本文選題：裂紋試樣 + 破壞模式��； 參考：《重慶大學》2015年碩士論文

【摘要】：由于復雜的地質(zhì)構(gòu)造和賦存條件,巖石是一種典型的不連續(xù)介質(zhì),存在一些如礦物解理、微裂隙、粒間空隙、晶格缺陷等內(nèi)部缺陷。國內(nèi)外學者經(jīng)過大量研究發(fā)現(xiàn),在受力的情況下,這些軟弱結(jié)構(gòu)面會張開、擴展并貫通引起巖石的失穩(wěn)甚至破壞。因此,進行含預制裂紋試樣的相似模型試驗研究,對實際工程有重要的指導意義。關(guān)于含兩根預制裂紋的試樣,學者們做了大量的研究工作,但沒有綜合考慮空間布置對試樣破壞過程的影響。本文為了研究裂紋空間布置因素對起裂模式、破壞模式、試樣力學特性以及試樣表面位移變化的影響,基于聲發(fā)射和圖像處理技術(shù)主要做了以下工作并取得了相應成果:①對預制裂紋尖端微裂紋出現(xiàn)的先后順序進行了描述,并對新生裂紋的類型進行了歸類:翼型裂紋,次生共面裂紋和次生傾斜裂紋�？紤]了裂紋的空間布置因素對起裂模式和破壞模式影響:隨著裂紋傾角增大,當裂紋間距比較小時,試樣破壞模式由剪切破壞向張拉破壞轉(zhuǎn)變,而當裂紋間距比較大時,試樣破壞模式在張拉破壞的幾種模式之間轉(zhuǎn)變;隨著裂紋間距的變大,試樣由剪切破壞向張拉破壞轉(zhuǎn)變;隨著裂紋未連通率變化,試樣破壞模式主要在張拉破壞的幾種模式之間轉(zhuǎn)變。②分析在不同空間分布下試樣的應力-應變曲線,考慮了裂紋的空間布置因素對試樣力學特性的影響:隨著裂紋傾角的變大,試樣的起裂應力有先減小后增大的,也有一直增大的,而峰值應力有先增大后減小的,也有一直增大的;隨著裂紋間距的變大,試樣的起裂應力和峰值應力都是先減小后增大;隨著裂紋未連通率變小,試樣的起裂應力和峰值應力都是先減小后增大。③根據(jù)試樣破壞過程中的聲發(fā)射數(shù)據(jù)和應力應變曲線,分析每個試樣破壞過程中的聲發(fā)射特征,得到如下結(jié)論:剪切破壞模式中產(chǎn)生聲發(fā)射事件的水平比較低,其變化趨勢與應力應變曲線基本一致;張拉破壞模式中產(chǎn)生聲發(fā)射事件的水平比較高,其變化趨勢與應力應變曲線有較大的不同。④通過觀察試樣的位移矢量圖和數(shù)值模擬結(jié)果,分析了裂紋起裂和試樣破壞時的位移變化情況,得到如下結(jié)論:起裂時,試樣變形一般以壓縮變形為主,試樣一般有向下方移動的趨勢;破壞時,試樣表面位移改變比較大,有明顯的相對滑移現(xiàn)象;根據(jù)裂紋空間布置的不同,相對滑移面沿主對角線或副對角線。
[Abstract]:Because of the complex geological structure and occurrence conditions, rock is a typical discontinuous medium, which has some internal defects such as mineral cleavage, microcracks, intergranular voids, lattice defects and so on. Through a large number of studies at home and abroad, it is found that under the condition of force, these weak structural planes will open, expand and pass through, which will lead to rock instability and even destruction. Therefore, it is of great significance for practical engineering to study the similar model test of specimens with precast cracks. A lot of research work has been done on the specimens with two precast cracks, but the influence of the spatial arrangement on the failure process of the specimens has not been considered synthetically. In order to study the effect of crack space arrangement on fracture initiation mode, failure mode, specimen mechanical properties and surface displacement, Based on the acoustic emission and image processing techniques, the following works have been done and corresponding results have been obtained: 1. The sequence of microcracks at the tip of prefabricated cracks is described, and the types of new cracks are classified as airfoil cracks. Secondary coplanar crack and secondary inclined crack. The effect of the space arrangement of the crack on the initiation mode and the failure mode is considered. With the increase of the dip angle of the crack, when the crack spacing is small, the failure mode of the specimen changes from shear failure to tensile failure, and when the crack spacing is large, the fracture mode changes from shear failure to tensile failure. The fracture mode of the specimen changes between several modes of tensile failure; with the increase of crack spacing, the specimen changes from shear failure to tensile failure; and with the change of crack unconnectivity, The failure mode of specimens is mainly transformed between several modes of tensile failure. 2. The stress-strain curves of specimens with different spatial distributions are analyzed. The effect of the space arrangement of the crack on the mechanical properties of the specimen is considered. With the increase of the crack inclination angle, the initial crack stress of the specimen decreases first and then increases, and the peak stress increases first and then decreases. With the increase of crack spacing, the crack initiation stress and peak stress of the specimen decrease first and then increase; with the crack unconnected ratio becoming smaller, the crack initiation stress and the peak stress increase with the increase of crack spacing. The initial crack stress and peak stress of the specimen are reduced first and then increased .3 according to the acoustic emission data and the stress-strain curve during the failure process of the specimen, the characteristics of the acoustic emission in the failure process of each specimen are analyzed. The conclusions are as follows: the level of acoustic emission events in shear failure mode is relatively low, and the variation trend is basically consistent with the stress-strain curve, and the level of acoustic emission events in tensile failure mode is relatively high. The variation trend is quite different from the stress-strain curve. 4 by observing the displacement vector diagram and the numerical simulation results of the specimen, the variation of the displacement during the crack initiation and the specimen failure is analyzed, and the following conclusions are obtained: when the crack starts, The deformation of the specimen is mainly compression deformation, and the specimen tends to move downwards. During the failure, the surface displacement of the specimen changes greatly and there is obvious relative slip phenomenon. According to the different space arrangement of the crack, the deformation of the specimen is mainly compressed, and the specimen tends to move downwards. The relative slip surface is along the main diagonal line or the secondary diagonal line.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU45

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