基于RA/AF的高温后砂岩破裂特征识别研究

Fracture feature recognition of sandstone after high temperature based on RA/AF

开展岩石高温损伤破裂信息识别研究对地热开发和煤炭地下气化等具有重要的指导意义。通过不同高温处理后砂岩在破坏过程中声发射参数RA(上升时间/振幅)和AF(平均频率)值变化,研究高温后砂岩内部不同类型裂纹的发展演化规律。结果表明:砂岩在整个加载过程中以拉张裂纹为主,当加载应力超过峰值应力的80%后,剪切裂纹所占比例迅速增大,可将此作为砂岩发生破坏的前兆;当加热温度超过600℃时,剪切裂纹所占比例上升,超过800℃,剪切裂纹所占比例迅速下降,600℃和800℃可作为砂岩损伤突变的阈值温度;高温后位错塞积现象增多,砂岩塑性特征增强,拉张裂纹所占比例增大。研究成果将对高温作用后岩石破裂失稳前兆信息的识别提供重要的理论基础。

It is of great significance to carry out the research on rock high temperature damage information identification for geothermal development and underground coal gasification.Based on the changes of acoustic emission parameters RA and AF in the failure process of sandstone after different high temperature treatments,the development and evolution law of different types of cracks in sandstone after high temperature treatment are studied.The results show that tensile cracks are dominant in the whole loading process of sandstone.When the loading stress exceeds 80%of the peak stress,the proportion of shear cracks increases rapidly,which can be regarded as the precursor of sandstone failure.When the heating temperature exceeds 600℃,the proportion of shear cracks increases.When temperature exceeds 800℃,the proportion of shear cracks decreases rapidly.Therefore,600℃and 800℃can be regarded as the threshold temperature of sandstone damage mutation.After high temperature treatment,the dislocation pileup phenomenon increases,the plastic characteristics of sandstone strengthen,and the proportion of tensile cracks increases.The research results will provide an important theoretical basis for the identification of precursor information of rock fracture and instability after high temperature treatent.