超临界CO_2作用下煤体膨胀变形规律试验研究

为解决采用应变片对超临界CO_2作用下煤体膨胀变形进行点测量时,试验结果离散性大、超临界CO_2作用导致应变片易脱离破损等问题,自主研发了具有施加热流力载荷功能的膨胀体积应变测量装置,对不同温度、压力的超临界CO_2作用下,煤体膨胀体积变形规律进行研究。结果表明:煤体膨胀体积应变随超临界CO_2作用时间增加呈现先增大后趋于稳定的变化规律;当孔隙压力不变时,膨胀体积应变随超临界温度的升高而增加,温度越高,达到稳定膨胀变形所需时间越长;当温度不变时,随着超临界孔隙压力增加,膨胀体积应变也随之增大,但达到稳定膨胀变形所需时间随孔隙压力的升高呈先增加后减少的趋势;超临界CO_2作用下,煤体体积应变随温度和孔隙压力均呈"S型"Logistic函数规律变化;膨胀体积应变对超临界温度和孔隙压力的变化率具有分区性,其变化率大小排序依次为:近临界区跨临界区高临界区。

Experimental Study of Coal Swelling Deformation under Supercritical Carbon Dioxide Action

In experiment of coal swelling deformation under supercritical carbon dioxide action,strain gauge is a common device for point measurement.But obtained results are often scattered,meanwhile,strain gauge is easy to break out in experiment.To solve above problems,a volume expansion strain measurement device with heat flow loading function was developed by authors.Using this device,coal swelling volume deformation under supercritical carbon dioxide action can be experimentally studied at different temperature and under different pressure.Results show that the variation pattern of coal swelling volumetric strain is increasing first and then tending to stable with the increase of supercritical carbon dioxide action time.When the pore pressure is constant,the swelling volumetric strain increases with the increase of critical temperature,the higher the temperature is,the longer the required time to achieve stable expansion deformation.When the temperature is constant,swelling volumetric strain increases with the increase of supercritical pore pressure,but with the increase of pore pressure,the required time to reach steady expansion deformation is increasing first then decreasing.Under the action of supercritical carbon dioxide,the coal volumetric strain varies with the temperature and pore pressure and presents "S" type Logistic function pattern.The variation rate of swelling volumetric strain due to supercritical temperature and pore pressure has zoning characteristics,the order from low to high is:near critical area＞ cross critical area＞high critical area.