For impervious layer, the anti-inrushing stability of the pit is analyzed from the plastic damage of soil, but for semipervious layer, the anti-inrushing stability of the pit is analyzed from the seepage damage of soil.

• 坑底为不透水层土时，应从土体发生突涌塑性破坏的角度进行分析；坑底为弱透水层土时，应从土体发生突涌渗透破坏的角度进行分析。