7.The hardness and thickness of coal seam play a great role in the vertical distribution of stress in coal and the occurrence of rock bunt under the condition of hard roof and hard floor.

• 研究表明,煤层围岩岩体结构控制了煤层瓦斯的赋存,岩体结构可用岩层效应厚度影响系数来表示,应用这一参数研究煤层瓦斯赋存比用煤层顶板岩性及含砂率更科学。