【摘要】：聲發(fā)射是一種常見的物理現(xiàn)象,大多數(shù)材料發(fā)生變形和斷裂時都會有聲發(fā)射現(xiàn)象出現(xiàn),如一些巖石的破壞等。聲發(fā)射現(xiàn)象與材料的破壞之間存在著一定的關(guān)系。隨著科學(xué)技術(shù)的發(fā)展,工程中出現(xiàn)了越來越多的深埋長大隧道,高地應(yīng)力問題成為了一個不可忽視的問題,研究發(fā)現(xiàn)巖石有記錄先前所受的歷史最高應(yīng)力的能力,即巖石的Kaiser效應(yīng),為準(zhǔn)確、便捷的測量地應(yīng)力提供了一種新的方法。近年來大量的研究人員對聲發(fā)射進(jìn)行了大量的研究,取得了許多可喜的成果,但是由于影響聲發(fā)射現(xiàn)象的因素眾多,不同的研究人員得到的結(jié)果也不盡相同。本文對砂巖樣本進(jìn)行了單軸壓縮實(shí)驗(yàn),利用自主搭建的聲發(fā)射信號采集系統(tǒng)采集砂巖樣本破壞過程中的聲發(fā)射信號,通過時域分析和頻域分析的方法研究砂巖破壞過程中不同破壞階段的聲發(fā)射信號特征,建立砂巖破壞過程與聲發(fā)射現(xiàn)象之間的對應(yīng)關(guān)系。本文還通過采用不同加載速率對砂巖樣本進(jìn)行單軸壓縮實(shí)驗(yàn),探討不同加載速率下砂巖聲發(fā)射信號的特征。同時本文采用單軸循環(huán)加載的方式,模擬巖石近期所受到的歷史最大應(yīng)力,對砂巖的Kaiser效應(yīng)進(jìn)行物理模擬研究,第一次加載的范圍為0KN-150KN,第二次加載的范圍為0KN-290KN,第三次加載的范圍為0KN-樣本破壞。并繪制不同幅值的荷載-振鈴累計(jì)曲線判斷Kaiser點(diǎn)的位置,對比不同幅值振鈴累計(jì)曲線所判別的Kaiser點(diǎn)位置的差異,提高Kaiser點(diǎn)的判別精度。通過實(shí)驗(yàn)發(fā)現(xiàn)：1、采用15KN/s、2.5KN/s加載速率對砂巖加載時,砂巖破壞過程的聲發(fā)射信號基本可以分為3個階段,初期階段、中期階段和后期階段,初期階段有較多的聲發(fā)射事件發(fā)生,中期階段屬于聲發(fā)射現(xiàn)象的平靜期,聲發(fā)射事件很少,在最后的后期階段,聲發(fā)射現(xiàn)象劇烈,過程中出現(xiàn)大量聲發(fā)射事件2、采用3.5KN/s加載速率加載時,初期階段和中期階段劃分不明顯,整個過程中均有大量聲發(fā)射事件發(fā)生,聲發(fā)射事件的分布較為均勻。3、砂巖破壞過程中聲發(fā)射信號頻帶分布較廣,在0-100KHz內(nèi)均有分布,并且在不同的破壞階段,聲發(fā)射信號的頻率分布有所不同。4、砂巖在循環(huán)加載過程中,在第一次加載的最大荷載150KN附近和第二次加載的最大荷載290KN附近,振鈴累計(jì)曲線均有明顯的轉(zhuǎn)折點(diǎn)即Kaiser點(diǎn)位置,說明砂巖可以記憶先前所受的歷史最高應(yīng)力。5、統(tǒng)計(jì)不同幅值的振鈴累計(jì)曲線得到所確定的Kaiser點(diǎn)的位置存在差異,選擇大于2倍和大于10倍的背景噪聲幅值的振鈴確定Kaiser點(diǎn)位置誤差較大,選擇大于3倍、4倍、5倍背景噪聲幅值的振鈴確定的Kaiser點(diǎn)位置精度較高。
[Abstract]:Acoustic emission (AE) is a common physical phenomenon. Most materials will have acoustic emission phenomena when they are deformed and fractured, such as the failure of some rocks. There is a certain relationship between acoustic emission phenomenon and material failure. With the development of science and technology, more and more deep-buried large tunnels have appeared in the engineering, and the problem of high in-situ stress has become a problem that can not be ignored. The study found that the rock has the ability to record the highest stress in history. That is, the Kaiser effect of rock provides a new method for accurate and convenient measurement of in-situ stress. In recent years, a large number of researchers have carried out a lot of research on acoustic emission, and achieved a lot of gratifying results. However, due to the many factors affecting the phenomenon of acoustic emission, the results obtained by different researchers are not always the same. In this paper, the uniaxial compression test of sandstone samples is carried out, and the acoustic emission signals during the failure process of sandstone samples are collected by an acoustic emission signal acquisition system built by itself. The characteristics of AE signals in different failure stages in sandstone failure process are studied by means of time domain analysis and frequency domain analysis, and the corresponding relationship between sandstone failure process and acoustic emission phenomenon is established. Through uniaxial compression experiments on sandstone samples with different loading rates, the characteristics of acoustic emission signals of sandstone under different loading rates are also discussed in this paper. At the same time, the historical maximum stress of rock is simulated by uniaxial cyclic loading, and the Kaiser effect of sandstone is studied by physical simulation. The range of the first loading is 0KN 鈮，

本文編號：2472726