【摘要】：巖石脆性破壞是個漸進發(fā)生的過程,損傷強度是巖石破壞過程中重要的應(yīng)力門檻值,是巖石壓縮過程中不同破壞階段的分界點,也是裂紋非穩(wěn)定擴展的起點。為充分了解紅砂巖單軸加載下?lián)p傷強度損傷與聲發(fā)射特征,本文通過對紅砂巖進行室內(nèi)聲發(fā)射試驗,分析了聲發(fā)射累計振鈴計數(shù)與主頻變化規(guī)律,探討了聲發(fā)射法、裂紋體積應(yīng)變模型法、損傷統(tǒng)計本構(gòu)模型法與耗散能法表征紅砂巖損傷的適用性與差異性;結(jié)合紅砂巖損傷強度,研究紅砂巖損傷強度聲發(fā)射變化規(guī)律與損傷特征。綜合以上研究內(nèi)容,主要研究結(jié)論如下:(1)單軸加載下,基于裂紋應(yīng)變模型法確定的紅砂巖損傷強度與峰值強度的比為0.69~0.85。(2)損傷強度前巖石內(nèi)部裂紋壓密后又重新擴展,聲發(fā)射累計振鈴計數(shù)穩(wěn)定增加,損傷強度以后巖石內(nèi)部裂紋非穩(wěn)定擴展,聲發(fā)射累計振鈴計數(shù)急劇增加,聲發(fā)射累計振鈴計數(shù)急劇增長點在損傷強度以后,聲發(fā)射急劇增長點比峰值應(yīng)力的值與損傷強度比峰值應(yīng)力的值差為0.15~0.3。(3)在初始壓密階段和彈性階段,聲發(fā)射主頻主要集中在100~350 kHz,損傷強度點后,有大量0~50 kHz和400~500 kHz的聲發(fā)射信號出現(xiàn),聲發(fā)射主頻帶變寬,主頻范圍變?yōu)?~500 kHz;損傷強度以前,巖石內(nèi)部裂紋壓密與重新擴展,0~160 kHz的低頻聲發(fā)射信號一般不超過加載全程的20%;300~500 kHz的高頻聲發(fā)射信號一般不超過16%。(4)聲發(fā)射法、裂紋體積應(yīng)變模型法、損傷統(tǒng)計本構(gòu)模型法與耗散能法均能較好的表征紅砂巖單軸加載損傷規(guī)律,四種損傷變量表征的損傷具有高度一致性,損傷強度處,基于聲發(fā)射法表征的損傷變量值不超過0.2,基于裂紋體積應(yīng)變模型法表征的損傷變量值不超過0.35,基于損傷統(tǒng)計本構(gòu)模型法表征的損傷變量值小于0.18,基于耗散能法表征的損傷變量值不超過0.15,基于裂紋體積應(yīng)變模型法表征的損傷變量要其他3種方法表征的損傷變量。損傷強度前,巖石損傷較小,損傷強度以后損傷急劇增大導(dǎo)致巖石失穩(wěn)破壞,巖石損傷主要集中在裂紋非穩(wěn)定擴展階段。(5)能量耗散主要集中在損傷強度以后的塑性屈服階段,巖石內(nèi)部的裂紋擴展貫通,巖石損傷急劇增大。巖石耗散的能量一部分被聲發(fā)射接收,聲發(fā)射急劇增多;另一部分能量用于裂紋的急劇擴展與貫通,最終導(dǎo)致巖石失穩(wěn)破壞。
[Abstract]:Brittle failure of rock is a gradual process. The damage strength is an important stress threshold in the process of rock failure, the boundary point of different failure stages in the process of rock compression, and the starting point of unstable crack propagation. In order to fully understand the damage intensity damage and acoustic emission (AE) characteristics of red sandstone under uniaxial loading, this paper analyzes the accumulative ringing count and main frequency variation of red sandstone by laboratory acoustic emission test, and discusses the acoustic emission method. Crack volume strain model method, damage statistical constitutive model method and dissipative energy method are used to characterize the applicability and difference of red sandstone damage, and combined with the damage intensity of red sandstone, the changes of damage intensity and damage characteristics of red sandstone are studied. The main conclusions are as follows: (1) under uniaxial loading, the ratio of damage strength to peak strength of red sandstone determined by the method of crack strain model is 0.69 ~ 0.85. The accumulative ringing count of acoustic emission increases steadily, the internal crack of rock expands unsteadily after the damage intensity, the accumulative ring count of acoustic emission increases sharply, and the sharp growth point of accumulative ring count of acoustic emission increases after the damage intensity. The difference between the value of peak stress and the ratio of damage intensity to peak stress of sharp growth point of acoustic emission is 0.15 ~ 0.30.3.In the initial compaction stage and elastic stage, the main frequency of acoustic emission is mainly concentrated after the damage intensity point of 100 ~ 350 kHz,. A large number of acoustic emission signals of 0 ~ 50 kHz and 400 ~ 500 kHz appeared, the main frequency band of acoustic emission became wider, and the main frequency range changed to 0 ~ 500 kHz; damage intensity. The low frequency acoustic emission (LOAE) signals of the internal crack compaction and repropagation of a rock are generally not more than that of the full loading range of 20, 300 and 500 kHz. (4) the acoustic emission method, the crack volume strain model method, are generally not more than 16 parts. The damage statistical constitutive model method and dissipative energy method can well characterize the damage law of red sandstone under uniaxial loading. The damage variable value based on acoustic emission method is not more than 0.2, the damage variable value based on crack volume strain model method is not more than 0.35, the damage variable value based on damage statistical constitutive model method is less than 0.18, and the damage variable value based on dissipative energy method table. The damage variable value is not more than 0.15. The damage variable based on the crack volumetric strain model is the damage variable characterized by the other three methods. Before the damage intensity, the rock damage is small, and the damage increases sharply after the damage strength, which leads to the rock instability failure, and the rock damage is mainly concentrated in the stage of the crack unsteady growth. (5) the energy dissipation is mainly concentrated in the plastic yield stage after the damage strength. Crack propagation through the rock leads to a sharp increase in rock damage. Some of the dissipated energy of rock is received by acoustic emission, and the other part of energy is used for crack propagation and penetration, which leads to rock instability and failure.
【學(xué)位授予單位】：江西理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TD315

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本文編號：2201941