Yan Jiaju, Li Zhuxi, Xia Dong, Bai Yuxin, Shao Guoliang
College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China.
Hebei Province Mining Industry Development with Safe Technology Priority Laboratory, North China University of Science and Technology, Tangshan 063210, China.
Materials (Basel). 2024 Jun 27;17(13):3147. doi: 10.3390/ma17133147.
The frequency domain characteristics of acoustic emission can reflect issues such as rock structure and stress conditions that are difficult to analyze in time domain parameters. Studying the influence of immersion time on the mechanical properties and acoustic emission frequency domain characteristics of muddy mineral rocks is of great significance for comprehensively analyzing rock changes under water-rock coupling conditions. In this study, uniaxial compression tests and acoustic emission tests were conducted on sandstones containing montmorillonite under dry, saturated, and different immersion time conditions, with a focus on analyzing the effect of immersion time on the dominant frequency of rock acoustic emission. The results indicated that immersion time had varying degrees of influence on compressive strength, the distribution characteristics of dominant acoustic emission frequencies, the frequency range of dominant frequencies, and precursor information of instability failure for sandstones. After initial saturation, the strength of the rock sample decreased from 53.52 MPa in the dry state to 49.51 MPa, and it stabilized after 30 days of immersion. Both dry and initially saturated rock samples exhibited three dominant frequency bands. After different immersion days, a dominant frequency band appeared between 95 kHz and 110 kHz. After 5 days of immersion, the dominant frequency band near 0 kHz gradually disappeared. After 60 days of immersion, the dominant frequency band between 35 kHz and 40 kHz gradually disappeared, and with increasing immersion time, the dominant frequency of the acoustic emission signals increased. During the loading process of dry rock samples, the dominant frequency of acoustic emission signals was mainly concentrated between 0 kHz and 310 kHz, while after saturation, the dominant frequencies were all below 180 kHz. The most significant feature before the rupture of dry rock samples was the frequent occurrence of high frequencies and sudden changes in dominant frequencies. Before rupture, the characteristics of precursor events for initially saturated and immersed samples for 5, 10, and 30 days were the appearance and rapid increase in sudden changes in dominant frequencies, as well as an enlargement of the frequency range of dominant frequencies. After 60 days of immersion, the precursor characteristics of rock sample rupture gradually disappeared, and sudden changes in dominant frequencies frequently occurred at various stages of sample loading, making it difficult to accurately predict the rupture of specimens based on these sudden changes.
声发射的频域特征能够反映诸如岩石结构和应力条件等在时域参数中难以分析的问题。研究浸泡时间对泥质矿物岩石力学性能和声发射频域特征的影响，对于全面分析水 - 岩耦合条件下的岩石变化具有重要意义。在本研究中，对含蒙脱石的砂岩在干燥、饱和及不同浸泡时间条件下进行了单轴压缩试验和声发射试验，重点分析浸泡时间对岩石声发射主频的影响。结果表明，浸泡时间对砂岩的抗压强度、声发射主频分布特征、主频频率范围以及失稳破坏前兆信息均有不同程度的影响。初始饱和后，岩石样品强度从干燥状态下的53.52MPa降至49.51MPa，浸泡30天后强度趋于稳定。干燥和初始饱和的岩石样品均呈现三个主频带。浸泡不同天数后，在95kHz至110kHz之间出现一个主频带。浸泡5天后，0kHz附近的主频带逐渐消失。浸泡60天后，35kHz至40kHz之间的主频带逐渐消失，且随着浸泡时间增加，声发射信号的主频升高。干燥岩石样品加载过程中，声发射信号的主频主要集中在0kHz至310kHz之间，而饱和后，主频均低于180kHz。干燥岩石样品破裂前最显著的特征是高频频繁出现且主频突变。破裂前，初始饱和及浸泡5天、10天和30天样品的前兆事件特征是主频突变出现并迅速增加，以及主频频率范围扩大。浸泡60天后，岩石样品破裂的前兆特征逐渐消失，主频突变在样品加载的各个阶段频繁出现，难以基于这些突变准确预测试件的破裂。
