ULTRA-LOW FRICTION TIME-CHANGE MODEL AND ENERGY CONVERSION OF DEEP COAL-ROCK INTERFACE

The ultra-low friction impact ground pressure of deep coal rock is essentially a time-varying process in which a large amount of coal rock mass is instable and sliding along the coal-rock interface, during which the friction and friction coefficient of the coal-rock interface change with time, and at the same time, the energy conversion characteristics of releasing energy from the impact kinetic energy of the coal-rock interfacial with the frictional force of the coal-rock interface. In order to quantitatively describe the energy conversion law of coal rock interface, the dimensional analysis method is introduced, and the elastic coefficient, damping coefficient and pending coefficient of coal rock are experimentally determined, and the expression of the friction coefficient of deep coal rock interface is given. Taking Shenyang Hongyang Three Mines as the research object, through the combination of experimental research and engineering practice, a new index of impact kinetic energy conversion rate is defined, the reliability of the built model is verified, and the law of coal-rock interface friction work to coal-rock impact kinetic energy conversion is quantitatively described. The results show that the interfacial friction coefficient of deep coal rocks decreases linearly with the increase of the amplitude of the impact load, and increases linearly with the increase of the frequency of the impact load. When the impact load amplitude is 5000 N and the impact load frequency is 500 Hz, the ultra-low friction effect occurs when the friction force of deep coal rock interface decreases by 97% and the reduction rate is 38.9 kN/ms ~ 41.38 kN/ms. For the first time, the ultra-low friction effect is quantitatively described in terms of friction reduction amplitude and reduction rate. Combined with the experimental and engineering actual analysis, it is found that the average experimental result of the energy consumption ratio is 0.441, and the calculation result of the "11.11" impact ground pressure of Hongyang Three Mines is 0.488, which is relatively close, which further proves the rationality of the proposed model.