共查询到20条相似文献，搜索用时 187 毫秒
1.
In this paper, a numerical model is developed for the fully coupled hydro‐mechanical analysis of deformable, progressively fracturing porous media interacting with the flow of two immiscible, compressible wetting and non‐wetting pore fluids, in which the coupling between various processes is taken into account. The governing equations involving the coupled solid skeleton deformation and two‐phase fluid flow in partially saturated porous media including cohesive cracks are derived within the framework of the generalized Biot theory. The fluid flow within the crack is simulated using the Darcy law in which the permeability variation with porosity because of the cracking of the solid skeleton is accounted. The cohesive crack model is integrated into the numerical modeling by means of which the nonlinear fracture processes occurring along the fracture process zone are simulated. The solid phase displacement, the wetting phase pressure and the capillary pressure are taken as the primary variables of the three‐phase formulation. The other variables are incorporated into the model via the experimentally determined functions, which specify the relationship between the hydraulic properties of the fracturing porous medium, that is saturation, permeability and capillary pressure. The spatial discretization is implemented by employing the extended finite element method, and the time domain discretization is performed using the generalized Newmark scheme to derive the final system of fully coupled nonlinear equations of the hydro‐mechanical problem. It is illustrated that by allowing for the interaction between various processes, that is the solid skeleton deformation, the wetting and the non‐wetting pore fluid flow and the cohesive crack propagation, the effect of the presence of the geomechanical discontinuity can be completely captured. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
2.
In this paper, the numerical manifold method (NMM) is extended to study wave propagation across rock masses. First, improvements to the system equations, contact treatment, and boundary conditions of the NMM are performed, where new system equations are derived based on the Newmark assumption of the space–time relationship, the edge‐to‐edge contact treatment is further developed for the NMM to handle stress wave propagation across discontinuities, and the viscous non‐reflection boundary condition is derived based on the energy minimisation principle. After the modification, numerical comparisons between the original and improved NMM are presented. The results show that the original system equations result in artificial numerical damping, which can be overcome by the Newmark system equations. Meanwhile, the original contact scheme suffers some calculation problems when modelling stress wave propagation across a discontinuity, which can be solved by the proposed edge‐to‐edge contact scheme. Subsequently, the influence of the mesh size and time step on the improved NMM for stress wave propagation is studied. Finally, 2D wave propagation is modelled, and the model's results are in good agreement with the analytical solution. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
3.
Frictional slip plane growth by localization detection and the extended finite element method (XFEM)
This paper is concerned with developing a numerical tool for detecting instabilities in elasto‐plastic solids (with an emphasis on soils) and inserting a discontinuity at these instabilities allowing the boundary value problem to proceed beyond these instabilities. This consists of implementing an algorithm for detection of strong discontinuities within a finite element (FE) framework. These discontinuities are then inserted into the FE problem through the use of a displacement field enrichment technique called the extended finite element method (XFEM). The newly formed discontinuities are governed by a Mohr–Coulomb frictional law that is enforced by a penalty method. This implementation within an FE framework is then tested on a compressive soil block and a soil slope where the discontinuity is inserted and grown according to the localization detection. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
Mohammad Reza Maleki Javan 《国际地质力学数值与分析法杂志》2015,39(3):229-250
It is well known that for a sufficiently high seepage velocity, the governing flow law of porous media is nonlinear (J. Computers & Fluids 2010; 39 : 2069–2077). However, this fact has not been considered in the studies of soil‐pore fluid interaction and in conventional soil mechanics. In the present paper, a fully explicit dynamic finite element method is developed for nonlinear Darcy law. The governing equations are expressed for saturated porous media based on the extension of the Biot (J. Appl. Phys. 1941; 12 : 155–164) formulation. The elastoplastic behavior of soil under earthquake loading is simulated using a generalized plasticity theory that is composed of a yield surface along with non‐associated flow rule. Numerical simulations of porous media subjected to horizontal and vertical components of ground motion excitations with different permeability coefficients are carried out; while computed maximum pore water pressure is specially taken into consideration to make the difference between Darcy and non‐Darcy flow regimes tangible. Finally, the effect of non‐Darcy flow on the evaluated liquefaction potential of sand in comparison to conventional Darcy law is examined. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
5.
In this paper, the onset of mechanical instability in time‐sensitive elasto‐viscoplastic solids is theoretically analyzed at the constitutive level and associated with the occurrence of ‘spontaneous accelerations’ under stationary external perturbations. For this purpose, a second‐order form of Perzyna's constitutive equations is first derived by time differentiation, and a sufficient stability condition is identified for general mixed loading programs. These loading conditions are in fact the most general in both laboratory tests and real boundary value problems, where a combination of certain stress and strain components is known/prescribed. The theoretical analysis leads to find precise stability limits in terms of material hardening modulus. In the case of constitutive relationships with isotropic strain‐hardening, no instabilities are possible while the hardening modulus is larger than the so‐called ‘controllability modulus’ defined for (inviscid) elasto‐plastic materials. It is also shown that the current stress/strain rate may also directly influence the occurrence of elasto‐viscoplastic instability, which is at variance with elasto‐plastic inviscid media. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
We investigate shear band initiation and propagation in fully saturated porous media by means of a combination of strong discontinuities (discontinuities in the displacement field) and XFEM. As a constitutive behavior of the solid phase, a Drucker–Prager model is used within a framework of non-associated plasticity to account for dilation of the sample. Strong discontinuities circumvent the difficulties which appear when trying to model shear band formation in the context of classical nonlinear continuum mechanics and when trying to resolve them with classical numerical methods like the finite element method. XFEM, on the other hand, is well suited to deal with problems where a discontinuity propagates, without the need of remeshing. The numerical results are confirmed by the application of Hill’s second-order work criterion which allows to evaluate the material point instability not only locally but also for the whole domain. 相似文献
7.
The general forms for the field equations governing the transient response of poroelastic media given by Biot and by Zienkiewicz are compared and relations between the material constants are obtained. A one-dimensional analytical solution is presented for the situation where the solid and fluid materials satisfy Biot'S dynamic compatibility relation. The transient response of porous media is illustrated for varying degrees of solid and fluid compressibility when subjected to step, cyclic and short duration spike surface tractions. The results obtained (for the special situation where the materials are dynamically compatible) exhibit the overall characteristics of wave propagation in porous media and will provide representative test problems which allow a quantitative evaluation of the accuracy of various numerical solution methods (e.g. finite element models). 相似文献
8.
In this contribution an algorithm for parameter identification of geometrically linear Terzaghi–Biot‐type fluid‐saturated porous media is proposed, in which non‐uniform distributions of the state variables such as stresses, strains and fluid pore pressure are taken into account. To this end a least‐squares functional consisting of experimental data and simulated data is minimized, whereby the latter are obtained with the finite element method. This strategy allows parameter identification based on in situ experiments. In order to improve the efficiency of the minimization process, a gradient‐based optimization algorithm is applied, and therefore the corresponding sensitivity analysis for the coupled two‐phase problem is described in a systematic manner. For illustrative purpose, the performance of the algorithm is demonstrated for a slope stability problem, in which a quadratic Drucker–Prager plasticity model for the solid and a linear Darcy law for the fluid are combined. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
9.
In this paper, a series of multimaterial benchmark problems in saturated and partially saturated two‐phase and three‐phase deforming porous media are addressed. To solve the process of fluid flow in partially saturated porous media, a fully coupled three‐phase formulation is developed on the basis of available experimental relations for updating saturation and permeabilities during the analysis. The well‐known element free Galerkin mesh‐free method is adopted. The partition of unity property of MLS shape functions allows for the field variables to be extrinsically enriched by appropriate functions that introduce existing discontinuities in the solution field. Enrichment of the main unknowns including solid displacement, water phase pressure, and gas phase pressure are accounted for, and a suitable enrichment strategy for different discontinuity types are discussed. In the case of weak discontinuity, the enrichment technique previously used by Krongauz and Belytschko [Int. J. Numer. Meth. Engng., 1998; 41:1215–1233] is selected. As these functions possess discontinuity in their first derivatives, they can be used for modeling material interfaces, generating only minor oscillations in derivative fields (strain and pressure gradients for multiphase porous media), as opposed to unenriched and constrained mesh‐free methods. Different problems of multimaterial poro‐elasticity including fully saturated, partially saturated one, and two‐phase flows under the assumption of fully coupled extended formulation of Biot are examined. As a further development, problems involved with both material interface and impermeable discontinuities, where no fluid exchange is permitted across the discontinuity, are considered and numerically discussed. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
基于现有结构面剪切力学特性研究中对简单几何形态结构面研究多,天然形态结构面研究少,力学性质演化研究多,几何形态演化研究少的研究现状,通过巴西劈裂试验制备近天然形态岩石结构面,并采用模拟材料批量复制劈裂结构面试样的方法,开展循环荷载作用下岩石劈裂结构面的剪切力学特性演化规律与影响因素研究,分析法向应力、循环剪切次数、岩壁强度以及结构面粗糙度对循环剪切作用下岩体结构面力学特性和形貌特征的影响。最终通过在黏着摩擦理论-Barton经验公式中引入与循环剪切次数Nd有关的负指数假定劣化参数,提出了岩体结构面循环剪切强度公式。研究结果表明：法向应力、岩壁强度、结构面粗糙度越大,结构面的最大剪应力越大;法向应力、循环剪切次数、结构面粗糙度越大,岩壁强度越小,则归一化粗糙度参数越小。提出的循环剪切强度公式较好地验证了试验结果,可为工程安全设计提供理论参考。 相似文献
11.
In actual geotechnical and civil engineering, dynamic stress concentrations around cavities generated by wave sources widely exist. In this study, based on the complex variable theory and Fourier transform method, the expression of the dynamic stress concentration factor (DSCF) around a circular cavity in infinite homogeneous media subjected to transient waves with arbitrary waveform is obtained. The relationships between both steady-state and transient DSCF and their waveform parameters are investigated quantitatively. The results indicate that a relatively large tensile stress is generated with low Poisson's ratio under steady-state incidence. Under the condition of transient incidence, the position of the wave peak has a minor effect on the DSCF in the case of small wavenumber, but it has a significant effect in the opposite case. It is found that when the wavenumber is high, such as 0.5, the stress response lags behind the stress wave. In addition, the closer the wave peak to the center of the waveform, the greater the potential damage of the transient incidence. 相似文献
12.
Propagation of Rayleigh waves in fluid‐saturated non‐homogeneous soils with the graded solid skeleton distribution 
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下载免费PDF全文 The propagation characteristic of Rayleigh waves in a fluid‐saturated non‐homogeneous poroelastic half‐plane is addressed. Based on Biot's theory for fluid‐saturated media, which takes the inertia, fluid viscosity, mechanical coupling, compressibility of solid grains, and fluid into account, the dispersion equations of Rayleigh waves in fluid‐saturated non‐homogeneous soils/rocks are established. By considering the shear modulus of solid skeleton variation with depth exponentially, a small parameter, which reflects the relative change of shear modulus, is introduced. The asymptotic solution of the dispersion equation expressing the relationship between the phase velocity and wave number is obtained by using the perturbation method. In order to analyze the effects of non‐homogeneity on the propagation characteristic of Rayleigh waves, the variation of the phase velocity with the wave number is presented graphically and discussed through numerical examples. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
13.
Rock slope failure is a complex process that usually involves both opening/sliding along pre‐existing discontinuities as well as fracturing of intact rock bridges. Discontinuity persistence is an important factor governing rock slope instabilities. However, traditional slope failure analysis assumes persistent discontinuities, and rock slope fails along a predefined persistent continuous potential failure surface because of the limitations of the analysis tools. This paper proposes the numerical manifold method (NMM) incorporated with a Mohr–Coulomb criterion‐based fracturing algorithm to simulate the progressive failure of rock slopes with non‐persistent joints. Detailed fracturing algorithm is first presented. Then, the NMM enabling fracturing is calibrated through simulating an edge‐cracked plate and the Brazilian test. Lastly, the developed code is applied to investigate the failure process of rock slopes involving non‐persistent joints. Numerical results indicate that the proposed method can capture the opening/sliding along existing discontinuities, the fracturing in intact rock bridges and the final kinematic release. Progressive slope failure is well exhibited. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
14.
Behnam V. Damirchi Marcelo R. Carvalho Luís A. G. Bitencourt Osvaldo L. Manzoli Daniel Dias‐da‐Costa 《国际地质力学数值与分析法杂志》2021,45(1):83-107
A new discrete fracture model is introduced to simulate the steady‐state fluid flow in discontinuous porous media. The formulation uses a multi‐layered approach to capture the effect of both longitudinal and transverse permeability of the discontinuities in the pressure distribution. The formulation allows the independent discretisation of mesh and discontinuities, which do not need to conform. Given that the formulation is developed at the element level, no additional degrees of freedom or special integration procedures are required for coupling the non‐conforming meshes. The proposed model is shown to be reliable regardless of the permeability of the discontinuity being higher or lower than the surrounding domain. Four numerical examples of increasing complexity are solved to demonstrate the efficiency and accuracy of the new technique when compared with results available in the literature. Results show that the proposed method can simulate the fluid pressure distribution in fractured porous media. Furthermore, a sensitivity analysis demonstrated the stability regarding the condition number for wide range values of the coupling parameter. 相似文献
15.
Kenneth Runesson 《国际地质力学数值与分析法杂志》1987,11(3):315-321
The stress solution in plasticity with an associated or a non-associated flow rule is considered. Upon fully implicit integration of the relevant constitutive relations the stress is obtained as the projection of the (fictitious) elastic stress onto the yield surface for given values of the hardening softening variables. This projection is defined, for a general non-associated flow rule, in adjusted complementary elastic energy, which becomes exactly the complementary energy when the flow rule is associated. Isotropic elasticity and mean-stress dependent isotropic yield criteria (pertinent to soil) are considered and the implications of a certain class of non-associated flow rules are evaluated. This class relates to dilatant (or contractant) materials and involves non-associated plastic volume change. The corresponding stress solutions are shown to be strongly influenced by Poisson's ratio and by the dilation angle. 相似文献
16.
裂缝诱导双相HTI介质模型及其弹性波传播方程 总被引：1，自引：0，他引：1
将Biot双相介质理论与Gurevich裂缝各向异性理论相结合,建立了能够同时考虑实际裂缝性储层孔隙性和各向异性的裂缝诱导双相HTI介质模型。从本构方程、动力学方程和动力学达西定律出发,推导出了裂缝诱导双相HTI介质中弹性波传播的一阶速度-应力方程,并针对方程的刚性问题,给出了利用显式二阶时间积分法数值求解该方程时所需要满足的稳定性条件。该方程能够定量地给出双相HTI介质的波场特征与裂缝参数、背景孔隙介质参数之间的关系,描述弹性波在这种介质中的传播机理。 相似文献
17.
Interaction of a cylindrical thin‐walled pile with an inhomogeneous isotropic elastic medium 下载免费PDF全文
下载免费PDF全文 This paper presents a rigorous analysis for the static interaction of a cylindrical thin‐walled pile with an inhomogeneous isotropic elastic half‐space under vertical, horizontal, and torsional forces individually applied at the top of pile. The inhomogeneity is specified with the exponential variation of shear modulus along depth of the embedding medium, and the Poisson's ratio is assumed to be constant. By means of a set of Green's functions for pile and soil medium and satisfying the compatibility conditions between the 2 interacting media, the formulation is reduced to coupled Fredholm integral equations. Using the adaptive‐gradient elements, capable of capturing the singular stress transfer at both ends of the pile, a numerical procedure is developed and utilized for evaluating the relevant integral equations and studying the inhomogeneity effect on the soil‐pile interaction responses. The analysis results have been validated for different soil‐pile modulus ratios under axial load and for a Poisson's ratio of 0.3 under lateral load. The procedure does not consider the nonlinear behavior of the soil medium or plastic yielding in the pile section, and the impact of the unreliable results for the case of high Poisson's ratio is not examined. 相似文献
18.
Moche Ziv 《国际地质力学数值与分析法杂志》2002,26(4):373-406
First, the response of an ideal elastic half‐space to a line‐concentrated impulsive normal load applied to its surface is obtained by a computational method based on the theory of characteristics in conjunction with kinematical relations derived across surfaces of strong discontinuities. Then, the geometry is determined of the obtained waves and the source signature—the latter is the imprint of the spatiotemporal configuration of the excitation source in the resultant response. Behind the dilatational precursor wave, there exists a pencil of three plane waves extending from the vertex at the impingement point of the precursor wave on the stress‐free surface of the half‐space to three points located on the other two boundaries of the solution domain. These four wave‐arresting points (end points) of the three plane waves constitute the source signature. One wave is an inhibitor front in the behaviour of the normal stress components and the particle velocity, while in the behaviour of the shear stress component, it is a surface‐axis wave. The second is a surface wave in the behaviour of the horizontal components of the dependent variables, while the third is an inhibitor wave in the behaviour of the shear stress component. An inhibitor wave is so named, since beyond it, the material motion is dying or becomes uniform. A surface‐axis wave is so named, since upon its arrival, like a surface wave, the dependent variable in question features an extreme value, but unlike a surface wave, it exists in the entire depth of the solution domain. It is evident from this work that Saint‐Venant's principle for wave propagation problems cannot be formulated; therefore, the above results are a consequence of the particular model proposed here for the line‐concentrated normal load. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
19.
《Sedimentology》2018,65(2):360-399
Sedimentary gaps are a major obstacle in the reconstruction of a carbonate platform's history. In order to improve the understanding of the early diagenesis and the succession of events occurring during the formation of discontinuity surfaces in limestones, secondary ion mass spectrometry was used for the first time to measure the δ 18O and δ 13C signatures of 11 early cement and fabric stages in several discontinuity surfaces from the Jurassic carbonate platform of the Paris Basin, France. Pendant cements show a high variability in δ 18O, which was impossible to detect by the less precise microdrilling method. The morphology of a given cement can be produced in various environments, and dogtooth cements especially can precipitate in marine phreatic and meteoric phreatic to vadose environments. Marine dogtooth cements and micritic microbially induced fabrics precipitated directly as low‐magnesium calcite in marine waters, as attested to by the preservation of their initial δ 18O and δ 13C signals. Five discontinuity types are recognized based on high‐resolution geochemical analyses, and their palaeoenvironmental history can be reconstructed. Two exposure surfaces with non‐ferroan pendant or meniscus cements formed in the oxidizing vadose zone. A hardground displays marine fibrous cements and non‐ferroan dogtooth cements that formed in a subtidal environment in oxidizing water. Two composite surfaces have undergone both marine and subaerial lithification. Composite surface 1 displays non‐luminescent ferroan dogtooth cements that precipitated in reduced conditions in seawater, followed by brown‐luminescent dogtooth cements characteristic of a meteoric phreatic environment. Composite surface 2 exhibits microbially induced fabrics that formed in marine water with abundant organic matter. The latter discontinuity, initially formed in a subtidal environment, was subsequently exposed to meteoric conditions, as evidenced by ferroan geopetal cements. A high‐resolution ion microprobe study is essential to precisely document the successive diagenetic environments that have affected carbonate rocks and discontinuities with a polygenic and intricate history. 相似文献
20.
The fluid flow induced by an incident wave at a discontinuity separating two porous media is governed by the hydraulic permeabilities of both media and that of the interface. In the context of Biot’s theory, we derive the time-harmonic Green’s function for the two half-space problem allowing incident fast and slow dilatational waves to assess the heterogeneous modelling behaviour for diverse hydraulic conditions. It is found that when at least one of the media is permeated with inviscid fluids, heterogeneous modelling simulates open boundary conditions. On the other hand, when the model is saturated with viscous fluids, the modelling reproduces restrained fluid flow whose values correspond to sealed pore interface conditions, in agreement with the theoretical results. Therefore the numerical technique models correctly the wave diffusion and propagation phenomena attendant at the boundary. 相似文献