Collapses in Mengshan area are caused by the weightless rock mass falling down rapidly due to the interaction of gravity and weathering factor of freeze-and-thaw action and raining action in the locate of the developing joints.

• 崩塌是在陡崖或坡度陡峻的斜坡地带因岩体节理裂隙发育，受冻融、雨水等风化作用和重力作用，造成岩体失稳快速下落的现象。