共查询到19条相似文献，搜索用时 930 毫秒
1.
本文从各向异性线弹性体应力应变关系的一般表示式出发,通过矩阵代数运算,说明各向异性弹性介质的应力应变关系不仅取决于材料本身的力学性质,而且还依赖于偏应力作用的方向和材料物性对称面的相对几何关系。证明了在微小应变下,球应力张量不仅引起体变,而且也引起畸变;偏应力张量不仅引起畸变,而且也引起体变。通过简单的算例进一步阐明了这种剪胀性所服从的特殊规律。 相似文献
2.
自然界的土体通常具有各向异性的特点,而传统的破坏准则大多只适用于各向同性的土体。结合应力张量和反映材料各向异性状态的组构张量,定义了修正偏应力及其不变量,提出了适用于各向异性土体材料的破坏准则。给出了共轴条件下正交各向异性和横向各向异性材料在一般应力空间的破坏曲线以及不同应力区中主应力系数b与摩擦角的关系曲线,并分析了它们的特性以及与各向同性材料相应曲线的区别。通过与真三轴试验数据的比较,表明该准则能很好地描述各向异性土体材料的强度特点。 相似文献
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从发挥面的角度出发,分析论证各向异性是引起岩土材料出现非共轴现象的根本原因,得到与材料力学一致的结论。当共轭的两发挥面与沉积面的夹角不相等时,主应力面上将出现塑性应变增量的切向分量,所以塑性应变增量的主方向与应力的主方向非共轴。按照这一结论,对非共轴的数值模拟,也应当根据各向异性本构模型进行。为考虑各向异性影响新近提出的各向异性变换应力法,改变了各应力分量的相对大小,得到的各向异性变换应力张量与真实应力张量的主方向不一致,因此也能反映非共轴。利用各向异性变换应力法,能够在现有的弹塑性本构模型的框架下,描述土的非共轴现象。以各向异性UH模型为例,预测各种加载条件下的非共轴变形,验证了该方法的有效性。 相似文献
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基于微结构张量理论的柱状节理岩体各向异性强度分析 总被引：2，自引：0，他引：2
复杂的结构面是控制岩体力学性质的主要因素,由结构面引起的岩体各向异性一直是岩体力学研究的热点问题。柱状节理是一类特殊的岩体地质结构面,具有强烈的各向异性特性,微结构张量理论是目前国际岩石力学领域一种较有效地探讨结构面各向异性问题的新方法。材料的微结构张量和加载向量是微结构张量法描述的两个重要参量。采用多组节理面局部坐标系与整体坐标系的投影关系,定义了材料的微结构张量计算方法,引入各向异性参数ψ表述微结构张量在加载方向的投影,将其引入Jaeger针对岩体沿节理面滑动破裂提出的基于Mohr-Coulomb强度准则,得到了多组节理岩体的各向异性强度准则。同时,结合白鹤滩坝址区的柱状节理特性,分析柱状节理引起的各向异性对坝址区稳定性的影响 相似文献
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热液矿床成矿深度受成矿期构造空间的控制,构造空间为古构造应力场所致。构造应力场中偏应力张量为零的深度是构造变形的极限部位,岩石的强度极限与偏应力张量达到零值的叠加部位是成矿的极限深度。 相似文献
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本文将岩体中的宏观裂隙体视为岩体的一种初始损伤，给出了岩体的各向异性宏观损伤张量与裂隙间断位移引起的损伤应变张量，建立了以岩体体平均应力、应变为基本变量的等效连续模型。同时，我们还讨论了如何通过现场工程地质调查，以获取确定岩体宏观损伤性质的工程地质信息． 相似文献
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钙质砂是海洋钙质生物死亡后形成的一种具有丰富内部孔隙、低强度、不规则形状和易破碎的岩土材料。通过对钙质砂分别开展的等向压缩、常规三轴压缩、平均主应力为常数的三轴压缩、减压的三轴压缩和等应力比加载5种试验,探讨了不同应力路径下钙质砂的力学及变形特性。试验结果表明应力路径对钙质砂的抗剪强度和变形特征具有重要影响。钙质砂在等向压缩条件下具有明显的各向异性特征;常规三轴压缩试验条件下,密实钙质砂呈现低压剪胀、高压剪缩的变形特征,且峰值强度与初始固结压力之间呈幂函数关系;平均主应力为常数的三轴压缩试验中,增加偏应力会引起试样的体变;与常规三轴压缩试验不同,在减压的三轴压缩试验中,应力-应变关系曲线均表现为应变软化;而等应力比加载试验中,试样基本处于弹性状态下,且轴向应力与轴向应变之间呈幂函数关系。试验结果还发现钙质砂的切线泊松比不仅要考虑钙质砂的变形和应力状态等的影响,还要考虑应力路径的影响。不同应力路径试验条件下峰值应力比大小顺序与最大体变大小顺序不受初始固结压力的影响。钙质砂的峰值内摩擦角均随着初始固结压力的增大而减小,大致与初始固结压力的对数呈线性函数关系。 相似文献
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沉积岩的一种各向异性模型 总被引：1，自引：0，他引：1
给出了沉积岩的一种各向异性模型。用一个各向异性参数描述这类材料的固有各向异性，各向异性参数和单轴抗压强度是一个分布函数，其分布用一个微结构张量和加载方向表示。建立了一个描述各向异性沉积岩变形过程的全塑性模型。用该模型对这一些三轴试验进行了模拟，结果表明该模型能有效地描述沉积岩的固有各向异性。 相似文献
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《岩土力学》2017,(Z2):123-130
采用卸载状态岩石的力学参数和相应的强度准则,描述卸荷岩体的力学性质可能存在一些不足之处。为了能够从理论上更准确地分析卸荷岩体的力学性质,从弹性应变能出发对卸荷岩体力学性质的演化进行了探讨,研究了岩体的开挖卸荷与卸荷试验中试样初始损伤程度的不同之处和弹性应变能、应力偏量第二不变量、应力张量第二不变量和泊松比内在关系,简要地分析了现有强度准则在描述卸荷岩体力学性质方面的不足之处。以弹性应变能为基础采用加载状态的岩石力学参数,对岩石的卸荷力学特性进行了理论分析与试验验证。结果表明,现有的大多数强度准则难以描述试样卸荷破坏时强度特征,且可能存在不满足能量守恒定律的情况;基于弹性应变能强度准则既可得到表征卸荷破坏时岩石的强度提高,又可以描述强度的减小。文中分析了产生上述结果的本质机理。 相似文献
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Jun-Mo Kim 《Mathematical Geology》2005,37(8):929-941
On the basis of vectorial formulation, a series of relatively simple closed-form mathematical equations is presented to determine
the direction cosines of the local coordinate axes associated with planar and linear structures in an anisotropic geologic
material from their geologic angle measurements (i.e., strike and dip for planar structures and trend and plunge for linear
structures). The equations are then applied to calculation of global anisotropic hydraulic conductivity and elastic stiffness
tensors with respect to the geographical coordinate axes from their local counterparts with respect to the material symmetry
axes. 相似文献
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The formulation of viscoelastic solutions from elastic equations using the ‘correspondence principle’ and an inverse Laplace transform has been discussed extensively in the literature. Because this method has been developed, many time-dependent solutions can be obtained from closed form elastic solutions and conditions have been delineated in which the ‘quasi-elastic’ approximation of the viscoelastic solution is within acceptable tolerance. This communication shows the feasibility of the application of these methods to formulate approximate nonlinear viscoelastic solutions with nonlinear stress-strain materials, and for want of a specific nonlinear model to demonstrate this, the hyperbolic model was selected. The ‘power law’ is used to model the relaxation modulus of the viscoelastic materials. There are five related development that are discussed here using a simple numerical example to illustrate each of them and they are: (1) a linear elastic solution, (2) a linear viscoelastic solution, (3) a nonlinear elastic solution, (4) a nonlinear viscoelastic solution and finally, (5) a ‘regression’ approximation of the nonlinear viscoelastic solution which is suggested by the series form of the elastic solution. All of these are related to one another and each provides an acceptably accurate solution of the problem it addresses. The latter is of particular practical interest since it can be used to provide answers to problems involving nonlinear viscoelastic materials while requiring only very small calculation times. The problem used as an example is the calculation of the displacement of a circular hole in an infinite plate made of a material with a nonlinear time-dependent stress-strain relationship. The nonlinear elastic form of the solution was developed by matching results from nonlinear finite element analysis. 相似文献
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Schistous rock can be considered—in a first approximation—as cross‐anisotropic linear elastic material. The determination of the corresponding material constants on the basis of the laboratory investigation of rock samples often fails, as the extraction of appropriate cores proves to be unfeasible (the cores disintegrate if the schistosity is pronounced). In this paper a new method is presented to determine the material constants of a linear elastic cross‐anisotropic rock on the basis of cavity expansion field tests, e.g. with a radial jack. To this purpose, an analytic approximation for the deformation of a hydrostatically loaded cylindrical cavity in cross‐anisotropic rock is derived which serves to the inverse analysis of the material parameters. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Neetu Garg 《Journal of Earth System Science》2009,118(6):677-687
In a pre-stressed anisotropic elastic medium, three types of quasi-waves propagate along an arbitrary direction. In general, none of the waves is truly longitudinal. The present study finds the specific directions in a pre-stressed anisotropic elastic medium along which longitudinal waves may propagate. This paper demonstrates how the propagation of longitudinal waves is affected by various pre-stresses present in the medium. The study establishes the explicit expressions defining the existence and propagation of longitudinal waves in pre-stressed anisotropic elastic medium. These expressions involve not only the direction and elastic stiffness of the medium, but also the pre-stresses present in the medium. Changes in conditions for the existence of longitudinal waves in orthotropic, monoclinic and triclinic anisotropies are discussed in detail. The most important part of the paper is a practical aspect suggested to calculate the specific directions for the existence of longitudinal waves in pre-stressed anisotropic elastic medium. In this approach, only those parameters are used that can be observed by the receiver in a geophysical experiment of wave propagation. The existence of longitudinal waves has been shown graphically using a numerical example for three types of anisotropic symmetries in elastic medium. 相似文献
15.
宜兴抽水蓄能电站试验洞的反分析研究 总被引：4，自引：2，他引：4
结合江苏宜兴抽水蓄能电站地下厂房试验洞量测资料的分析,研究了成层各向异性岩体中洞室工程问题的反分析方法。采用分层均质模型进行反分析计算。计算区域的各层岩层均被分别视为均质各向同性体,初始地应力假设呈线性分布。有限元分析中,对倾斜成层的岩层、软弱夹层及断层节理等分别划分了单元,据以模拟成层岩体的各向异性特征。为使计算过程简化,对离洞室较远的岩层拟按地质资料对材料特性参数赋值,反分析计算的目标未知数为初始地应力和试验洞相邻围岩的弹性模量。结果表明,与工程实践符合较好。 相似文献
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无黏性土的应力-应变关系可以用Gudehus-Bauer亚塑性本构模型来模拟,该模型强调应力增量的大小和方向不仅与当前应力状态有关,而且还取决于当前应变增量的大小和方向。为分析其与传统弹塑性理论的不同之处,对Gudehus-Bauer理论的线性项和非线性项进行了研究,并对不同初始孔隙比下Gudehus-Bauer亚塑性模型的应力-应变关系进行了探讨。结果表明Gudehus-Bauer亚塑性模型不用把应变分为弹性和塑性部分就能考虑不可逆变形,并能体现密砂的剪胀特性和应变软化特性以及松砂的剪缩特性和应变硬化特性。 相似文献
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A matrix relating stress and elastic strain tensors for anisotropic particulate materials has been derived. The magnitude of the matrix depends on the state of the material anisotropy. Anisotropy in granular materials depends on strain because normal and tangential particle contact forces, as well as the spatial distribution of the contacts, vary with stress and strain. However, the rotation tensor and the strain tensor cannot be independent; they must satisfy certain constraints to meet the requirement for macroscopic stress tensor symmetry. These conditions and constraints lead to the derivation of the matrix presented in this article. The principal directions of the stress tensor and strain tensor are generally not coincident, and the values of deformation parameters, Young's modulus and Poisson's ratio, are direction dependent; these two aspects are also discussed in this paper. Whereas this matrix can be used in static numerical analyses for elastic problems, we note that this relationship can also be used as a basis upon which to derive a fully incremental stress–strain relationship for anisotropic granular materials in the plastic state, where the anisotropy is evolving with strain. 相似文献
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基于复合材料以及连续介质损伤理论,给出了岩石材料的各向异性损伤破坏模型。通过引入与岩石材料单轴加载行为相对应的特征模态构成的四阶对称损伤张量,描述了岩石材料的损伤演化过程,其中对不同主应变方向采用不同的损伤变量,而对同一主应变方向拉压时的损伤则采用不同的损伤变量来描述。在数值模拟岩石破坏过程的程序中,采用了张量分解的方法。将该模型编写用户材料子程序,并嵌入到大型有限元分析程序ABAQUS中,通过ABAQUS/EXPLICIT SOLVER的显式有限元算法求解。利用此程序对岩石材料的单轴压缩进行了数值模拟。 相似文献
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建立尾砂的本构模型是开展尾矿坝数值模拟和安全评价的重要基础,而目前尾砂的本构模型研究多集中于非线性弹性模型,如Duncan-Chang模型,关于弹塑性模型的研究较少。结合尾砂的应力-应变特性,提出了一种适用于描述尾砂力学特性的改进广义塑性模型。基于用户自定义材料子程序UMAT,将提出的模型在ABAQUS中二次开发实现,应力积分采用Runge-Kutta显式积分。通过三轴试验模拟验证,偏差应力曲线表明,有限元计算结果可以反映围压对应力-应变关系的影响,抗剪强度随应变逐渐硬化,达到峰值强度,随后发生应变软化,抗剪强度有所下降。体应变曲线结果表明,广义塑性模型可以很好地描述体应变曲线的体缩-体胀发展过程,与试验曲线吻合较好。同时有限元数值模拟结果和理论值误差很小,且和试验结果拟合较好。该研究成果可进一步用于尾矿坝的应力变形计算和安全评价。 相似文献