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Clayey rocks are frequently chosen as a geological barrier material for underground repositories. The inherent anisotropic mechanical behavior and the evolution of mechanical behavior with water content are two crucial material properties for the safety analysis of these structures. The present paper focuses on numerical modeling of the inherent anisotropy and the effect of water content, as well as the interactions of these properties in partially saturated clayey rocks with preferably oriented bedding planes. A discrete thermodynamic approach is adopted for describing the inherent anisotropic mechanical behavior, and the anisotropy of the elastic parameters, plastic evolution and damage evolution are considered. Capillary pressure is introduced to describe the effect of the water content with the help of the effective stress concept, and a procedure for the identification of the model parameters is presented. Finally, the proposed model is applied to a study of triaxial compression tests of argillite with different orientations of the bedding planes and variable water content. In summary, the main features of the studied material are well reproduced by the model. 相似文献
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An underground research laboratory (URL) is being constructed by Andra in eastern France, in Callovo-Oxfordian claystone (COx) in which various in situ geomechanical experiments are being undertaken or are to be carried out. The aim of this URL is to characterize the in situ properties of COx claystone and to test disposal technologies in a realistic way in order to assess the short- and long-term safety of a deep radioactive waste repository. In parallel, theoretical and numerical models able to reproduce the phenomena observed under different types of loading paths must be developed.The phenomenological elastic-visco-plastic model developed by Souley et al. (2011) has been enhanced to reflect recent advances in understanding of the mechanical and hydromechanical behavior of COx claystone and the modification of the mechanical and hydraulic properties in the EDZ (Excavation Damage Zone). In particular, the influence of induced damage and fracturing on the delayed strains and strain rates of the COx claystone and the permeability changes observed at the site scale, as well as hydro-mechanical couplings, are discussed and incorporated in a new model. This model is implemented into the commercial code FLAC3D. Short- and long-term test data (Armand et al., 2016) can be used to identify possible key parameters for the model. These tests were also used to identify certain parameters of our model. Some tests were simulated to verify the numerical implementation of the proposed model.Finally, the simulation of the GCS drift excavation (Seyedi et al., 2016) has been performed. Comparisons to in situ measurements are discussed and some accordance and discrepancies were observed. 相似文献
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A micro-mechanics-based elastic–plastic model is proposed to describe mechanical behaviors of porous rock-like materials. The porous rock is considered as a composite material composed of a solid matrix and spherical pores. The effective elastic properties are determined from the classical Mori–Tanaka linear homogenization scheme. The solid matrix verifies a pressure-dependent Mises–Schleicher-type yield criterion. Based on the analytical macroscopic yield criterion previously determined with a nonlinear homogenization procedure (Shen et al. in Eur J Mech A/Solids 49:531–538, 2015), a complete elastic–plastic model is formulated with the determination of a specific plastic hardening law and plastic potential. The micro-mechanics-based elastic–plastic model is then implemented for a material point in view of simulations of homogeneous laboratory tests. The proposed model is applied to describe mechanical behaviors of two representative porous rocks, sandstone and chalk. Comparisons between numerical results and experimental data are presented for triaxial compression tests with different confining pressures, and they show that the micro-mechanical model is able to capture main features of mechanical behaviors of porous rock-like rocks. 相似文献
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A new phenomenological macroscopic constitutive model for the numerical simulation of quasi‐brittle fracture and ductile concrete behavior, under general triaxial stress conditions, is presented. The model is particularly addressed to simulate a wide range of confinement stress states, as also, to capture the strong influence of the mean stress value in the concrete failure mechanisms. The model is based on a two‐surface damage‐plastic formulation. The mechanical behavior in different domains of the stress space is separately described by means of a quasi‐brittle or ductile material response:
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非饱和土水-力本构模型及其隐式积分算法 总被引：1，自引：0，他引：1
在已有工作基础上建立了水力-力学耦合的非饱和土本构模型,在硬化方程中考虑饱和度的影响,同时在土水特征曲线中考虑了塑性体变的影响,从而使模型可以反映非饱和土中的毛细现象与土中弹塑性变形现象的耦合行为。采用隐式积分方法,建立了非饱和土耦合模型的数值模型,并推导了得到了水力-力学耦合的非饱和土的一致切线模量。利用该算法编制了本构模型计算的子程序,使其能向外输出切线刚度矩阵,用于有限元计算。为了验证该算法和程序的正确性,用所编制程序对不同路径下的土体行为进行了预测。通过预测结果与试验结果相对比,表明程序预测结果与试验数据相吻合,模型可以较好地模拟土体的水力-力学耦合行为特性。 相似文献
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In this paper a new finite element formulation for numerical analysis of diffused and localized failure behavior of saturated and partially saturated gradient poroplastic materials is proposed. The new finite element includes interpolation functions of first order (C1) for the internal variables field while classical C0 interpolation functions for the kinematic fields and pore pressure. This finite element formulation is compatible with a thermodynamically consistent gradient poroplastic theory previously proposed by the authors. In this material theory the internal variables are the only ones of non-local character. To verify the numerical efficiency of the proposed finite element formulation, the non-local gradient poroplastic constitutive theory is combined with the modified Cam Clay model for partially saturated continua. Thereby, the volumetric strain of the solid skeleton and the plastic porosity are the internal variables of the constitutive theory. The numerical results in this paper demonstrate the capabilities of the proposed finite element formulation to capture diffuse and localized failure modes of boundary value problems of porous media, depending on the acting confining pressure and on the material saturation degree. 相似文献
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To enhance the understanding of thermal impact on the in situ behaviour of the Callovo–Oxfordian argillite, this paper presents an interpretation of an in situ heating experiment carried out in the Meuse/Haute Marne Underground Research Laboratory (M/HM URL). The argillite was heated successively by two constant heating powers: 277 W and 925 W. When subjected to thermal loading, the argillite exhibits an important volume change and a strong pore pressure response that significantly affect its hydraulic and mechanical behaviour. Numerical analysis has been performed by using a coupled theoretical formulation that incorporates a constitutive model especially developed for this material. Based on Biot's theory, this model includes the influence of interstitial pressure on the mechanical behaviour. The simulation obtained reproduces satisfactorily the results of the in situ experiment and the main observed patterns of behaviour. The interpretation and discussion of numerical results provide additional data that can help us to understand the thermo-hydromechanical behaviour concepts of saturated argillite formation. 相似文献
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When evaluating the long-term stability of existing tunnels, the creep behavior of soft rock around the tunnel should be properly considered. It is also important to understand the failure mechanism of soft rock when designing the mitigation and remediation of the failure around a tunnel. In this paper, an elasto-viscoplastic model is first modified so that the overconsolidation effect and the structure effect of soft rock can be considered. Then, the performance of the modified model is confirmed with drained triaxial compression tests and creep tests on a manmade rock produced with gypsum and diatom clay. Based on the modified model, finite element analyses are conducted to simulate the model tests of an existing tunnel constructed within manmade rock. Two kinds of model tests are simulated: one is loading failure test and the other creep failure test. The good agreement between the numerical results and the test data validates the performance of the modified constitutive model and the applicability of the corresponding FEM for evaluating the creep failure behavior of an existed tunnel constructed in soft rock. 相似文献
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通过将Perzyna过应力理论与临界状态理论相结合,并引入Wheeler旋转硬化法则,提出一个能描述土体初始各向异性及应力诱发各向异性的三维弹黏塑性本构模型。模型考虑流变发生的下限,在三维应力空间,模型存在形状相似的静屈服面及动态加载面。采用缩放形式的幂函数。本构模型数值算法采用回映算法,借助ABAQUS软件UMAT子程序接口实现。并通过对三轴不排水蠕变试验的模拟,确定合适的积分步长。此后,分别对三轴不排水蠕变试验及常应变率三轴不排水剪切试验进行了模拟。模拟中通过设置不同参数值,可将模型退化为各向同性模型,并对这两种模拟结果进行了比较。模拟结果表明：(1) 对于三轴不排水蠕变,在低剪应力水平下,各向同性模型和各向异性模型模拟的结果相差不大,而在高剪应力水平下,各向异性模型模拟结果更接近试验结果;(2) 对于常应变率加载试验的模拟,模型合理反映了土体不排水强度随着加载速率的增大而增大现象。 相似文献
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A hierarchical thermo‐hydro‐plastic constitutive model for unsaturated soils and its numerical implementation 
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下载免费PDF全文 《国际地质力学数值与分析法杂志》2018,42(15):1785-1805
Unsaturated soils are highly heterogeneous 3‐phase porous media. Variations of temperature, the degree of saturation, and density have dramatic impacts on the hydro‐mechanical behavior of unsaturated soils. To model all these features, we present a thermo‐hydro‐plastic model in which the hydro‐mechanical hardening and thermal softening are incorporated in a hierarchical fashion for unsaturated soils. This novel constitutive model can capture heterogeneities in density, suction, the degree of saturation, and temperature. Specifically, this constitutive model has 2 ingredients: (1) it has a “mesoscale” mechanical state variable—porosity and 3 environmental state variables—suction, the degree of saturation, and temperature; (2) both temperature and mechanical effects on water retention properties are taken into account. The return mapping algorithm is applied to implement this model at Gauss point assuming an infinitesimal strain. At each time step, the return mapping is conducted only in principal elastic strain space, assuming no return mapping in suction and temperature. The numerical results obtained by this constitutive model are compared with the experimental results. It shows that the proposed model can simulate the thermo‐hydro‐mechanical behavior of unsaturated soils with satisfaction. We also conduct shear band analysis of an unsaturated soil specimen under plane strain condition to demonstrate the impact of temperature variation on shear banding triggered by initial material heterogeneities. 相似文献
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Diansen Yang Serge Chanchole Pierre Valli Liufeng Chen 《Rock Mechanics and Rock Engineering》2013,46(2):247-257
Due to various factors, such as sedimentation, layered morphology of clay minerals, in situ stress, etc., argillite rocks often exhibit anisotropic behavior. In order to study the anisotropic properties of the Callovo-Oxfordian (COx) argillite of the Meuse–Haute-Marne site in France considered as a possible host rock for high-level radioactive nuclear waste repository, a series of tests including uniaxial compression and dehydration and hydration at different constant applied stress levels are carried out. In this study, a specific setup combining moisture and mechanical loading with optical observation is used and it allows to continuously capture surface images from which the full-field strains are determined by using Digital Image Correlation techniques. The results show evidence of the mechanical and hydric anisotropy of the material. The anisotropy parameters are identified, assuming the studied argillite as transversely isotropic. The shrinkage and swelling depend on the applied stress and the angle with respect to the vertical direction of the mechanical load and the stratification plane, and this dependence is quantified. The non-linearity and the hysteresis observed during dehydration and hydration cycles are discussed. 相似文献
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基于广义位势理论建立的岩土体材料本构模型以及岩土体材料与结构接触面本构模型原理相通,只是前者是在三轴剪切试验条件下的三维应力空间建模,后者是在单剪试验条件下的二维应力空间建模。单剪试验条件下土与结构的接触面问题可以看作是法向与切向应力空间上的二维问题,其试验结果可以表达成由应力、应变组成的二维矢量。结合接触面力学特性,确定应力空间中的势函数以及塑性状态方程,可以推导出双重势面接触面弹塑性本构方程的一般表达式。进一步取两个势函数分别为法向应力和切向应力,建立简化双重势面接触面弹塑性模型的本构方程,该方程可直接应用于有限元等数值分析。结合试验实例对建模方法的合理性进行验证,模型拟合效果良好。研究结果表明,基于广义塑性位势理论建立接触面本构模型无需推求塑性势函数和屈服函数,可以直接得到弹塑性刚度矩阵,且建模方便。 相似文献
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岩盐弹塑性损伤耦合模型研究 总被引：5，自引：1，他引：4
岩盐力学模型是进行能源岩盐储存工程稳定性分析的基础,而损伤和塑性机制并存且相互耦合是岩盐力学行为的基本特点。采用云应岩盐,进行了多组围压条件下的三轴压缩试验,分析了不同围压下岩盐的变形特征。在试验分析的基础上,提出了一种能够描述岩盐特性的弹塑性损伤耦合的模型,该模型描述了岩盐损伤的演化和塑性变形的耦合关系,并引入了一种非关联的塑性流动法则来描述岩盐从塑性体积压缩到膨胀的转化。采用该模型对在三轴压缩下的岩盐应力-应变关系进行了模拟分析,并与试验数据进行了对比,结果表明该模型能够较好地描述岩盐的主要力学和变形特性。 相似文献
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Qingli Dai 《国际地质力学数值与分析法杂志》2010,34(13):1321-1345
This paper presents parallel and serial viscoelasto‐plastic models to simulate the rate‐independent and the rate‐dependent permanent deformation of stone‐based materials, respectively. The generalized Maxwell viscoelastic and Chaboche's plastic models were employed to formulate the proposed parallel and serial viscoelasto‐plastic constitutive laws. The finite element (FE) implementation of the parallel model used a displacement‐based incremental formulation for the viscoelastic part and an elastic predictor—plastic corrector scheme for the elastoplastic component. The FE framework of the serial viscoelasto‐plastic model employed a viscoelastic predictor—plastic corrector algorithm. The stone‐based materials are consisted of irregular aggregates, matrix and air voids. This study used asphalt mixtures as an example. A digital sample was generated with imaging analysis from an optically scanned surface image of an asphalt mixture specimen. The modeling scheme employed continuum elements to mesh the effective matrix, and rigid bodies for aggregates. The ABAQUS user material subroutines defined with the proposed viscoelasto‐plastic matrix models were employed. The micromechanical FE simulations were conducted on the digital mixture sample with the viscoelasto‐plastic matrix models. The simulation results showed that the serial viscoelasto‐plastic matrix model generated more permanent deformation than the parallel one by using the identical material parameters and displacement loadings. The effect of loading rates on the material viscoelastic and viscoelasto‐plastic mixture behaviors was investigated. Permanent deformations under cyclic loadings were determined with FE simulations. The comparison studies showed that the simulation results correctly predicted the rate‐independent and rate‐dependent viscoelasto‐plastic constitutive properties of the proposed matrix models. Overall, these studies indicated that the developed micromechanical FE models have the abilities to predict the global viscoelasto‐plastic behaviors of the stone‐based materials. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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上海第4层黏土是典型的结构性海相软土,用一个本构模型统一地模拟不同应力路径下的力学特性对数值计算具有重要意义。对UNIFIED模型的结构性及超固结发展函数进行了改进,并提出了一种确定原状土材料参数和初始状态的方法。为了验证修正模型的正确性,用块状取土法取得上海第4层原状土样,进行了固结试验和三轴排水、不排水剪切试验。通过比较试验结果和本构模拟结果,明确了新的本构模型仅用一组材料参数就能统一地模拟上海第4层黏土在固结、排水及不排水三轴试验得到的应力-应变关系。模拟结果揭示了上海第4层黏土的结构比较稳定,即使在经历三轴剪切发生35%轴应变后仍能保持较高位的结构性。 相似文献