不同中間主應(yīng)力下應(yīng)變型巖爆聲發(fā)射特征研究
發(fā)布時(shí)間：2018-09-01 15:19
【摘要】：巖爆是深部開挖過程中一種常見的地質(zhì)災(zāi)害。隨著水利水電、交通、礦山開采等工程向地下深部開拓,巖爆的強(qiáng)度及發(fā)生頻率呈上升趨勢(shì),嚴(yán)重威脅工程安全。國(guó)內(nèi)外學(xué)者圍繞巖爆的機(jī)理及預(yù)測(cè)問題開展了大量研究,但巖爆的孕育發(fā)生較為復(fù)雜,巖爆的發(fā)生機(jī)制仍不十分清楚,巖爆預(yù)測(cè)與防控已成為地下巖體工程建設(shè)中亟待解決的技術(shù)難題。因此,深入開展巖爆的基礎(chǔ)試驗(yàn)研究具有重要的學(xué)術(shù)意義及工程價(jià)值。本文借助改進(jìn)的巖爆真三軸試驗(yàn)系統(tǒng),開展不同中間主應(yīng)力下的應(yīng)變巖爆試驗(yàn),利用聲發(fā)射監(jiān)測(cè)系統(tǒng)對(duì)巖爆試驗(yàn)過程進(jìn)行監(jiān)測(cè),分析了不同中間主應(yīng)力下花崗巖應(yīng)變型巖爆的聲發(fā)射特征。并獲得以下結(jié)論:(1)中間主應(yīng)力對(duì)巖爆聲發(fā)射撞擊數(shù)及其分形維數(shù)Dt的變化特征具有顯著影響。低中間主應(yīng)力條件下,各組試驗(yàn)彈塑性階段分形維數(shù)Dt小于0.3,撞擊數(shù)在300左右。隨著中間主應(yīng)力在較低水平增加,“平靜期”持續(xù)時(shí)間存在先增大后減小的變化趨勢(shì)。最終破壞階段各組試驗(yàn)撞擊數(shù)有所增加,分形維數(shù)Dt大于0.3。高中間主應(yīng)力條件下,彈塑性階段撞擊數(shù)分形維數(shù)Dt大于0.3,撞擊數(shù)在500以上。塑性變形階段“平靜期”持續(xù)時(shí)間顯著增長(zhǎng)。在最終破壞階段撞擊數(shù)分形維數(shù)Dt小于0.3,撞擊時(shí)降低至300以下。(2)中間主應(yīng)力對(duì)巖爆聲發(fā)射信號(hào)能量累積具有顯著影響。低中間主應(yīng)力下,聲發(fā)射信號(hào)絕對(duì)能量累積較少,隨著中間主應(yīng)力在較小范圍內(nèi)的增加,絕對(duì)能量累積呈現(xiàn)先增大后減小的變化趨勢(shì)。高中間主應(yīng)力下,聲發(fā)射絕對(duì)能量累積明顯增多,并隨著中間主應(yīng)力的增大呈現(xiàn)遞增。需要特別指出的是,不同中間主應(yīng)力下,聲發(fā)射的絕對(duì)能量變化規(guī)律與巖爆發(fā)生烈度變化規(guī)律基本上是一致,這說明了聲發(fā)射絕對(duì)能量可以間接反映巖爆發(fā)生烈度。(3)中間主應(yīng)力對(duì)巖爆聲發(fā)射信號(hào)波形參數(shù)具有重要影響。不同中間主應(yīng)力下聲發(fā)射信號(hào)波形具有不同的參數(shù)特征。低中間主應(yīng)力下,聲發(fā)射波形的上升時(shí)間較長(zhǎng)、持續(xù)時(shí)間較短、幅度較小;高中間主應(yīng)力下,聲發(fā)射波形的上升時(shí)間較短、持續(xù)時(shí)間較長(zhǎng)、幅度較大。(4)從聲發(fā)射的角度對(duì)不同中間主應(yīng)力下應(yīng)變型巖爆的發(fā)生機(jī)制進(jìn)行了分析,發(fā)現(xiàn)了不同中間主應(yīng)力對(duì)應(yīng)變型巖爆的破壞具有不同影響。低中間主應(yīng)力(10-90MPa)作用下,隨著中間主應(yīng)力的增大,其對(duì)聲發(fā)射活動(dòng)的抑制作用逐漸增強(qiáng),試件內(nèi)部破壞活動(dòng)減弱,試件強(qiáng)度逐漸增強(qiáng)(90MPa時(shí),試件強(qiáng)度最大)。聲發(fā)射總撞擊數(shù)、絕對(duì)能量累積隨著中間主應(yīng)力在較低水平內(nèi)的增加呈現(xiàn)出先增大后減小的變化趨勢(shì),相應(yīng)的巖爆烈度呈現(xiàn)出先增大后減小的變化趨勢(shì)。高中間主應(yīng)力(100-llOMPa)作用下,隨著中間主應(yīng)力的增大,其對(duì)聲發(fā)射活動(dòng)的抑制作用轉(zhuǎn)變?yōu)榇龠M(jìn)作用,試件內(nèi)部破壞活動(dòng)增強(qiáng),試件強(qiáng)度逐漸降低,聲發(fā)射總撞擊數(shù)及絕對(duì)能量累積顯著上升,相應(yīng)的巖爆烈度顯著增強(qiáng)。(5)分析了巖爆前夕的聲發(fā)射撞擊數(shù)及分形維數(shù)Dt,發(fā)現(xiàn)聲發(fā)射“平靜期”前的撞擊數(shù)相對(duì)較低(通常在300左右),撞擊數(shù)分形維數(shù)Dt小于0.3,巖體可能發(fā)生受低中間主應(yīng)力作用的巖爆。此種巖爆,巖爆坑較淺,破壞程度及范圍較小,巖爆彈射速度快,彈射塊體具有較大的殺傷力。若聲發(fā)射“平靜期”前的撞擊數(shù)相對(duì)較高(通常在500以上),撞擊數(shù)分形維數(shù)Dt值大于0.3,巖體可能發(fā)生受高中間主應(yīng)力作用的巖爆,此種巖爆彈射破壞速度極快,巖爆坑較深,破壞程度及范圍較大,容易造成隧洞內(nèi)大面積掩埋,在實(shí)際工程中具有較大危害。
[Abstract]:Rockburst is a common geological hazard during deep excavation. With the development of water conservancy and Hydropower projects, traffic, mining and other projects to the deep underground, the intensity and frequency of rock burst are increasing, which seriously threatens the safety of engineering. The mechanism of rock burst is still unclear, and the prediction and control of rock burst have become a technical problem to be solved urgently in the construction of underground rock mass projects. Therefore, it is of great academic significance and engineering value to carry out the basic test research of rock burst in depth. The acoustic emission (AE) characteristics of strain-type rock burst in granite under different intermediate principal stresses are analyzed. The following conclusions are obtained: (1) The intermediate principal stress has a significant effect on the AE impact number and its fractal dimension Dt of rock burst. Under the stress condition, the fractal dimension Dt of each group is less than 0.3, and the impact number is about 300. With the increase of intermediate principal stress at a lower level, the duration of "quiet period" increases first and then decreases. The impact fractal dimension Dt of elastic-plastic stage is greater than 0.3 and the impact number is more than 500. The duration of "quiet period" in plastic deformation stage increases significantly. Under stress, the absolute energy accumulation of AE signal is less, and with the increase of intermediate principal stress in a smaller range, the absolute energy accumulation increases first and then decreases. The change of absolute energy of AE under inter-principal stress is basically the same as that of the intensity of rock burst, which indicates that the absolute energy of AE can indirectly reflect the intensity of rock burst. (3) The intermediate principal stress has an important influence on the waveform parameters of AE signals. The rise time of AE waveform is longer, the duration time is shorter and the amplitude is smaller under the low intermediate principal stress. The rise time of AE waveform is shorter, the duration time is longer and the amplitude is larger under the high intermediate principal stress. (4) The occurrence mechanism of strain-type rock burst under different intermediate principal stress is divided from the angle of AE. It is found that different intermediate principal stresses have different effects on the failure of strained rock burst. Under the action of low intermediate principal stress (10-90 MPa), with the increase of intermediate principal stress, the inhibiting effect on AE activity is gradually strengthened, the internal failure activity is weakened, and the strength of specimen is gradually strengthened (the maximum strength is at 90 MPa). The absolute energy accumulation increases first and then decreases with the increase of intermediate principal stress at a lower level, and the corresponding rock burst intensity increases first and then decreases. The total impact number and absolute energy accumulation of acoustic emission (AE) increased significantly, and the corresponding rock burst intensity increased significantly. (5) The AE impact number and fractal dimension Dt before rockburst were analyzed. It was found that the impact number before AE "quiet period" was relatively low (usually around 300). Rockburst may occur in rock mass under the action of low intermediate principal stress when the fractal dimension Dt is less than 0.3. This kind of rock burst has shallow rock burst pit, small damage degree and scope, rapid rockburst ejection speed and large lethality of the projectile block. If the impact number before the quiet period of acoustic emission is relatively high (usually more than 500), the fractal dimension Dt of the impact number is relatively high. When the value is greater than 0.3, rock burst may occur under the action of high and middle principal stress. The rock burst is destroyed very fast, the rock burst pit is deep, the damage degree and scope are large, and it is easy to cause large area burial in the tunnel, which is harmful to the actual project.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU45
本文編號(hào)：2217590
[Abstract]:Rockburst is a common geological hazard during deep excavation. With the development of water conservancy and Hydropower projects, traffic, mining and other projects to the deep underground, the intensity and frequency of rock burst are increasing, which seriously threatens the safety of engineering. The mechanism of rock burst is still unclear, and the prediction and control of rock burst have become a technical problem to be solved urgently in the construction of underground rock mass projects. Therefore, it is of great academic significance and engineering value to carry out the basic test research of rock burst in depth. The acoustic emission (AE) characteristics of strain-type rock burst in granite under different intermediate principal stresses are analyzed. The following conclusions are obtained: (1) The intermediate principal stress has a significant effect on the AE impact number and its fractal dimension Dt of rock burst. Under the stress condition, the fractal dimension Dt of each group is less than 0.3, and the impact number is about 300. With the increase of intermediate principal stress at a lower level, the duration of "quiet period" increases first and then decreases. The impact fractal dimension Dt of elastic-plastic stage is greater than 0.3 and the impact number is more than 500. The duration of "quiet period" in plastic deformation stage increases significantly. Under stress, the absolute energy accumulation of AE signal is less, and with the increase of intermediate principal stress in a smaller range, the absolute energy accumulation increases first and then decreases. The change of absolute energy of AE under inter-principal stress is basically the same as that of the intensity of rock burst, which indicates that the absolute energy of AE can indirectly reflect the intensity of rock burst. (3) The intermediate principal stress has an important influence on the waveform parameters of AE signals. The rise time of AE waveform is longer, the duration time is shorter and the amplitude is smaller under the low intermediate principal stress. The rise time of AE waveform is shorter, the duration time is longer and the amplitude is larger under the high intermediate principal stress. (4) The occurrence mechanism of strain-type rock burst under different intermediate principal stress is divided from the angle of AE. It is found that different intermediate principal stresses have different effects on the failure of strained rock burst. Under the action of low intermediate principal stress (10-90 MPa), with the increase of intermediate principal stress, the inhibiting effect on AE activity is gradually strengthened, the internal failure activity is weakened, and the strength of specimen is gradually strengthened (the maximum strength is at 90 MPa). The absolute energy accumulation increases first and then decreases with the increase of intermediate principal stress at a lower level, and the corresponding rock burst intensity increases first and then decreases. The total impact number and absolute energy accumulation of acoustic emission (AE) increased significantly, and the corresponding rock burst intensity increased significantly. (5) The AE impact number and fractal dimension Dt before rockburst were analyzed. It was found that the impact number before AE "quiet period" was relatively low (usually around 300). Rockburst may occur in rock mass under the action of low intermediate principal stress when the fractal dimension Dt is less than 0.3. This kind of rock burst has shallow rock burst pit, small damage degree and scope, rapid rockburst ejection speed and large lethality of the projectile block. If the impact number before the quiet period of acoustic emission is relatively high (usually more than 500), the fractal dimension Dt of the impact number is relatively high. When the value is greater than 0.3, rock burst may occur under the action of high and middle principal stress. The rock burst is destroyed very fast, the rock burst pit is deep, the damage degree and scope are large, and it is easy to cause large area burial in the tunnel, which is harmful to the actual project.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TU45
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