Study on Destabilization Damage Precursors of Sandstone under Dry and Wet Cycles Based on Critical Slowing Theory
The fluctuation of groundwater level and periodic changes in reservoir water cause the rock mass to be fre-quently exposed to alternating wet-dry cycles,leading to potential instability issues in engineering rock masses.To investigate the instability resulting from such wet-dry cycling,uniaxial compression tests on sandstone were conducted under varying num-bers of wet-dry cycles,with real-time monitoring of acoustic and thermal signals both internally and externally within the sam-ples.Based on critical slowing-down theory,the critical slowing-down characteristics of acoustic and thermal signals,as well as precursor signs of instability and failure,were explored.The study reveals that as the number of wet-dry cycles increases,the sandstone experiences significant strength degradation,accompanied by enhanced post-peak ductility.The acoustic emission en-ergy and infrared counts within the samples exhibit distinct stage characteristics,with the onset of acoustic emission energy ac-tivity tending to advance with each additional wet-dry cycle.Notably,both the variance and autocorrelation coefficient of acous-tic emission energy and infrared counts manifest clear precursor information prior to sample instability and failure.In terms of variance,the precursor response time for infrared counts precedes that of acoustic emission,accounting for approximately 86%of the total time.Conversely,for autocorrelation coefficient,the precursor response time for acoustic emission energy precedes infrared counts,accounting for around 78%of the time.The variance of infrared counts shows a more pronounced and distinct anomaly preceding failure,compared to the autocorrelation coefficient,occurring during the plastic deformation phase when mi-crocracks coalesce and new cracks initiate.Therefore,the variance of infrared counts is proposed as the primary indicator for i-dentifying sandstone instability and failure,while the autocorrelation coefficient of acoustic emission serves as a secondary crite-rion.This research contributes to elucidating the precursor signals of sandstone instability and failure under wet-dry cycling,providing a theoretical basis for early warning systems against sudden rock failures in mining engineering.
sandstonedry-wet cycleacoustic emissionthermal infraredcritical slowing theory
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