The origin of the hazard is the disordered mining of coal pits along a river, and geological and environmental factors are the necessary conditions of the hazard.
沿河小煤窑的无序开采是这种地质灾害产生的根源，而地质及环境因素是灾害产生的必要条件。
2
There are strict regulations in top-coal caving mining with hazard of coal and gas outburst. The main reason is the problem of safety.
煤与瓦斯突出危险煤层的放顶煤开采有严格的法规限制，限制主要是从安全上考虑的。
3
Collapse of mined-out area is an environmental geological hazard of the coal mining area.