水对含孔煤体蠕变声发射特性影响的试验研究

Experimental study on effect of water on creep acoustic emission characteristics of coal containing pores

水是影响煤体稳定的主要因素。为了全面分析水对钻孔周围煤岩体蠕变声发射特性的影响,通过室内制取含水率0、4%、8%以及饱和含水4种含水状态的单孔试样,开展不同含水率下的分级加载蠕变声发射试验,得到不同含水率下钻孔周围煤岩蠕变声发射规律。试验结果表明:(1)含水率的改变影响钻孔孔周煤岩体的蠕变力学性质,蠕变瞬时应变与稳态应变随含水率的增加呈指数上升,其中饱和含水试样应变增幅更加明显,其瞬时应变及稳态应变最大增幅达到44.5%和28.6%。(2)含水率影响蠕变过程中累计振铃计数及轴向应变的大小,轴向应变随着含水率的增加而增加,累计振铃计数随着轴向应变的增加呈线性上升,且含水率越大,累计振铃计数增加幅度越大,不同应力水平下,含水率4%、8%及饱和含水试样的累计振铃计数增减幅度基本维持在43%、53%和74%。(3)声发射振铃率在每一级蠕变阶段都会有增长—减小—稳定的趋势,随着含水率增加声发射活跃程度明显降低,并且蠕变曲线相对于声发射数据在时间上会出现一个滞后效应。研究为瓦斯抽采、钻孔护孔及声发射检测方面提供了指导。

Water is the main factor affecting the stability of coal and rock.In order to comprehensively analyze the influence of water on the creep acoustic emission characteristics of coal and rock around the borehole,single-hole samples with water contents of 0,4%,8% and saturated water content were prepared in the laboratory in this paper.The grading loading creep acoustic emission test was carried out to obtain the creep acoustic emission law of coal and rock around the borehole under different water content.According to the creep acoustic emission test under graded loading under different water contents,the creep acoustic emission law of coal and rock around the borehole under different water content was obtained.The test results show that:(1) The change of water content affects the creep mechanical properties of the surrounding rock mass,and the creep transient strain and steady-state strain increase exponentially with the increase of water content,and the strain increase of saturated water sample is greater.Obviously,the maximum increase of instantaneous strain and steady-state strain reaches 44.5% and 28.6%.(2) The water content affects the cumulative ringing count and axial strain during the creep process.The axial strain increases with the increase of water content,and the cumulative ringing count increases linearly with the increase of axial strain.The higher the rate,the greater the increase of the cumulative ringing count.Under different stress levels,the increase and decrease of the accumulative ringing count of the samples with water contents of 4%,8% and saturated water content basically maintained at 43%,53% and 74%.(3) The acoustic emission ringing rate has a trend of increasing-decreasing-stabilizing in each stage of creep.As the water content increases,the acoustic emission activity decreases significantly,and the creep curve is temporally relative to the acoustic emission data.There will be a hysteresis effect.The research provides guidance for gas drainage,borehole protection and acoustic emission detection.