不同孔隙率及孔隙水压条件下无烟煤蠕变特性研究

Study on Creep Characteristics of Anthracite Under Different Porosities and Pore Water Pressures

长期浸泡在采空水中的残采煤柱,会发生蠕变失稳。为研究孔隙率及孔隙水压对煤柱蠕变特性的影响,以山西沁水煤田3#无烟煤为研究对象,以三维CT扫描技术为手段,对无烟煤试样进行孔隙尺度分类,并对不同孔隙率煤样进行分级加载单轴蠕变试验,得出不同孔隙率无烟煤蠕变本构模型,嵌入FLAC3D数值模拟软件中,模拟不同孔隙率及孔隙水压下无烟煤的蠕变规律。结果表明:(1)不同孔隙率无烟煤试样均经历瞬时变形、衰减蠕变、稳定蠕变和加速蠕变4个阶段;(2)随着加载水平的增加,试样瞬时应变逐渐减小,进入稳定蠕变阶段所经历的时间缩短;(3)孔隙率一定时,随着孔隙水压的增加,煤样轴向应变增大;(4)孔隙水压相同时,孔隙率越小,试样变形量越少;(5)随着孔隙率及孔隙水压的增加,煤样进入加速蠕变阶段的时间越短。

The residual pillar immersed in goaf water for a long time will produce creep instability.In order to study the effects of porosities and pore water pressure on the creep characteristics of coal pillars,3# anthracite in Qinshui coalfield of Shanxi Province was taken as the research object.The pore-scale classification of anthracite samples was carried out by threedimensional CT scanning technique,and the creep constitutive model of anthracite with different porosity was obtained by the uniaxial creep tests on coal samples with different porosities.The creep law of anthracite under different porosity and pore water pressure was simulated by the numerical simulation software FLAC3D.The results are concluded as follows.Firstly,the samples with different porosity undergo four stages of transient deformation,decay creep,stable creep and accelerated creep.Secondly,with the increase of loading level,the instantaneous strain of the samples decreases gradually,and the time entering the stable creep stage is shortened.Thirdly,the axial strain of the samples increases with the increase of pore water pressure when the porosity is constant.Fourthly,when the pore water pressure is fixed,the smaller the porosity,the smaller the deformation.At last,with the increase of porosity and pore water pressure,the time of coal samples entering the accelerated creep stage is shorter.