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岩石损伤过程中的热-流-力耦合模型及其应用初探 总被引：3，自引：0，他引：3
岩石损伤过程热-流-力（THM）耦合问题的研究对于深部采矿等许多工程领域都具有重要的理论意义。以岩石的损伤为主线,在多场耦合分析方程中引入损伤变量,基于质量守恒和能量守恒原理,提出岩体损伤过程中的THM耦合模型。通过把均匀弹性介质THM耦合响应的模拟结果与理论分析结果进行对比,验证了程序及有限元实施的正确性。然后,用该耦合模型进行了不同地应力条件下流固耦合过程的数值模拟,探讨了水压力对于岩石损伤过程的作用机制。数值模拟表明,水压力导致了拉伸损伤范围的扩大和损伤程度的加剧,同时亦对剪切损伤具有抑制作用。 相似文献
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We present a numerical modelling of elastoplastic damage due to drying shrinkage of concrete in the framework of mechanics of partially saturated porous media. An elastoplastic model coupled with isotropic damage is first formulated. Two plastic flow mechanisms are involved, controlled by applied stress and suction, respectively. A general concept of net effective stress is used in take into account effects of capillary pressure and material damage on stress‐controlled plastic deformation. Damage evolution depends both on elastic and plastic strains. The model's parameters are determined or chosen from relevant experimental data. Comparisons between numerical simulations and experimental data are presented to show the capacity of model to reproduce mains features of concrete behaviour under mechanical loading and during drying shrinkage of concrete. An example of application concerning drying of a concrete wall is finally presented. The results obtained allow to show potential capacity of proposed model for numerical modelling of complex coupling processes in concrete structures. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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Micromechanical approach to effective viscoelastic properties of micro‐fractured geomaterials 
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下载免费PDF全文 The aim of this paper is to formulate a micromechanics‐based approach to non‐aging viscoelastic behavior of materials with randomly distributed micro‐fractures. Unlike cracks, fractures are discontinuities that are able to transfer stresses and can therefore be regarded from a mechanical viewpoint as interfaces endowed with a specific behavior under normal and shear loading. Making use of the elastic‐viscoelastic correspondence principle together with a Mori‐Tanka homogenization scheme, the effective viscoelastic behavior is assessed from properties of the material constituents and damage parameters related to density and size of fractures. It is notably shown that the homogenized behavior thus formulated can be described in most cases by means of a generalized Maxwell rheological model. For practical implementation in structural analyses, an approximate model for the isotropic homogenized fractured medium is formulated within the class of Burger models. Although the approximation is basically developed for short‐term and long‐term behaviors, numerical applications indicate that the approximate Burger model accurately reproduce the homogenized viscoelastic behavior also in the transient conditions. 相似文献
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This modelling study deals with the time‐dependent behaviour of rockfill media, which is of particular interest during the life of rockfill dams. Breakage of rock blocks and crack propagation are the main processes responsible for rockfill creep and collapse. The modelling procedure presented here is performed on two scales: on the rock block scale, where the grain is taken to be an assembly of rigid particles initially endowed with cohesive bonds, and on the rockfill scale, which is taken to involve a set of breakable grains interacting via contact and friction processes. The grain breakage process is described in term of a thermodynamically consistent damage interface model, where the damage is a gradual delayed process. This model was implemented in a non‐smooth contact dynamics code. The effects of the main parameters involved were analysed by performing numerical studies. The ability of the model to predict the creep behaviour of rockfill media is confirmed by presenting several simulations. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Three‐dimensional simulations of tensile cracks in geomaterials by coupling meshless and finite element method 下载免费PDF全文
下载免费PDF全文 Failure in geotechnical engineering is often related to tension‐induced cracking in geomaterials. In this paper, a coupled meshless method and FEM is developed to analyze the problem of three‐dimensional cracking. The radial point interpolation method (RPIM) is used to model cracks in the smeared crack framework with an isotropic damage model. The identification of the meshless region is based on the stress state computed by FEM, and the adaptive coupling of RPIM and FEM is achieved by a direct algorithm. Mesh‐bias dependency, which poses difficulties in FEM‐based cracking simulations, is circumvented by a crack tracking algorithm. The performance of our scheme is demonstrated by two numerical examples, that is, the four‐point bending test on concrete beam and the surface cracks caused by tunnel excavation. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Large sets of soil experimental data (field and laboratory) are becoming increasingly available for calibration of soil constitutive models. A challenging task is to calibrate a potentially large number of model parameters to satisfactorily match many data sets simultaneously. This calibration effort can be facilitated by optimization techniques. The current study aims to explore systematic approaches for exercising optimization and sensitivity analysis in the area of soil constitutive modelling. Analytical, semi‐analytical and numerical optimization techniques are employed to calibrate a multi‐surface‐plasticity sand model. Calibration is based on results from a number of drained triaxial sample tests and a dynamic centrifuge liquefaction test. The analytical and semi‐analytical approaches and associated sensitivity analysis are applied to calibrate the model non‐linear shear stress–strain response. Thereafter, model parameters controlling shear–volume coupling effects (dilatancy) are calibrated using a solid–fluid fully coupled finite element program in conjunction with an advanced numerical optimization code. A related sensitivity study reveals the challenges often encountered in optimizing highly non‐linear functions. Overall, this study demonstrates applicability and limitations of optimization techniques for constitutive model calibration. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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The paper presents advances in the discrete element modelling of underground excavation processes extending modelling possibilities
as well as increasing computational efficiency. Efficient numerical models have been obtained using techniques of parallel
computing and coupling the discrete element method with finite element method. The discrete element algorithm has been applied
to simulation of different excavation processes, using different tools, TBMs and roadheaders. Numerical examples of tunnelling
process are included in the paper, showing results in the form of rock failure, damage in the material, cutting forces and
tool wear. Efficiency of the code for solving large scale geomechanical problems is also shown. 相似文献
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The deleterious effect of moisture in the microstructure of asphalt mixtures, usually referred to as moisture damage, has been recognized as a main cause of early deterioration of asphalt pavements. The initiation and evolution of moisture‐related deterioration is strongly influenced by the internal air void structure of asphalt mixtures. Despite its importance, the majority of works conducted on the micromechanical modeling of asphalt mixtures overlook the role of the air void structure, mainly because of its high complexity and variability. This paper explores the influence of air void variability on the performance of asphalt mixtures subjected to moisture diffusion processes. A stochastic modeling technique based on random field theory was used to generate internal distributions of physical and mechanical properties of the asphalt matrix of the mixture that depend on probable air voids distributions. The analysis was conducted by means of a coupled numerical micromechanical model of moisture damage. The results showed that the variability and distribution of air voids are decisive in determining the moisture‐dependent performance of asphalt mixtures. Furthermore, it was also shown that a stochastic characterization of the diverse air void configurations is a feasible and useful approach to better represent and understand mechanically related deterioration processes in asphalt mixtures. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Extension of plasticity theory to debonding,grain dissolution,and chemical damage of calcarenites 下载免费PDF全文
下载免费PDF全文 The mechanical properties of calcarenites are known to be significantly affected by water saturation: both stiffness and strength decrease for wetting in the short term and for chemical dissolution in the long term. Both processes mainly affect bonds among grains: immediately after inundation depositional bonds fall in suspension, whereas diagenetic bonds dissolve more slowly. In this paper, the authors started from the micro‐structural analysis of the weathering processes to conceive a strain hardening hydro‐chemo‐mechanical coupled elastoplastic constitutive model. The concept of extended hardening rules is here enriched: weathering functions have been determined by employing a micro to macro simplified upscaling procedure. Chemical damage is incorporated into the formulation by means of a scalar damage function. Its evolution is also described by using a multiscale approach. A new term is added to the strain rate tensor in order to incorporate the dissolution induced chemical deformations developing once the soft rock is turned into a granular material. A calibration procedure for the constitutive parameters is suggested, and the model is validated by using both coupled and uncoupled chemo‐mechanical experimental test results. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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在地下水渗流场、应力场、损伤场的耦合作用下更易造成隧道围岩坍塌或涌水等灾害。首先,将围岩材料视作各向同性连续介质,基于Drucker-Prager准则建立岩石弹塑性损伤本构模型,采用完全隐式返回映射算法实现弹塑性损伤本构方程的数值求解。其次,以上述研究为基础根据岩石处于弹塑性状态时渗透系数动态演化公式,建立岩石弹塑性应力-渗流-损伤耦合模型,并给出三场耦合情况下的数值求解迭代方法。针对耦合模型中涉及参数较多且不易测定的问题,基于差异进化算法原理建立智能反分析方法,对耦合模型中的损伤参数进行反演。最后,利用C++语言编制相应的岩石弹塑性应力-渗流-损伤耦合程序和参数反演程序,利用所编程序进行以下计算:(1)对智能反分析程序的性能、正确性进行分析,对比不同差异策略、交叉因子、变异因子的反演精度和收敛速度。(2)分别采用弹性模型和弹塑性损伤模型进行隧道围岩位移场、应力场的计算。(3)不考虑力学作用的情况下进行孔隙水压力、渗流量的计算。(4)采用所建耦合模型计算得到隧道围岩应力场、渗流场以及损伤场的相互影响规律。研究结果表明,基于差异进化算法的智能反分析程序能够较好地解决耦合模型中损伤参数不易确定的难题,为实际工程中获得不易测定的计算参数提供了有效的方法,同时所建立的耦合模型通过应力、渗流和损伤的相互作用更能够真实地反映出岩石材料的宏观破坏现象,所编计算程序能够模拟地下水渗流场、应力场、损伤场之间的耦合特性,为受地下水影响严重的工程建设提供了方法,研究结论为后期对实际隧道工程进行耦合计算奠定基础。 相似文献
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This paper deals with numerical modeling of the compressive behavior of granite rock under high strain rate dynamic loading and wide range of confining pressure. For this end, a constitutive model based on damage mechanics and viscoplasticity for rock is formulated and implemented in explicit dynamics FEM. The viscoplastic part is based on a simple power law type yield criterion that incorporates the rate-dependency with a linear viscosity term. Moreover, a Rankine type of tensile cut-off is employed. The damage part of the model is formulated with separate scalar damage variables in tension and compression. The model is calibrated for Kuru granite and validated with the experimental data from dynamic compression tests at the strain rate of 600 1/s up to 225 MPa of confining pressure. The numerical simulations demonstrate that, despite the underlying continuum modeling approach, the model captures the correct experimental failure modes, including the transition from single-to-multiple fragmentation, as well as the dynamic compressive strengths at different confining pressures. 相似文献
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Coupled hydro‐mechanical processes in granular media represent the interaction between solid particles movement and fluid flow during external and/or internal loading. The processes attract attention in geotechnical engineering since they cause many disasters such as landslide, slope collapse, boiling/quicksand and soil liquefaction, etc. This study presents a numerical method combining discontinuous deformation analysis (DDA) for mechanical calculation and finite element method for fluid flow simulation to model the interaction between solid particles' movement and fluid flow from microscopic point of view. The term of hydraulic pressure was newly formulated and introduced to the original DDA. The simplified examples are given to verify the new method, and the computational results correlate well with the theoretical calculations, further development is also considered. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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A two‐scale modeling of solute transport in double‐porosity (DP) media under unsaturated water flow conditions is presented. The macroscopic model was developed by applying the asymptotic homogenization method. It is based on theoretical and empirical considerations dealing with the orders of magnitude of characteristic quantities involved in the process. For this purpose a physical model that mimics the behavior of DP medium was built. The resulting two‐equation model relies on a coupling exchange term between micro‐ and macro‐porosity subdomains associated with local non‐equilibrium solute concentrations. The model was numerically implemented (Comsol Multiphysics®) to simulate the macroscopic one‐dimensional physical process taking place into the porous medium of 3D periodic microstructure. A series of dispersion experiments of NaCl solution under unsaturated steady‐state flow conditions were performed. The experimental results were used first to calibrate the dispersion coefficient of the model, and second to validate it through two other independent experiments. The excellent agreement between the numerical simulations and the measurements of the time evolution of the non‐symmetrical breakthrough curves provides a proof of predictive capacity of the developed model. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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For civil engineering structures with a tightness role, structural permeability is a key issue. In this context, this paper presents a new proposition of a numerical modelling of leakage rate through a cracked concrete structure undergoing mode I cracking. The mechanical state of the material, considered in the framework of continuum mechanics based on finite element modelling, is described by means of the stress‐based nonlocal damage model which takes into account the stress state and provides realistic local mechanical fields. A semi‐discrete method based on the strong discontinuity approach to estimate crack opening is then considered in the post‐treatment phase. Using a Poiseuille's like relation, the coupling between the mechanical state of the material and its dry gas conductivity is performed. For validation purposes, an original experimental campaign is conducted on a dry concrete disc loaded in a splitting setup. During the loading, gas conductivity and digital image correlation analysis are performed. The comparison with the 3D experimental mechanical global response highlights the performance of the mechanical model. The comparison between crack openings measured by digital image correlation and estimated by the strong discontinuity method shows a good agreement. Finally, the results of the semi‐discrete approach coupled with the gas conductivity compared with experimental data show a good estimation of the structural conductivity. Consequently, if the mechanical problem is well modelled at the global scale, then the proposed approach provides good estimation of gas conductivity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Damage‐viscoplastic consistency model for rock fracture in heterogeneous rocks under dynamic loading
Timo Saksala 《国际地质力学数值与分析法杂志》2010,34(10):1041-1062
This paper presents a damage‐viscoplastic consistency model for numerical simulation of brittle fracture in heterogeneous rocks. The model is based on a combination of the recent viscoplastic consistency model by Wang and the isotropic damage concept with separate damage variables in tension and compression. This approach does not suffer from ill‐posedness, caused by strain softening, of the underlying boundary/initial value problem since viscoplasticity provides the regularization by introducing a length scale effect under dynamic loading conditions. The model uses the Mohr–Coulomb yield criterion with the Rankine criterion as a tensile cut‐off. The damage law in compression is calibrated via the degradation index concept of Fang and Harrison. Thereby, the model is able to capture the brittle‐to‐ductile transition occurring in confined compression at a certain level of confinement. The heterogeneity of rock is accounted for by the statistical approach based on the Weibull distribution. Numerical simulations of confined compression test in plane strain conditions demonstrate a good agreement with the experiments at both the material point and structural levels as the fracture modes are realistically predicted. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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This paper establishes an anisotropic nonlinear damage model in strain space to describe the behavior of jointed rock and applies it to mechanical analysis of tunnelling. This work focuses on rate-independent and small-deformation behavior during static isothermal processes. The prime results include: (1) the properties of damage-dependent elasticity tensors based on geological information of the jointed rock mass; (2) the damage evolution law presented on the basis of thermodynamics and combined with endochronic theory; and (3) the global damage tensor based on the work-equivalence principle and the local geological data of multi-joint sets. Finally the numerical results of a tunnel intersection in jointed rock is presented to illustrate the mechanical behavior of this model. 相似文献
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On the failure of a discrete axial chain using a continualized nonlocal Continuum Damage Mechanics approach 下载免费PDF全文
下载免费PDF全文 The failure of a discrete elastic‐damage axial system is investigated using both a discrete and an equivalent continuum approach. The Discrete Damage Mechanics approach is based on a microstructured model composed of a series of periodic elastic‐damage springs (axial Discrete Damage Mechanics lattice system). Such a discrete damage system can be associated with the finite difference formulation of a Continuum Damage Mechanics evolution problem. Several analytical and numerical results are presented for the tensile failure of this axial damage chain under its own weight. The nonlocal Continuum Damage Mechanics models examined in this paper are mainly built from a continualization procedure applied to centered or uncentered finite difference schemes. The asymptotic expansion of the first‐order upward difference equations leads to a first‐order nonlocal model, whereas the asymptotic expansion of the centered finite difference equations leads to a second‐order nonlocal Eringen's approach. To complete this study, a phenomenological nonlocal gradient approach is also examined and compared with the first continualization methods. A comparison of the discrete and the continuous problems for the chains shows the effectiveness of the new micromechanics‐based nonlocal Continuum Damage modeling, especially for capturing scale effects. For both continualized approaches, the length scale of the nonlocal models depends only on the cell size, while for the so‐called phenomenological approach, the length scale may depend on the loading parameter. This apparent load‐dependent length scale, already discussed in the literature with numerical arguments, is found to be sensitive to the postulated structure of the nonlocal model calibrated according to a lattice approach. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献