煤层注水预防冲击地压的机理探讨

DISCUSSION ON MECHANISM OF ROCK BURST PREVENTION BY WATER INFUSION

煤层注水是防治冲击地压的一种主要措施。通过水的物理化学等作用,煤体的结构和物理力学性质将发生改变。据试验测定,当含水率增加到3％时,煤样单轴抗压强度下降32％;煤样强度下降与煤样浸水时间的关系式为σ_c=34.82×e^(-0.0771),说明湿润时间对煤的强度有不容忽视的影响。浸水软化后的煤样出现明显塑化,C,φ值分别降低了10％和70％,煤的冲击倾向显著减弱。有限元模拟的结果表明,注水后支承压力高峰位置由距煤壁9m向煤体深部移至14m,应力集中系数由3.68降至2.74。注水软化显著改善了煤层开采过程中的能量释放的均匀性和稳定性;这是煤层注水防治冲击地压的机理。从现场实测和对比试验结果也能得出同样的结论。

In-seam water infusion is a major measure for prevention of rock burst. The structure, physical and mechanical properties of coal solid will change after physical and chemical reaction with water. Based on measurement, when moisture content increases by 3%, the uniaxial compressive strength of coal sample reduces by 32%. The relation between reduction of coal sample strength and immersion time of coal sample is σ_c=34.82e^(-0.077t), This shows that the effect of wetting time on coal strength can not be neglected. After softening by water immersion, coal samples become evidently plastic, the values of C and φ reduce by 10% or 70% respectively. The proneness of coal burst also reduces remarkably. The results of finite element simulation have shown that the position of peak abutment pressure after water infusion moves from 9 m in front of the coalface to 14 m. The stress concentration coefficient reduces from 3.68 to 2.74. Water infusion and softening make energy release uniformly and steadily in mining process. This is the mechanism of in-seam water infusion for prevention of rock bursts. We can get the same conclusion from site measurement results and from comparison with test results.