浸水次数对煤样裂隙发育损伤的实验研究

Experimental research of effect of water intrusion times on crack propagation in coal

由于地下水对隔水煤柱和地下水库边界的反复浸水损伤,研究反复浸水对煤样的裂隙损伤作用有助于解决中国西部干旱区半干旱区矿区井下储水以及含水层煤柱留设问题。通过自制浸水装置制取干燥,浸水1次,2次,3次,4次的煤样共5组,分别进行单轴压缩声发射实验。研究表明,煤样的峰值应力、弹性模量随着煤样浸水次数的增加而呈现不同程度的减小,但峰值应变随着浸水次数的增加而变大。刚度应力曲线结合声发射累计计数曲线能阐明裂隙发育的各个阶段,随着反复浸水次数增加,煤样裂隙的闭合应力阈值,裂隙初始发育阈值和裂隙损伤阈值均线性减小,但3个阈值占峰值强度的比值不随着浸水次数改变而变化,其比值分别为15.52%,31.04%和67.81%。实验结果对矿区地下水库建立和隔水煤岩体留设以及探究煤样裂隙发育规律具有指导意义。

Underground water has repeated intrusion on waterproof coal pillars and on underground reservoir boundaries. Therefore,researching the damaging effect of water intrusion times on crack propagation in coal gives meaningful advice to cope with problems,such as setting the width of water proof coal pillars and storing underground water in arid region of the West China. In this paper,coal samples were wetted by self-made humidifier and then were grouped into dry coal samples,coal samples under once water intrusion,twice water intrusion,third water intrusion and forth water intrusion. By acoustic emission testing,this research found the peak stress and elastic modulus decreased with the growth of water intrusion times but peak strain increased because of the rising water intrusion times. The stiffness-stress curve and accumulative AE counts combined with overall strain-stress curve could evaluate all phases of crack propagation. With the growing times of water intrusion,the stress thresholds of crack closure,crack initiation and crack damage declined linearly. Nevertheless,the percentage of three stress thresholds over peak stress did not vary with the change of water-intrusion times,with 15.52%,31.04% and 67.81% respectively. The experimental results can partly help set the width of waterproof coal pillars and of underground reservoir boundaries.