.
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。
2
Under stratum condition of thick soil layer, we can study it as random medium and use probability integral method to estimate surface movement.
在厚松散层地层结构条件下，可将其视为随机介质，采用概率积分法预计地表移动变形。
3
The vital problems to be solved in Shendong mine are the dynamic pressure damage of thin rock strata roof under thick sandy soil soft stratum and the loss of water and soil under mining.