不同加载路径下岩石破坏次声信号特征研究

发布时间：2018-05-11 20:37

本文选题：次声信号 + 不同破坏模式　；参考：《江西理工大学》2017年硕士论文

【摘要】：岩石失稳破坏过程是一种能量不断累积到一定程度而后突然释放的过程,是一种累积效应。因此开展监测岩体在能量累积过程中伴随的物理现象并究其特征,获取岩体失稳过程中起到破坏前兆特征作用的信息,是进行岩体失稳可监测预警的研究方向。研究表明次声信号具有传播距离远、能量衰减小的特点,克服周围环境次声噪音干扰,通过研究岩石加载过程中低频声发射信号特征,建立次声信号与岩体失稳之间关联性,可获得岩石失稳破坏重要的前兆信息。本文以室内试验为基础,进行了单轴压缩试验、成45°斜剪试验、巴西劈裂试验以及单轴循环加卸载试验四种试验,在进行各种岩石力学试验的同时进行次声信号采集。对采集的次声信号进行小波分解与重构,获得频率为0~16 Hz的次声时域信号,通过对次声时域信号特征分析以及波形特性分析,得到以下主要结论:(1)通过单轴压缩试验与斜剪试验结果分析发现岩石在变剪切破坏形式下中能产生突出次声波信号,且在最终岩石试件在应力峰值点次声信号强度达到最大。(2)劈裂破坏过程中次声信号与实验室本底信号区别不大,次声信号不明显,劈裂试验次声现象不明显存在2种可能:1、劈裂时产生的次声信号强度较小于实验室环境噪声次声信号强度;2、劈裂试验破坏时大部分声信号为高频信号,数据处理时已经过滤掉而次声信号过少。(3)试验过程中次声传感器与加载岩石试样间隔了约2.5 m的空间直线距离,明显区别于声发射监测需要传感器与岩石试样紧密耦合的方式,说明岩石变形破坏产生的次声波信号能通过一定距离空气传播,不用通过传感器直接接触岩体而能进行岩体稳定性监测,这使得次声波的现场监测更加方便。(4)通过对岩石单轴循环加卸载试验各级加卸载次声信号事件累计振铃数统计可以看出,在第五级加卸载阶段(约为应力峰值80%~90%左右区段)次声信号事件累计振铃计数在卸载阶段明显多于该级加载阶段,出现异常。(5)岩石在加载破坏过程中产生的次声信号主要频带能量分布在1~4 Hz,在应力初始阶段1~4 Hz频带能量占比达50%左右,随着加载应力的不断增大,这一频带能量占比越来越大,峰值点可达85%以上。(6)分形维数在应力初始阶段处于较低水平,随着加载应力的不断增加,分形维数开始出现剧烈波动,起伏较初始阶段大,当分形维数出现骤降后,预示着岩石即将发生破裂。
[Abstract]:The failure process of rock instability is a process of energy accumulation to a certain extent and then released suddenly, which is a cumulative effect. Therefore, it is the research direction of monitoring rock mass instability to monitor the accompanying physical phenomena in the process of energy accumulation and study the characteristics of rock mass instability, and to obtain the information that plays a leading role in the process of rock mass instability. The study shows that infrasound signal has the characteristics of long propagation distance and low energy attenuation. It overcomes the interference of ambient infrasound noise and establishes the correlation between infrasound signal and rock mass instability by studying the characteristics of low frequency acoustic emission signal during rock loading. Important precursor information of rock instability and failure can be obtained. On the basis of laboratory tests, uniaxial compression tests were carried out, including 45 掳oblique shear test, Brazilian splitting test and uniaxial cyclic loading and unloading test. Infrasound signals were collected at the same time of various rock mechanics tests. The infrasound signal is decomposed and reconstructed by wavelet transform, and the infrasonic time domain signal with frequency of 0 ~ 16 Hz is obtained. The characteristics of infrasound time domain signal and waveform characteristic are analyzed. The main conclusions are as follows: (1) through uniaxial compression test and oblique shear test, it is found that rock can produce prominent infrasonic wave signal in the form of variable shear failure. Moreover, the infrasound signal of the final rock specimen has little difference from the laboratory background signal in the process of the maximum intensity of infrasound signal at the stress peak, and the infrasound signal is not obvious. The infrasound phenomenon of splitting test is not obvious. The infrasound signal produced by splitting is smaller than that of laboratory noise infrasound signal. Most of the infrasound signals in splitting test are high frequency signals. During data processing, infrasound signals are filtered and infrasound signals are too few.) during the test, the distance between infrasound sensor and loaded rock specimen is about 2.5 m, which is obviously different from the mode of tight coupling between sensor and rock sample in acoustic emission monitoring. It shows that the infrasonic wave signal produced by rock deformation and failure can be transmitted through air at a certain distance, and the rock mass stability monitoring can be carried out without direct contact with rock mass by sensor. This makes the field monitoring of infrasonic waves more convenient. (4) through the statistics of the cumulative ringing number of infrasound signal events in each stage of the loading and unloading test of rock under uniaxial cyclic loading and unloading, it can be seen that In the fifth stage of loading and unloading (about 80% of the stress peak value), the accumulative ringing count of infrasound signal events in the unloading stage is obviously more than that in the stage of loading. The main frequency band energy of infrasound signal produced in the process of loading and failure of rock is 1 ~ 4 Hz, and the frequency band energy of 1 ~ 4 Hz is about 50% of Prida in the initial stage of stress. With the increasing of loading stress, the frequency band energy of infrasound signal is about 50% of Prida. The ratio of energy in this frequency band is increasing, and the peak value can reach more than 85%. 6) the fractal dimension is at a lower level in the initial stage of stress. With the increasing of the loading stress, the fractal dimension begins to fluctuate violently, and the fluctuation is larger than that in the initial stage. When the fractal dimension drops suddenly, it indicates that the rock is about to break.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD315

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