水岩作用下煤岩组合体力学特性损伤劣化机制

Timeliness of damage and deterioration of mechanical properties of coal-rock combined body under water-rock interaction

大水矿山和富水环境条件下的煤岩体以及井下留设的隔水煤岩柱均会受到地下水的侵蚀影响,煤岩体在水岩作用下的力学特性与损伤将直接影响其稳定和安全。基于此,对细砂岩-煤(FC)、粗砂岩-煤(GC)、细砂岩-煤-粗砂岩(FCG)3种煤岩组合体开展不同浸水时间下的单轴压缩试验,研究水岩作用下煤岩组合体力学特性演化规律和声发射损伤特征,分析煤岩组合体水岩作用下的劣化机制。结果表明:(1)随浸水时间的增加,组合体含水率逐渐增大,但增幅减小;相同浸水时间下GC组合体的含水率最高,FC组合体含水率最低;组合体浸水40 d时,已基本达到饱水状态。(2)随着浸水时间的增加,组合体的抗压强度逐渐减小,抗压强度总劣化度和阶段劣化度表现出一定的时间效应和非均匀性;随着浸水时间的增加,劣化效应逐渐减弱。相同浸水时间下,FC组合体的抗压强度最大,GC组合体的抗压强度最小。(3)随着浸水时间的增加,3种组合体的弹性模量均出现不同程度的降低,弹性模量总劣化度不断增大;浸水前期,弹性模量的劣化效应较为明显,浸水后期,劣化效应较弱。(4)随着浸水时间的增加,组合体的声发射累积能量和累积数出现不同程度的减少,试样的储能能力和应变能释放能力显著降低,试样的塑性增强。(5)构建了基于浸水时间的组合体损伤模型,由模型可知,随着浸水时间增加,水对组合体的损伤也不断增加,但增幅逐渐变小。(6)详细分析了水岩作用下煤岩组合体的劣化机制,水对煤岩试样的物理、化学、力学作用导致试样内部微观结构的变化,进而导致抗压强度、弹性模量等力学特性的劣化。水岩作用对煤岩组合体的劣化效应是从微观到宏观的损伤累积过程。

The coal and rock mass under water-rich coal mine environment and the underground water-prevention coal and rock pillar will be affected by groundwater erosion,and the mechanical properties and damage of coal and rock mass under the action of water and rock will directly affect its stability and safety.Based on this,the uniaxial compression tests of three kinds of coal-rock combined bodies including fine sandstone-coal(FC),coarse sandstone-coal(GC)and fine sandstone-coal-coarse sandstone(FCG)were carried out under different immersion times.The deterioration law of mechanical properties and acoustic emission damage characteristics of coal-rock combined body under water-rock interaction were studied,and the deterioration mechanism of coal-rock combined body was analyzed in detail.The results show that(1)With the increase of immersion time,the water content of the composite increases gradually,but the increase rate decreases.At the same immersion time,the moisture content of GC composite is the highest,while that of FC composite is the lowest.When the combination is immersed in water for 40 days,it basically reaches the state of being saturated.(2)With the increase of immersion time,the compressive strength of the composite decreases gradually,and the total deterioration degree and stage deterioration degree of compressive strength show a certain time effect and non-uniformity.With the increase of immersion time,the deterioration effect decreases gradually.Under the same immersion time,the compressive strength of FC composite is the highest,while that of GC composite is the lowest.(3)With the increase of immersion time,the elastic modulus of three combinations decrease in varying degrees,and the total deterioration degree of elastic modulus increases.In the early stage of immersion,the deterioration effect of elastic modulus is obvious,but in the later stage,the deterioration effect is weak.(4)With the increase of immersion time,the AE cumulative energy and cumulative number of the composite decrease in varying degrees,the energy storage capacity and strain energy release capacity of the sample decrease significantly,and the plasticity of the sample increases.(5)The damage model of the combination based on the immersion time is constructed.It is known from the model that with the increase of immersion time,the damage of the combination caused by water increases,but the increase rate decreases gradually.(6)The deterioration mechanism of coal-rock combined body under the action of water and rock is analyzed in detail.The physical,chemical and mechanical effects of water on the coal-rock samples lead to the change of internal microstructure of coal-rock samples,which leads to the deterioration of mechanical properties such as compressive strength and elastic modulus.The deterioration effect of water-rock interaction on coal-rock combined body is a damage accumulation process from microscopic to macroscopic.