Research Of The Ultra-low Friction Effect Of Rock Mass Under Confining Pressure And Impact Load

The deep underground mining is deeper,the surrounding pressure is greater,and the shear failure form of the coal rock is clearer.The transformation of the rock mass to the block medium is more prominent,and the friction "disappear" is remarkable.The equilibrium constraint.is destroyed,and the friction sliding and instability is caused,finally the rock explosion.rock burst and other dynamic disasters are induced,which pose a serious threat to the safety of the mine.Therefore,it is of great theoretical significance and practical application value for the research on the mechanism of ultra-low friction of rock mass.In this paper,the methods of numerical simulation and experimental research arecarried out to study the ultra-low friction effect of block rock mass under the influence of bi-directional impact load and confining pressure.Horizontal displacement response curve of block under different confining pressure and different impact load is obtained and the horizontal displacement difference curve and the acceleration difference curveof two rock monitoring points in the same contact interface are also obtained.The effect to the ultra-low friction effect of block rock mass is analyzed.When the bi-directional impact load and the confining pressure are applied to the granite model system,the vibration frequency of the vertical acceleration attenuation curve increases at the same vibration time.There are multiple extremes in a short period of time,and the curve becomes more irregular.Especially in the free vibration stage,The larger the load pressure,the vibration time is longer,and the extreme value of the curve is frequent,and the low friction effect is more likely to occur.When the bi-directional impact load and the confining pressure are applied to the coal rock composite block system,the horizontal acceleration difference curve is slowed down by the forced vibration stage,the vibrational extreme value is more,and the vibration frequency is fast.The larger the confining load,the slower the curve will decay in the forced vibration stage,and the stronger the irregularity.This phenomenon shows that the coal rock mass is susceptible to low friction during forced vibration phase.The greater the vertical impact load,the greater the displacement of the horizontal displacement curve,Therefore,the vertical impact load leads to the ultra-low friction of the coal rock mass.