共查询到18条相似文献，搜索用时 164 毫秒
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压缩作用下岩石内部细观裂纹扩展导致岩石产生损伤,其对岩石变形、强度等力学特性有着重要影响;然而,岩石内部裂纹扩展与剪切特性（黏聚力、内摩擦角及剪切应力）动态演化关系很少被研究。基于裂纹扩展机制推出的岩石应力-应变本构模型,并结合摩尔-库仑失效准则,推出了在岩石应力-应变关系峰值应力（对应岩石压缩强度）状态时,本构模型细观力学参数与岩石黏聚力、内摩擦角及剪切强度之间的状态关系。然后,引入岩石应力-应变本构关系塑性变形阶段服从摩尔-库仑屈服准则的力学流动规律,进而将已推出的应力-应变关系峰值状态点所满足的细观力学参数与黏聚力、内摩擦角关系,推广到岩石进入塑性变形后,岩石内部裂纹扩展（或应变）与黏聚力、内摩擦角及剪切应力动态演化的理论关系。随着裂纹扩展或应变增加,黏聚力、内摩擦角及剪切应力先增大,达到一个峰值点后减小,该结果与应力-应变本构曲线变化趋势相对应。通过试验结果验证了所提出理论结果的合理性。并讨论了初始裂纹之间摩擦系数对黏聚力、内摩擦角及剪切应力随裂纹扩展或应变演化规律的影响。 相似文献
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水压和应力耦合下脆性岩石蠕变与破坏时效机制研究 总被引：2，自引：0，他引：2
基于水压和应力耦合作用下锦屏深部大理岩的三轴蠕变试验,研究了大理岩的变形时效特性、等时曲线特征以及时效破坏机制。研究结果表明,(1) 孔隙水压可以增强大理岩的时效变形能力,有水压时的稳态蠕变率大于无水压状态时的稳态蠕变率。(2) 裂纹扩容失稳应力强度比可以作为硬脆性岩石是否发生失稳蠕变的门限值,且当应力强度比到达这一门限值时,岩石的失稳概率随着时间发展而陡增。(3) 体积蠕变量大于侧向和轴向的蠕变量值,显示脆性岩石扩容蠕变效应特征显著。(4) 不同时刻的等时曲线具有明显的相似性,在发生加速蠕变之前,等时曲线基本呈线性特征;而在发生加速蠕变时,等时曲线呈显著非线性特征。 相似文献
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应变率对红砂岩渐进破坏过程和特征应力的影响 总被引：6，自引：0，他引：6
为了深入研究脆性岩石的渐进破坏过程,利用RMT-150C型岩石力学试验系统对产自鲁南地区的一种红砂岩进行了系统的力学性质试验研究,得出该类型砂岩试样在不同应变率条件下的力学表现。将试件的渐进破坏过程通过特征应力分为裂纹闭合阶段、线弹性变形阶段、裂纹起裂和稳定扩展阶段以及裂纹不稳定扩展阶段,通过对应力-应变曲线、轴向变形刚度、体积应变曲线和裂纹体积应变等数据的分析,以及采用动点回归技术确定了试样的起裂应力和致损应力,并进一步研究了该类红砂岩的渐进破坏过程及红砂岩峰值强度、起裂应力等参数和应变率之间的关系。试验结果表明,随着应变率的增加,红砂岩试样的峰值强度先降低后提高,起裂应力及致损应力与峰值强度的比值均有所降低。分析了红砂岩峰值强度变化的物理机制并给出了解释,研究了应变率对红砂岩渐进破坏过程的影响 相似文献
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压剪应力条件下各向异性岩石损伤本构模型和渗流模型(Ⅰ)：理论模型 总被引：4，自引：4，他引：0
采用细观力学研究了岩石损伤变形过程和渗流过程。在本构模型中增加了对剪胀变形机理和渗流对变形影响的内容,同时按照微裂纹发展过程建立了考虑微裂纹扩展、变形和渗透压影响的岩石各向异性渗流模型,使得模型能够更好地表述岩石的变形特性和渗流特性。所建立的模型能够考虑微裂纹闭合摩擦滑移、微裂纹发生自相似扩展和微裂纹发生弯折扩展等过程。 相似文献
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对含预制裂纹的花岗岩进行单轴压缩试验研究预制裂纹倾角α对脆性岩石渐进性破坏过程的影响。首先埘破坏过程的轴向应力-横向应变曲线进行总结和讨论,然后分析预制裂纹与加载方向夹角α埘岩石的应应力门槛值：裂纹起始应力σci、裂纹扩展应力σed、峰值强度矿σf,由应变片记录的应力-应变曲线和试样的表嘶裂纹扩展情况的影响机制。结果表明,含有预制裂纹的岩石试样进行加载试验过程中,顶制裂纹倾角α的变化成了决定脆性岩石破裂办式的主要因素。故在对含节理、裂隙的脆性岩石的工程应用上,通过对岩休的轴向应力-横向应变向应变典线进行分析,可以对地下开挖工程起到指导设计开挖方式及支护形式的作用。 相似文献
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高渗压条件下压剪岩石裂纹断裂损伤演化机制研究 总被引：2，自引：1，他引：1
探讨了高渗透压作用下压剪岩石裂纹的起裂规律及分支裂纹尖端应力强度因子的演变规律,建立了高渗压下裂隙岩体发生拉剪破坏的临界水压力值和初裂强度判据,分析了不同渗压作用下裂纹的扩展情况表明,渗透压的存在加剧了分支裂纹的扩展,高渗透压作用下分支裂纹扩展由稳定扩展变成不稳定扩展,并导致分支裂纹尖端岩桥剪切破坏,同时考虑分支裂纹的相互作用,建立了高渗透压作用下压剪岩石裂纹体岩桥剪切贯通的断裂破坏力学模型,最后依据裂隙岩体的损伤力学效应研究了岩体的初始损伤及损伤演化柔度张量,提出了高渗压下压剪岩石裂纹渐进破坏的损伤演化方程。该理论为定量研究高渗压下裂隙岩体的失稳破坏提供了理论依据。 相似文献
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能量变化是材料各参数变化的本质特征。通过颗粒流模拟岩石单轴压缩试验,从细观力学角度分析能量转化、裂纹扩展及损伤演化规律。颗粒流利用细观颗粒的运动克服了宏观力学理论不易实现试件多裂纹破坏形态的缺点,以此研究能量变化更加合理。应力-应变各阶段能量与微裂纹及损伤存在着相互对应的发展关系。通过3种工况论证了宏-细观力学参数对应关系,采用最小二乘法拟合得出微裂纹与轴向应变呈幂次函数关系。采用割线模量定义损伤变量,取模量加速下降处（对应裂纹加速扩展）为损伤门槛,对应损伤阈值为0.158。3种工况下微裂纹数量与损伤呈线性发展关系,为损伤演化的深入研究提供参考。 相似文献
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基于物理和常规变形特性分析,认为某水电站坝基碎屑岩力学特性异常复杂,故采用岩石三轴伺服仪开展了系列的蠕变力学特性试验研究。首先,探讨了轴向、侧向及体积蠕变特性和速率变化规律;其次,分析了蠕变对偏应力-应变特性影响并开展了破坏岩样微细观电镜扫描试验;最后,在采用等时曲线簇法确定长期强度的基础上,以实际延性扩容为依据,认为岩石侧向体积扩容速率大于轴向压缩速率的临界点为快速蠕变破坏的标志,提出确定长期强度的新方法。结果表明,碎屑岩表现出显著的蠕变特性,蠕变曲线主要分为初始衰减和稳态蠕变两阶段,且最后一级应力施加后呈现加速蠕变现象;应力增加导致蠕变变形加剧,最终破坏表现出轴向压缩变形过大、体积延性扩容明显、稳态蠕变速率较大等特点,且蠕变速率与应力符合指数函数关系。岩样长期强度与三向稳态蠕变速率交点和侧向体积扩容应力阀值基本一致,为常规强度的54%～80%。试验结果旨在为相关岩石工程长期稳定分析及蠕变模型构建提供可靠的依据。 相似文献
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岩石内部细观裂纹的存在,对压缩作用下岩石剪切断裂的宏观现象有着重要的影响。然而,能够通过解析解阐释细观裂纹几何特性、围压等影响因素对压缩作用下剪切断裂面角度变化趋势的研究很少。基于Ashby模型中提出的裂纹尖端应力强度因子,提出了一种改进的考虑裂纹角度影响的应力强度因子表达式。利用该改进的应力强度因子表达式,推出了一个可以预测岩石峰值强度的裂纹扩展、应变与应力之间的本构关系。结合本构关系的峰值强度与摩尔-库仑失效准则,得到了岩石损伤与内摩擦角、黏聚力、剪切强度及失效断裂面角度之间的理论关系;讨论了围压、裂纹尺寸、角度及摩擦系数对岩石宏观剪切断裂面角度的影响,通过试验结果验证了模型合理性。结果表明：随着损伤增大,内摩擦角、黏聚力及剪切强度不断减小;随着围压增大、摩擦系数增大和初始裂纹尺寸减小,剪切断裂面角度不断增大;随着裂纹角度增大,剪切断裂纹面角度先减小后增大。 相似文献
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高水压下岩体裂纹扩展的渗流-断裂耦合机制与数值实现 总被引：1，自引：0，他引：1
采用渗流力学、断裂力学理论结合Monte Carlo方法描述岩体裂纹的随机分布,研究高水压作用下岩体原生裂纹的变形和翼形裂纹的萌生、扩展、贯通的渗流-断裂耦合作用机制,建立高水压作用下岩体裂纹的渗流-断裂耦合数学模型,给出该数学模型的求解策略与方法,在Fortran95平台下开发高水压下岩体裂纹扩展的渗流-断裂耦合分析程序HWFSC.for。高水压下岩体裂纹扩展的渗流-断裂耦合体现在岩体裂纹网络和渗流初始条件都随渗流时步变化。对高压注水岩体裂纹扩展过程进行渗流-断裂耦合分析。结果表明,高压注水条件下,岩体裂纹扩展存在起动水压力,当水压力大于起动水压力时,裂纹尖端开始萌生翼形裂纹,随着裂纹水压力的增加,翼形裂纹扩展,进而与其他裂纹搭接贯通,停止扩展。渗流-断裂耦合分析考虑了裂纹动、静水压力对裂纹产生的法向扩张效应及翼形裂纹的扩展而形成新的渗流通道两方面的影响,连通裂纹数随渗流的发展而增加。岩体裂纹的渗流-断裂耦合分析,能较真实地再现岩体裂纹的水力劈裂现象,描述岩体裂纹的扩展、贯通过程及与之相耦合的渗流响应。 相似文献
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A micromechanics-based approach is proposed to predict the shear failure of brittle rocks under compression. Formulation of this approach is based on an improved wing microcrack model, the Mohr-Coulomb failure criterion, and a micro-macro damage model. The improved wing microcrack model considers the effects of crack inclination angle on mechanical behaviors of rocks. The micro-macro damage model describes the relation between crack growth and axial strain. Furthermore, comparing experimental and theoretical relations between crack initiation stress and confining pressure, model parameters (i.e., μ, a, β, and φ) hardly measured by test are solved. Effects of crack inclination angle, crack size, and friction coefficient on stress-strain relation, compressive strength, internal friction angle, cohesion, shear failure plane angle, and shear strength are discussed in details. A most disadvantaged crack angle is found, which is corresponding to the smallest compressive strength, cohesion, internal friction angle, and shear strength of rocks. Rationality of the theoretical results is verified by the published experimental results. This approach provides a theoretical prediction for effects of microcrack geometry on macroscopic shear properties in brittle rocks under compression. 相似文献
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裂隙的剪胀特性及扩展演化规律对岩体的渗流特性具有重要影响。为揭示裂隙剪胀及扩展演化对岩体渗流的影响,基于残余强度提出了一种能较好描述岩石硬化-软化特性的全剪切本构关系;结合剪切变形与裂隙开度的关系,利用最小势能原理和立方定律,建立了压剪作用下考虑裂隙剪胀特性的渗流应力耦合模型;假定压剪作用下裂隙发生Ⅰ型扩展,提出了伴有翼型裂纹的渗流模型,该模型不仅考虑了岩石的剪胀特性,更反映了裂隙扩展过程渗流的演化规律。对不同裂隙粗糙度的剪切应力-位移曲线进行分析,全剪切本构模型表现出较高的拟合精度。在剪切应力-位移关系基础上,通过剪切渗流试验数据对压剪作用下渗流模型进行验证,结果表明,该模型能较好地描述岩体剪胀阶段渗透性演化规律。利用等效裂隙简化裂隙网络,并通过试验数据进行验证,证实了裂隙扩展过程渗流-应力耦合模型的准确性与适用性。 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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干热岩水压致裂过程中低温诱导热应力与注入水压共同影响裂缝的萌生与扩展。首先通过THM耦合分析了低温压裂液注入过程中注入水压与热应力的相互作用及其对裂缝萌生的影响,随后建立描述岩石细观结构的THMD耦合模型对热应力影响下高温岩石水压致裂过程进行初探。结果表明：低温压裂液注入高温岩石产生的热应力包括岩石自身温度梯度形成的热应力与岩石颗粒非均匀膨胀导致的热应力,并在井筒周围呈现为拉应力。高注入压力将抑制热应力导致的多裂缝萌生,井筒附近热应力的存在对注入压力也具有削弱作用。基岩温度升高,裂缝萌生阶段更多裂缝在井筒附近起裂,缝网沿最大地应力方向的扩展速度减慢,但改造规模增加,同时多裂缝的存在也使得裂缝延伸压力增加。 相似文献
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Brittle fracture processes were hypothesized by several researches to cause a damage zone around an underground excavation in sulfate-rich clay rock when the stress exceeds the crack initiation threshold, and may promote swelling by crystal growth in newly formed fractures. In this study, laboratory experiments such as unconfined and confined compression tests with acoustic emission monitoring, and microstructural and mineralogical analyses are used to explain brittle fracture processes in sulfate-rich clay rock from the Gipskeuper formation in Switzerland. This rock type typically shows a heterogeneous rock fabric consisting of distinct clayey layers and stiff heterogeneities such as anhydrite layers, veins or nodules. The study showed that at low deviatoric stress, the failure behavior is dominated by the strength of the clayey matrix where microcracks are initiated. With increasing deviatoric stress or strain, growing microcracks eventually are arrested at anhydrite veins, and cracks develop either aligned with the interface between clayey layers and anhydrite veins, or penetrate anhydrite veins. These cracks often link micro-fractured regions in the specimen. This study also suggest that fracture localization in sulfate-rich clay rocks, which typically show a heterogeneous rock fabric, does not take place in the pre-peak range and renders unstable crack propagation less likely. Sulfate-rich clay rocks typically contain anhydrite veins at various scales. At the scale of a tunnel, anhydrite layers or veins may arrest growing fractures and prevent the disintegration of the rock mass. The rock mass may be damaged when the threshold stress for microcrack initiation is exceeded, thus promoting swelling by crystal growth in extension fractures, but the self-supporting capacity of the rock mass may be maintained rendering the possibility for rapidly propagating instability less likely. 相似文献
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Rock fracture under upper crustal conditions is driven not only by applied stresses, but also by time-dependent, chemically activated subcritical cracking processes. These subcritical processes are of great importance for the understanding of the mechanical behaviour of rocks over geological timescales. A macroscopic manifestation of time-dependency in the brittle field is the observation that rocks can deform and fail at constant applied stresses, a phenomenon known as brittle creep. Here, we review the available experimental evidence for brittle creep in crustal rocks, and the various models developed to explain the observations. Laboratory experiments have shown that brittle creep occurs in all major rock types, and that creep strain rates are extremely sensitive to the environmental conditions: differential stress, confining pressure, temperature and pore fluid composition. Even small changes in any of these parameters produce order of magnitude changes in creep strain rates (and times-to-failure). Three main classes of brittle creep model have been proposed to explain these observations: phenomenological, statistical, and micromechanical. Statistical and micromechanical models explain qualitatively how the increasing influence of microcrack interactions and/or the increasing accumulated damage produces the observed evolution of macroscopic deformation during brittle creep. However, no current model can predict quantitatively all of the observed features of brittle creep. Experimental data are limited by the timescale over which experiments are realistically feasible. Clearly, an extension of the range of available laboratory data to lower strain rates, and the development of new modelling approaches are needed to further improve our current understanding of time-dependent brittle deformation in rocks. 相似文献
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为研究水力耦合作用下砂岩裂纹扩展特征,开展了不同孔隙水压和围压条件的砂岩破坏试验。结果表明：有效围压相同,随着孔隙水压力增大,脆性指标数增大,起裂应力、损伤应力和峰值应力都变小;裂纹初始体积应变变小,裂纹扩展体积应变先减小后增大,损伤应力与峰值应力对应的裂纹轴向应变扩展速率、裂纹环向应变扩展速率增加,裂纹体积应变扩展速率与孔隙水压力关系不明显。孔隙水压力相同,随着有效围压增加,起裂应力、损伤应力和峰值应力增大。起裂应力、损伤应力、峰值应力对应的裂纹轴向应变扩展速率、裂纹环向应变扩展速率和裂纹体积应变扩展速率增大。同一块砂岩特征应力点的裂纹应变扩展速率比较,裂纹轴向应变扩展速率最大,裂纹环向应变扩展速率次之,裂纹体积应变扩展速率最小。 相似文献