ULTRA-LOW FRICTION TIME-CHANGE MODEL AND ENERGY CONVERSION OF DEEP COAL-ROCK INTERFACE
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摘要: 深部煤岩超低摩擦型冲击地压实质是巨量煤岩体沿煤岩界面发生失稳滑动的时变过程, 期间煤岩界面摩擦力和摩擦系数随时间变化, 同时伴随煤岩界面摩擦力做功向煤岩冲击动能释放能量转化特征. 为定量描述煤岩界面能量转化规律, 引入量纲分析法, 实验测定了煤岩弹性系数、阻尼系数和待定系数, 给出了深部煤岩界面摩擦系数表达式. 以沈阳红阳三矿为研究对象, 通过实验研究和工程实际相结合, 定义了冲击动能转化率新指标, 验证了所建模型可靠性, 定量描述了煤岩界面摩擦力做功向煤岩冲击动能转化规律. 研究结果表明: 深部煤岩界面摩擦系数随冲击载荷幅值增大而线性降低, 随冲击载荷频率增大而线性增加. 深部煤岩界面摩擦力的降幅和降低速率变化急剧, 当冲击载荷幅值为5000 N、冲击载荷频率为500 Hz时, 深部煤岩界面摩擦力降幅为97%、降低速率为38.9 kN/ms ~ 41.38 kN/ms时发生超低摩擦效应. 首次从摩擦力降低幅值和降低速率定量表征超低摩擦效应. 结合实验和工程实际分析发现, 能耗比实验结果均值为0.441, 红阳三矿“11.11”冲击地压计算结果为0.488, 两者较为接近, 进一步证明所建模型合理性.Abstract: 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.
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表 1 参数量纲
Table 1. Dimension of parameters
Parameter Symbol Dimension load time-varying P MLT−2 static load time t0 T elasticity coefficient k MT−2 damping coefficient c MT−1 gravity acceleration g LT−2 coefficient of friction µ 1 表 2 煤样单轴压缩实验结果
Table 2. Uniaxial compression test results of coal
Coal number Elastic modulus/GPa compressive strength
$ {\sigma _c} $/MPaElasticity coefficient k/(N·m−1) 1# 1.00 11.74 8.6 × 105 2# 1.11 13.02 9.8 × 105 3# 1.10 15.05 9.8 × 105 4# 1.29 14.77 1.3 × 106 5# 1.09 13.94 1.5 × 106 average 1.12 13.70 1.1 × 106 表 3 砂岩单轴压缩试验结果
Table 3. Uniaxial compression test results of sandstone
Sandstone number Elastic modulus/GPa compressive strength $ {\sigma _c} $/MPa Elasticity coefficient k/(N·m−1) 1# 5.05 42.11 2.6 × 106 2# 4.56 44.02 2.4 × 106 3# 4.69 47.78 2.3 × 106 4# 3.62 37.44 2.9 × 106 5# 4.96 38.78 4.9 × 106 average 4.58 42.03 3.0 × 106 表 4 实验测定摩擦系数数据
Table 4. Experimental determination of friction coefficient data
Static load time t0/s Counterweight mass/kg 3 5 10 15 20 100 0.517 0.521 0.522 0.527 0.526 1000 0.527 0.527 0.530 0.532 0.540 10000 0.533 0.534 0.538 0.537 0.544 表 5 不同静载时间和冲击应力下能量转化数据
Table 5. Energy conversion data under different static load times and impact stresses
The experiment
numberStatic load
time t0/msHorizontal impact
stress/MPaFriction
energy Wf/JImpact kinetic
energy Ek/JEnergy consumption
ratio nAverage Energy
consumption ratio1 100 0.5 4.2937 1.9150 0.446 0.441 2 1.0 4.5112 1.9759 0.438 3 1.5 5.0100 2.1643 0.432 4 2.0 4.9253 2.2016 0.447 5 1000 0.5 4.0670 1.8098 0.445 6 1.0 4.3856 1.8902 0.431 7 1.5 4.7182 2.0194 0.428 8 2.0 4.6601 2.0458 0.439 9 10000 0.5 3.8656 1.7511 0.453 10 1.0 4.1000 1.8245 0.445 11 1.5 4.4092 1.9268 0.437 12 2.0 4.6911 2.1063 0.449 -
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