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

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 dry-wet 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.