不同粒度弱胶结砂岩声发射信号源与其临界破坏前兆信息判识

Acoustic emission signal sources and critical failure precursors of weakly consolidated sandstone with different grain sizes

  • 摘要: 研究弱胶结砂岩声发射信号参数特征及参数之间的关联性,可以区分不同粒度弱胶结砂岩破坏过程的声发射信号源,是建立不同粒度弱胶结砂岩临界破坏判据的基础。通过对单轴压缩下不同粒度弱胶结砂岩的破坏全过程进行声发射试验,得到了弱胶结砂岩破坏全过程中的应力与AE特征参数随时间演化规律,分析了AE振铃计数与绝对能量、幅值和持续时间参数之间的分布特征,获得了不同粒度弱胶结砂岩声发射信号源特征,并基于AE峰值频率的演化特征分析,给出了弱胶结砂岩临界破坏前兆信息识别方法。研究表明,随着弱胶结砂岩粒度的减小,其峰值强度增加,岩样破坏时表现出的脆性破坏更加明显,AE振铃计数的峰值呈现数量级增加,能量集聚效应更加明显,岩样的自蓄能能力更强,且产生更高的AE幅值及更长的AE持续时间。弱胶结细粒砂岩在线弹性阶段初期最先出现更低频段(10~20 kHz);弱胶结粗粒砂岩在塑性变形阶段AE峰频出现更高频(275~285 kHz),且AE峰频由2个主频段演化为5个;弱胶结中粒砂岩在达到应力峰值前,两个主频段(40~50,145~155 kHz)累积计数最大;AE峰频的更高频、更低频及主频累积计数值等变化特征可以作为鉴别不同粒度弱胶结砂岩单轴压缩破坏过程中声发射信号源的判识依据。岩样进入塑性变形阶段时,AE峰值频率表现为由初期的2个主频演化为4个或5个频段,频段增加特征亦可作为不同粒度弱胶结砂岩破坏前兆信息判识的依据。

     

    Abstract: The characteristic parameter data of acoustic emission signals of weakly cemented sandstones and their correlation characteristics were studied,which can be used to distinguish the acoustic emission signal sources of different granularity weakly cemented sandstones during the failure process.It is also the basis for establishing critical failure criteria for weakly cemented sandstones with different grain sizes.Acoustic emission (AE) tests were carried out on the whole process of damaging sandstones with different particle sizes under uniaxial compression.The evolution of stress and AE characteristic parameters during the whole process of rock specimen failure was obtained.The distribution relationship between the AE ringing count and the parameters of absolute energy,amplitude,and duration is established to identify the characteristics of acoustic emission signal sources of weakly cemented sandstone with different grain sizes.At the same time,based on the analysis of the evolution characteristics of AE peak frequency,a method for identifying the precursor information of critical failure of weakly cemented sandstone was given.The results show that with the decrease of the particle size of the weakly cemented sandstone,the brittle failure of the rock sample is more obvious,the peak of the AE ringing count in-creases by an order of magnitude,the energy accumulation effect is more obvious,the self-accumulation ability of the rock sample is stronger,and a higher AE amplitude and a longer AE duration are produced.The weakly ce-mented fine-grained sandstone first appears in the lower frequency band (10-20 kHz) in the initial elastic stage,the weakly cemented coarse-grained sandstone appears higher frequency (275-285 kHz) in the AE peak frequency during the plastic deformation stage,and the AE peak frequency composed of two main frequency bands has evolved into five frequency bands.The weakly cemented medium sandstone has the largest cumulative count of the two main frequency bands (40-50,145-155 kHz) before reaching the stress peak.The higher frequency,lower frequency and main frequency cumulative count value can be a different identification basis for the acoustic emission signal source of particle size weakly cemented sandstone.When the rock sample enters the plastic deformation stage,the AE peak frequency appears to evolve from the initial two main frequencies to four or five frequency bands,and the frequency band increase phenomenon can be used as the precursor information for the weak cemented sandstone destruction.

     

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