Study And Application On Improving The Stability Of Gas Drainage Drilling By High Strength Inner Support Pipe

Soft and high-gas coal is widely distributed in China.Drilling is the main measure to prevent gas disaster.Due to the low hardness of soft coal,the drilling is easy to deform,collapse and block the gas flow channel.It is great impact on the gas extraction efficiency.Based on the theoretical analysis,basic mechanics test,numerical simulation and field engineering test,this paper takes the high-strength inner support pipe to improve the stability of the gas drainage technology.Based on the factors affecting the stability of drilling,the division of axial and radial "three zones" around the borehole is discussed.The calculation of stress and displacement under drilling is studied,and the main stress in drilling is analyzed.In this paper,the mechanical properties of the hole in the borehole are analyzed,and the basic mechanical properties of the material are as follows:(1)PPR pipe is more resistant to compression and deformation,but the tensile strength torsional shear capacity is poor;PE pipe in the basic mechanics experiment performance is moderate;PVC pipe is relatively poor.(2)The radial support capacity of the new inner support pipe is more than 3 times higher than that of the conventional pipe.The vertical displacement of the top of the borehole is reduced by the support of the FLAC3 Dnumerical simulation software,and the vertical stress distribution of the surrounding rock is smaller than that of the plastic zone of the surrounding rock,and the support pipe support the effect is more significant.Through the different supporting methods and types of screen support site engineering test,that:(1)Hole mesh screen diameter eight millimeter,density 6 per meter or 8 per meter.(2)Within the support of the screen support and ordinary screen support,gas pumping pure and bare hole contrast were improved 1.05 times,0.58 times,and the support of the screen support pumping time marked a significant decline.