盐水干湿循环作用下红砂岩损伤及蠕变声发射试验研究

Sandstone Damage and Creep Acoustic Emission under Salt Water Dry-wet Cycle

为研究水化学溶液作用下红砂岩的损伤劣化机制,在Na2SO4溶液和NaOH溶液两种盐溶液环境下进行了干湿循环试验和蠕变声发射试验。结果表明:红砂岩的初始损伤随着干湿循环次数的增加而逐渐累积,砂岩在酸性Na2SO4溶液中的损伤劣化程度大于在NaOH溶液中的损伤劣化程度;随着干湿循环次数的增大,砂岩的初始损伤越来越严重,蠕变声发射信号逐渐从高频高幅值向低频低幅值转变,声发射累计事件数逐渐减小;相同干湿循环次数下,Na2SO4溶液中砂岩的声发射累计事件数低于NaOH溶液中砂岩的声发射累计事件数;声发射b值呈“降低-动态稳定-突降-增大”四个变化阶段,突降出现在加速蠕变阶段前后,可作为砂岩即将发生蠕变失稳破坏的前兆;声发射b值随着干湿循环次数的增加而逐渐增大,水化学损伤软化现象越严重,蠕变过程中小尺度的破坏占比越大。

To study the damage and deterioration mechanism of red sandstone under the action of aqueous chemical solution,a dry-wet cycle test and creep acoustic emission test were carried out in Na2SO4 solution and NaOH solution.The results showed that the damage of red sandstone gradually accumulates with the increase of dry-wet cycle times,and the damage deterioration degree of sandstone in acid Na2SO4 solution is greater than that in NaOH solution.With the increase of dry-wet cycles,the softening damage of sandstone is becoming increasingly severe,the creep acoustic emission signal gradually changes from"high frequency and high amplitude"to"low frequency and low amplitude",and the cumulative number of acoustic emission events gradually decreases.Under the same drywet cycle times,the cumulative number of acoustic emission events of sandstone in Na2SO4 solution is lower than that in NaOH solution.The acoustic emission b value shows four stages of"decrease-dynamic stability-sudden drop-increase".The sudden drop occurs before and after the accelerated creep stage,which can be used as a precursor of creep instability failure of sandstone.The b value of acoustic emission gradually increases with the increase of dry-wet cycles.The more serious the hydrochemical damage softening phenomenon is,the greater the proportion of small-scale damage in the creep process.