【摘要】：巖體介質(zhì)超聲波測(cè)試技術(shù)是近四十多年發(fā)展起來的一種新技術(shù),它通過測(cè)定超聲波穿透巖體后聲波信號(hào)的聲學(xué)參數(shù)的變化,間接地了解巖石或巖體的物理力學(xué)特性、結(jié)構(gòu)構(gòu)造特征及應(yīng)力狀態(tài),已得到國內(nèi)外巖土工程界的廣泛重視。巖石在單軸受壓過程中內(nèi)部會(huì)產(chǎn)生破壞,根據(jù)超聲波參數(shù)特征可以判斷巖樣受壓過程中所處狀態(tài),從而對(duì)巖石的彈性極限以及應(yīng)力應(yīng)變特征的研究提供了更多的參考意義。本文主要通過對(duì)不同含水飽和度的紅砂巖在單軸加載過程中進(jìn)行超聲波測(cè)試,研究不同含水率巖石在單軸加載條件下超聲波的傳播特性,實(shí)驗(yàn)通過對(duì)巖石應(yīng)力應(yīng)變曲線以及超聲波參數(shù)的分析,研究飽水度對(duì)巖石強(qiáng)度和聲波參數(shù)的影響、巖石的彈性特征等。研究結(jié)果表明:(1)巖石聲波波速隨壓力增大先增大后減小。這是由于在低壓時(shí)巖石內(nèi)部小的孔隙易于閉合,當(dāng)大量的孔隙閉合時(shí),聲波波速會(huì)出現(xiàn)明顯的增大現(xiàn)象;隨著壓力增加,閉合的孔隙重新張開、新的微裂隙的產(chǎn)生并擴(kuò)展使得波速出現(xiàn)減小。(2)巖石飽水度對(duì)巖石物理力學(xué)性質(zhì)影響很大,隨著巖石含水率增加,其抗壓強(qiáng)度呈非線性減小。巖石飽水過程中,巖石礦物顆粒表面和孔壁的吸附水對(duì)巖樣的彈性模量和強(qiáng)度影響較大,也即水 巖作用導(dǎo)致的巖石礦物顆粒軟化、顆粒間聯(lián)結(jié)減弱等劣化效應(yīng)明顯較大。(3)巖石含水率對(duì)聲波參數(shù)的影響。巖樣在自然飽水過程中,聲波波速隨巖樣含水飽和度的增加而降低,從干燥狀態(tài)至飽水度70%過程中,波速緩慢減小并且呈線性趨勢(shì),從飽水度70%至100%時(shí),波速下降速度明顯變快;聲波波幅隨巖樣含水飽和度的增加出現(xiàn)先減小后增大的情況,可用二次函數(shù)進(jìn)行擬合,從干燥狀態(tài)至飽水度50%時(shí),波幅出現(xiàn)明顯下降,從飽水度50%至80%左右時(shí),波幅達(dá)到最低值,從飽水度80%至100%時(shí),波幅出現(xiàn)明顯上升。
[Abstract]:Ultrasonic testing technology for rock mass media is a new technology developed in recent forty years. It can indirectly understand the physical and mechanical properties of rock or rock mass by measuring the change of acoustic parameters of acoustic signal after ultrasonic wave penetrating rock mass. Structural characteristics and stress state have been widely paid attention to in geotechnical engineering field at home and abroad. Rock will be destroyed in the process of uniaxial compression. According to the characteristics of ultrasonic parameters, the state of rock sample under compression can be judged, thus providing more reference significance for the study of elastic limit and stress-strain characteristics of rock. In this paper, the ultrasonic propagation characteristics of rocks with different moisture content under uniaxial loading are studied by ultrasonic testing of red sandstone with different water saturation during uniaxial loading. Through the analysis of stress-strain curves and ultrasonic parameters of rock, the influence of saturation degree on rock strength and acoustic wave parameters, and the elastic characteristics of rock are studied in the experiment. The results show that: (1) the velocity of rock acoustic wave increases first and then decreases with the increase of pressure. This is due to the fact that the small pores in the rock are easy to close at low pressure, and when a large number of pores are closed, the acoustic wave velocity will increase obviously. With the increase of pressure, the closed pores re-open, and the new microcracks appear and expand to reduce the wave velocity. (2) the saturation degree of rock has a great influence on the physical and mechanical properties of rock, and with the increase of water content of rock, The compressive strength is reduced in a nonlinear manner. In the process of saturated rock, the absorption water of rock mineral particle surface and pore wall has great influence on the elastic modulus and strength of rock sample, that is, the softening of rock mineral particle caused by water rock action. (3) the influence of rock water content on acoustic parameters. In the process of natural saturation, the acoustic wave velocity decreases with the increase of water saturation of rock samples. From dry state to 70% saturation, the wave velocity decreases slowly and linearly, from 70% to 100%. The decreasing speed of wave velocity becomes faster obviously. The amplitude of acoustic wave decreases first and then increases with the increase of water saturation of rock samples. It can be fitted by quadratic function. From the dry state to 50 degree of saturation, the amplitude of wave amplitude decreases obviously, and the amplitude decreases from 50% to 80%. The amplitude of the wave reached the lowest value, from 80% to 100%, the amplitude increased obviously.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：TD315

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