不同冷却方式对热损伤砂岩力学与声学特征影响

Effects of different cooling methods on mechanical and acoustic characteristics of thermally damaged sandstone

本文选取地球岩石圈中典型的砂岩作为研究对象,通过开展高温作用后的砂岩在自然冷却与遇水冷却两种条件下的声波透射试验、岩石孔渗测量。分析砂岩在不同温度处理、不同冷却方式下的声发射特征、孔渗参数、弹性模量,结合岩石在常温下各参数进行对比分析。研究结果表明:(1)随热处理温度的增加,砂岩P波速度不断下降,质量损失率不断上升,且两个参数出现明显变化的阈值温度皆在400~600℃;(2)经不同的冷却方式处理下,动弹性模量都随热处理温度的升高而减小,以400℃为拐点,可以将整个曲线分为平缓下降、急剧减小两个阶段,且试样在水冷条件下的动弹性模量下降幅度更大,数值均低于自然冷却时的试样;(3)经热处理后试样的孔隙度、渗透率随温度的升高出现先慢后快的上升趋势,突变的阈值温度均在400~600℃,400℃处理后,试样的渗透率达低于400℃处理后试样的200~600倍。

This paper selects typical sandstone in the earth's lithosphere as the research object,through carrying out the acoustic transmission experiment and porosity measurement of the sandstone after the high temperature work under the two conditions of natural cooling and water cooling.Analyzing the acoustic emission characteristics,porosity and permeability parameters,and elastic modulus of sandstone under different temperature treatments and different cooling ways,contrasting with the various parameters of the rock at room temperature.The results show that,(1)As the heat treatment temperature increases,the P wave velocity of sandstone continues to decrease,and the quality loss rate keeps rising,we can see the threshold temperature at which the two parameters change significantly is between 400~600℃.(2)Handled by different cooling methods,the dynamic modulus of elasticity decreases with the increase of heat treatment temperature,taking 400℃as the inflection point,the whole curve can be divided into two stages,gentle decrease and sharp decrease,and the dynamic elastic modulus of the sample under water cooling has a greater decrease,especially the values are lower than those samples under natural cooling.(3)After heating treatment,the porosity and permeability of the sample appear to increase slowly and then quickly with the increase of temperature,the threshold temperature of sudden change is between 400~600℃,after 400℃treatment,the permeability of the sample is 200~600 times lower than that after 400℃treatment.