共查询到17条相似文献，搜索用时 203 毫秒
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用三维梁-颗粒模型BPM3D(beam-particlemodelinthreedimensions)对岩石类非均质脆性材料的力学性质和破坏过程进行了数值模拟。梁-颗粒模型是在离散单元法基础上,结合有限单元法中的网格模型提出的用于模拟岩石类材料损伤破坏过程的数值模型。在模型中,材料在细观层次上被离散为颗粒单元集合体,相邻颗粒单元由有限单元法中的弹脆性梁单元联结。梁单元的力学性质均按韦伯(Weibull)分布随机赋值,以模拟岩石类材料力学参数的空间变异性。材料内部裂纹通过断开梁单元来模拟。通过自动生成的非均质材料模型对岩石类材料的破坏机理进行研究。岩石类非均质脆性材料在单轴压缩状态下破坏过程细观数值模拟结果显示,岩石材料宏观破坏是由于其内部细观裂纹产生、扩展、贯通的结果。通过数值模拟结果之间的对比分析,揭示出岩石试样宏观破坏模式随细观层次上韦伯分布参数的变化而不同。与实际矿柱破坏形态的对比分析表明了模型的适用性。根据数值模拟结果对岩石类非均质材料的破坏机理进行了探讨。 相似文献
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冲击载荷作用下准脆性材料Ⅱ型裂纹扩展研究 总被引：1，自引：0，他引：1
冲击载荷作用下准脆性材料的动态断裂一直是关注的热点问题,Ⅱ型裂纹试样受冲击剪切时其裂纹扩展方向同材料力学性质和冲击速度等密切相关。应用岩石动态破裂过程动态分析系统软件,对单边平行双裂缝试样开展了冲击载荷作用下的裂纹动态扩展数值模拟,分别研究了不同材料力学性质、材料均质度、入射应力脉冲幅值和历时对II型裂纹动态扩展的影响。数值模拟结果表明,纯II型裂纹在动荷载作用下的扩展,不仅受到剪切损伤,而且还存在拉伸损伤;准脆性材料的非均匀性导致了主裂缝周围产生大量微裂纹的破坏,影响裂缝的分岔和内部的应力值;应力幅值和应力脉冲历时分别超过某一定值时,主裂缝将出现分叉现象,试样的破坏程度加剧,其研究结果对于深入揭示准脆性材料在动荷载作用下II型裂纹扩展的规律及准脆性材料的损伤断裂机制具有重要的参考价值。 相似文献
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《岩土力学》2018,(Z2)
四川盆地龙马溪组页岩具有较好的生烃潜力。为研究龙马溪组页岩力学特性,首先对完整页岩试样开展了单轴压缩试验,基于颗粒流离散单元法反演单轴压缩岩石动态破坏过程,通过模拟常规三轴压缩试验,研究不同应力条件下页岩脆性破坏特征。研究表明,该龙马溪组页岩脆性矿物含量高,强度大,脆性特征明显;不同应力条件下龙马溪组页岩发生脆性破坏时具有相似的破坏特征,且峰值强度符合Mohr-Coulomb线性规律。加载到岩石损伤应力以前,微裂纹的分布无明显方向性和区域性,该时微裂纹的分布应与岩石的非均质性有关;损伤应力后微裂纹的萌生、聚集和贯通将受应力影响。页岩的特征应力(起裂应力、损伤应力、峰值强度)与围压表现出强相关性,但围压对峰值应力的影响程度比对损伤应力和起裂应力的影响程度更大,因裂纹稳定扩展阶段,微裂纹独立产生无相互影响,峰值应力还需考虑微裂纹间的相互作用及形成的宏观破裂面粗糙性的影响。 相似文献
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对称和非对称载荷下声发射特征的数值模拟研究 总被引：3，自引：0，他引：3
利用自行开发的岩石破裂过程分析RFPA^2D系统，研究了对称载荷和非对称载荷下岩样的破坏过程以及破坏过程中所呈现的声发射特征。数值模拟结果演示两种条件下由微破裂诱致宏观破坏的演化过程以及和微破裂相关的声发射事件源的空间分布特征和事件序列特征。数值模拟结果指出，和对称载荷压缩实验相比，两者的最大区别在于在非对称载荷压缩实验中局部的剪切破坏的发生以及一个更加局部化的声发射事件源分布。从物理意义上讲非对称载荷实验提供了在预定破裂路径下研究脆性破坏的方法，从声发射研究方面来说非对称实验比对称实验能更好地观察声发射事件源的局部化。 相似文献
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通过轮廓法追踪岩石裂纹扩展轨迹,将其嵌入ABAQUS扩展有限元（EFE）平台,对单轴压力下裂隙试件受压过程进行了模拟验证,裂纹起裂扩展效果良好。以此为平台,将推导得到的弧形裂纹应力强度因子嵌入其中,以最大周向拉应力准则为开裂准则,认为当其大于岩体断裂韧度时,硐室围岩体内初始裂纹将开始扩展。在此基础上,以发现分区破裂现象的圆形隧道模型试验为背景开展了分区破裂的数值模拟试验。模拟结果发现,深部巷道围岩出现了3~4层破裂分区,证实深部巷道围岩存在分区破裂现象。将数值模拟结果与模型试验完成后模型围岩破坏状态对比,发现二者破裂区分布特征基本一致。数值模拟结果表明,EFEM方法在处理复杂岩体裂纹问题方面的有效性。 相似文献
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将数字图像技术与Munjiza提出的有限元法-离散元法（FDEM）耦合分析方法结合,研制了可表征岩石真实非均质性的FDEM分析系统,为从细观角度对岩体进行建模以及研究岩体的破裂机制提供了新途径。该系统借助数字图像技术从岩石断面的图像获取岩石材料的真实细观结构,借助成熟的网格剖分技术,将其映射到FDEM计算网格中,从而克服了原有FDEM在考虑材料非均质性所存在的不足。利用该系统,进行了巴西圆盘劈裂试验的数值模拟,再现了花岗岩在荷载作用下的真实破裂过程。数值模拟结果表明,考虑非均质性的岩样应力分布呈现出非对称性,岩石的细观结构对岩石中裂纹的扩展及应力分布有重要影响。 相似文献
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The process of cutting homogeneous soft material has been investigated extensively. However, there are not so many studies on cutting heterogeneous brittle material. In this paper, R‐T2D (Rock and Tool interaction), based on the rock failure process analysis model, is developed to simulate the fracture process in cutting heterogeneous brittle material. The simulated results reproduce the process involved in the fragmentation of rock or rock‐like material under mechanical tools: the build‐up of the stress field, the formation of the crushed zone, surface chipping, and the formation of the crater and subsurface cracks. Due to the inclusion of heterogeneity in the model, some new features in cutting brittle material are revealed. Firstly, macroscopic cracks sprout at the two edges of the cutter in a tensile mode. Then with the tensile cracks releasing the confining pressure, the rock in the initially high confining pressure zone is compressed into failure and the crushed zone gradually comes into being. The cracked zone near the crushed zone is always available, which makes the boundary of the crushed zone vague. Some cracks propagate to form chipping cracks and some dip into the rock to form subsurface cracks. The chipping cracks are mainly driven to propagate in a tensile mode or a mixed tensile and shear mode, following curvilinear paths, and finally intersect with the free surface to form chips. According to the simulated results, some qualitative and quantitative analyses are performed. It is found that the back rake angle of the cutter has an important effect on the cutting efficiency. Although the quantitative analysis needs more research work, it is not difficult to see the promise that the numerical method holds. It can be utilized to improve our understanding of tool–rock interaction and rock failure mechanisms under the action of mechanical tools, which, in turn, will be useful in assisting the design of fragmentation equipment and fragmentation operations. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Natural damage such as fissures and pores make the rock microstructure show strong heterogeneity,which influences the failure process and mode. In this paper,the numerical test of freeze-thaw sandstone splitting failure with natural damage was carried out based on CT non-destructive identification technology,combined with digital image processing technology and CASRock numerical simulation software. The analysis of splitting failure mode,deformation localization and crack evolution process of freeze-thaw sandstone with natural damage reveals the failure mechanism of sandstone with natural damage under freeze-thaw and load. The results show that the expansion of primary pores（cracks）and the formation of new pores in sandstone are the main forms of freeze-thaw rock failure evolution. The failure of rock containing natural damage under freeze-thaw and load is related to the degree and distribution of natural damage. The generation of secondary cracks mostly occurs in natural damage-intensive areas. During the loading process,the stress in the localized damage zone is far greater than sandstone’s overall stress,and rock’s failure in the localized damage zone is synchronized with the energy release and stress release in the region. Localized damage reflects the evolution of cracks in rocks and helps to predict the direction of sandstone crack development. The failure mode of rock is related to the number of freeze-thaw cycles. The freeze-thaw cycles make the sandstone with natural damage gradually change from brittle failure to ductile failure,and the change of the overall strength of the rock is a gradual deterioration process. © 2022 Science Press (China). 相似文献
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孔口问题为力学领域中经典问题之一,也是岩土如隧洞、巷道等工程领域重要的问题之一。随断裂力学的发展,对含裂纹孔口问题的研究也不断深入。但是,以往研究多集中在二维问题或者含表面裂纹的孔口问题,含纯内裂纹的孔口问题研究报道较少。基于3D-ILC技术（对表面无任何影响的情况下,凭空生成任意参数的深埋内裂纹）,在含有孔口的脆性材料中生成内裂纹,开展单轴压缩试验,与无裂纹完整孔口试样试验结果及已有文献进行对比,并开展理论与数值模拟研究。结果表明：（1）3D-ILC与传统方法相比,裂纹特征更为真实,为解决断裂力学中的三维内裂纹问题奠定了基础;（2）完整孔口试样裂纹形态主要有主裂纹与八字形裂纹;（3）含内裂纹试样裂纹形态以内裂纹扩展为主,主要有翼裂纹、次生裂纹、反翼裂纹、反向次生裂纹、竖向扭曲裂纹与主裂纹6种;（4）含裂纹孔口试样最终的破坏荷载比无裂纹孔口试样平均低76.49%,起裂应力较无裂纹孔口试样平均低96.72%;（5）通过数值模拟对完整孔口试样、含主裂纹孔口试样、含内裂纹孔口试样的裂纹扩展进行定性分析,与试验结论一致。该研究结果为含三维内裂纹的孔口脆性材料的断裂理论研究提供了物理试验基础。 相似文献
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Cheng Zhao Yimeng Zhou Qingzhao Zhang Chunfeng Zhao Hiroshi Matsuda 《国际地质力学数值与分析法杂志》2020,44(3):353-370
To deeply understand the cracking mechanical behavior of brittle rock materials, numerical simulations of a rock specimen containing a single preexisting crack were carried out by the expanded distinct element method (EDEM). Based on the analysis of crack tips and a comparison between stress- and strain-based methods, the strain strength criterion was adopted in the numerical models to simulate the crack initiation and propagation processes under uniaxial and biaxial compression. The simulation results indicated that the crack inclination angle and confining pressure had a great influence on the tensile and shear properties, peak strength, and failure behaviors, which also showed a good agreement with the experimental results. If the specimen was under uniaxial compression, it was found that the initiation stress and peak strength first decreased and then increased with an increasing inclination angle α. Regardless of the size of α, tensile cracks initiated prior to shear cracks. If α was small (such as α ≤ 30°), the tensile cracks dominated the specimen failure, the wing cracks propagated towards the direction of uniaxial compression, and the propagation of shear cracks was inhibited by the high concentration of tensile stress. In contrast, if α was large (such as α ≥ 45°), mixed cracks dominated the specimen failure, and the external loading favored the further propagation of shear cracks. Analyzing the numerical results of the specimen with a 45° inclination angle under biaxial compression, it was revealed that lateral confinement had a significant influence on the initiation sequence and the mechanical properties of new cracks. 相似文献
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最新研制了一种完全透明、较低温度下拉压比可达1/6.6的树脂,其与岩石特性的相似性较前人的研究有大幅度提高。制作了一组含三维内置平行双裂隙组的试件,详细描述并分析了单轴加载下试件的裂隙扩展与贯通过程,研究其产生的条件和机制。试验结果表明：试件的破坏大致经历4个阶段,三维裂隙组的断裂比二维情况复杂得多,产生了多种不同形态的裂纹。在FLAC3D软件框架内建立了一种新的弹脆性本构关系,并采用超细单元和合理形态的网格建模。将数值模拟结果与相关试验进行对比,相符程度良好,表明新数值模拟方法的有效性。当双轴加载时,模拟结果也与前人类似试验结果有很好一致性。 相似文献
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储层非均质性对水力压裂的影响 总被引：1，自引：0，他引：1
从岩石细观非均质性的特点出发,采用RFPA2D-Flow软件对单孔和双孔数值模型进行压裂计算,研究岩石非均质性对水力压裂的响应,重点探讨双孔模型孔间吸引效应对裂纹演化形态的影响。岩石细观单元的力学、水力学特性由统计分布生成以体现岩石的随机不均质性,水力压裂过程中流体压力传递通过单元渗流-损伤耦合迭代来实现。数值计算结果表明:(1)岩石非均质性影响裂缝的扩展形态,导致水力裂纹尖端微裂纹的分支。随着均质度的增加,水力裂纹的扩展形态变得更加平直光滑,单孔模型两侧裂纹更加对称,双孔间裂纹的连通性变差。(2)岩石的非均匀性对于岩石的起裂压力和地层破裂压力影响较大。随着均质度的增大,起裂应力和地层破裂应力增大,并且两者间的差值逐渐变小,在储层为均质的条件下,两者几乎相等。(3)相同的边界条件下,均质模型的应力分布曲线光滑连续,非均质模型的应力分布曲线呈现出明显波动,井眼对称剖面上的应力分布不尽相同,反映了细观单元强度非均匀性及裂缝扩展形态对应力分布的影响。(4)双孔模型孔间存在孔隙水压力增加带,孔间产生吸引效应,双孔方位影响临界压力。研究结果对水压裂试验设计和现场压裂施工具有一定的参考意义。 相似文献
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Q3黄土的单轴拉伸试验表明,黄土的抗拉强度值很小,在拉张应力作用下会发生突发性的脆性破坏,断裂面粗糙,且基本垂直于拉应力方向。借助数值分析软件RFPA,对黄土的整个拉张破裂过程进行了仿真分析,捕捉到了黄土在拉张应力作用下内部裂纹的扩展与演化过程。结果表明,黄土的拉张破裂过程可以分为两个阶段,即线性变形阶段和裂纹的形成、扩展与贯通阶段。黄土体内部裂纹的萌生、扩展及贯通会在很短时间内完成,即黄土在拉伸应力作用下的破坏是突发性的,属于脆性断裂。单轴拉伸试验结果与数值仿真分析结果具有较好的一致性。 相似文献