穿煤隧道层面性质对岩柱安全厚度的影响研究

Influence Study of Layer Properties of Tunnel Through Coal Seam on the Safety Thickness of Rock Column

煤与瓦斯突出是穿煤隧道工程施工过程中最常见的灾害之一,其发生受到煤层结构、揭煤方式及围岩结构面性质的影响。以重庆旗杆山隧道为例,利用ABAQUS有限元软件,对不同煤层倾角下的隧道围岩应力和位移变化进行了模拟分析,并推导岩柱安全厚度计算方法,讨论层面软硬程度、结合程度及倾角对岩柱安全厚度的影响。研究表明:煤层倾角小于90°时,随着煤层倾角增大,围岩最大等效应力减小,最大水平位移增大,煤层倾角为90°时最易发生煤与瓦斯突出。煤层倾角为90°条件下,岩柱安全厚度约为2~3 m;岩柱安全厚度随层面软硬程度降低和结合程度减弱而增大,随层面倾角增大而近线性减小;层面结构面由Ⅰ类变化为Ⅴ类时,岩柱安全厚度增大约1.4至1.8倍;层面倾角由30°增大到75°时,岩柱安全厚度减小约76.4%至79.9%。

Coal and gas outbursts are among the most common hazards during the construction of tunneling through coal,and the coal seam structure,the coal uncovering method,and the nature of the surrounding rock structure surface influence their occurrence.Taking Chongqing Qiganshan Tunnel as an example,ABAQUS software was used to simulate and analyze the stress and displacement changes of the tunnel surrounding rock under different coal seam dip angles.A calculation method for the safety thickness of the rock column was deduced,and the impact of the hardness degree,binding degree and dip angle of the structural plane on the safety thickness of rock column were discussed.The study shows that:When the dip angle of the coal seam is less than 90°,with the increase of the dip angle of the coal seam,the maximum equivalent force of the surrounding rock decrease,the maximum horizontal displacement increase,and coal and gas outburst are most likely to occur when the dip angle of the coal seam is 90°.The safe thickness of rock column is about 2~3 m under the condition that the dip angle of coal seam is 90°.The safety thickness of rock column increases with the decrease of softness and hardness of structural surface and the weakening of bonding,and decreases nearly linearly with the increase of structural surface inclination;the safety thickness of rock column increases about 1.4 to 1.8 times when the structural plane changes from type I to type V;the safety thickness of rock column decreases about 76.4%to 79.9%when the dip angle of structural surface increases from 30°to 75°.