本文選題：次聲信號 + 不同破壞模式��； 參考：《江西理工大學》2017年碩士論文

【摘要】：巖石失穩(wěn)破壞過程是一種能量不斷累積到一定程度而后突然釋放的過程,是一種累積效應。因此開展監(jiān)測巖體在能量累積過程中伴隨的物理現(xiàn)象并究其特征,獲取巖體失穩(wěn)過程中起到破壞前兆特征作用的信息,是進行巖體失穩(wěn)可監(jiān)測預警的研究方向。研究表明次聲信號具有傳播距離遠、能量衰減小的特點,克服周圍環(huán)境次聲噪音干擾,通過研究巖石加載過程中低頻聲發(fā)射信號特征,建立次聲信號與巖體失穩(wěn)之間關(guān)聯(lián)性,可獲得巖石失穩(wěn)破壞重要的前兆信息。本文以室內(nèi)試驗為基礎,進行了單軸壓縮試驗、成45°斜剪試驗、巴西劈裂試驗以及單軸循環(huán)加卸載試驗四種試驗,在進行各種巖石力學試驗的同時進行次聲信號采集。對采集的次聲信號進行小波分解與重構(gòu),獲得頻率為0~16 Hz的次聲時域信號,通過對次聲時域信號特征分析以及波形特性分析,得到以下主要結(jié)論:(1)通過單軸壓縮試驗與斜剪試驗結(jié)果分析發(fā)現(xiàn)巖石在變剪切破壞形式下中能產(chǎn)生突出次聲波信號,且在最終巖石試件在應力峰值點次聲信號強度達到最大。(2)劈裂破壞過程中次聲信號與實驗室本底信號區(qū)別不大,次聲信號不明顯,劈裂試驗次聲現(xiàn)象不明顯存在2種可能:1、劈裂時產(chǎn)生的次聲信號強度較小于實驗室環(huán)境噪聲次聲信號強度;2、劈裂試驗破壞時大部分聲信號為高頻信號,數(shù)據(jù)處理時已經(jīng)過濾掉而次聲信號過少。(3)試驗過程中次聲傳感器與加載巖石試樣間隔了約2.5 m的空間直線距離,明顯區(qū)別于聲發(fā)射監(jiān)測需要傳感器與巖石試樣緊密耦合的方式,說明巖石變形破壞產(chǎn)生的次聲波信號能通過一定距離空氣傳播,不用通過傳感器直接接觸巖體而能進行巖體穩(wěn)定性監(jiān)測,這使得次聲波的現(xiàn)場監(jiān)測更加方便。(4)通過對巖石單軸循環(huán)加卸載試驗各級加卸載次聲信號事件累計振鈴數(shù)統(tǒng)計可以看出,在第五級加卸載階段(約為應力峰值80%~90%左右區(qū)段)次聲信號事件累計振鈴計數(shù)在卸載階段明顯多于該級加載階段,出現(xiàn)異常。(5)巖石在加載破壞過程中產(chǎn)生的次聲信號主要頻帶能量分布在1~4 Hz,在應力初始階段1~4 Hz頻帶能量占比達50%左右,隨著加載應力的不斷增大,這一頻帶能量占比越來越大,峰值點可達85%以上。(6)分形維數(shù)在應力初始階段處于較低水平,隨著加載應力的不斷增加,分形維數(shù)開始出現(xiàn)劇烈波動,起伏較初始階段大,當分形維數(shù)出現(xiàn)驟降后,預示著巖石即將發(fā)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 擄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.
【學位授予單位】：江西理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TD315

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