共查询到20条相似文献，搜索用时 156 毫秒
1.
In this paper, a multiphase three-dimensional numerical reproduction of a large-scale laboratory experiment of tsunami-like bore interaction with a surface-piercing circular column is presented. The numerical simulation is conducted using OpenFOAM. A dam-break mechanism is implemented in order to generate tsunami-like bores. The numerical model is validated using the results of experiments performed at the Canadian Hydraulics Center of the National Research Council in Ottawa, Canada. Unsteady Reynolds-Averaged Navier–Stokes equations are used in order to treat the turbulence effects. The Shear Stress Transport k–ω turbulence model showed a high level of accuracy in replicating the bore–structure interactions. A scaled-up domain is used to investigate the influence of bed condition in terms of various downstream depths and roughnesses. Finally, a broad investigation on bore propagation characteristics is performed. The stream-wise forces exerted on the structural column as well as the bore velocity are compared and analyzed for smooth, rough, dry and wet beds with varying depths.
相似文献2.
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:
3.
In this paper we consider the numerical solution of a coupled geomechanics and a stress-sensitive porous media reservoir flow
model. We combine mixed finite elements for Darcy flow and Galerkin finite elements for elasticity. This work focuses on deriving
convergence results for the numerical solution of this nonlinear partial differential system. We establish convergence with
respect to the L
2-norm for the pressure and for the average fluid velocity and with respect to the H
1-norm for the deformation. Estimates with respect to the L
2-norm for mean stress, which is of special importance since it is used in the computation of permeability for poro-elasticity,
can be derived using the estimates in the H
1-norm for the deformation. We start by deriving error estimates in a continuous-in-time setting. A cut-off operator is introduced
in the numerical scheme in order to derive convergence. The spatial grids for the discrete approximations of the pressure
and deformation do not need be the same. Theoretical convergence error estimates in a discrete-in-time setting are also derived
in the scope of this investigation. A numerical example supports the convergence results. 相似文献
4.
Dali Zhang Michael P. Lamoureux Gary F. Margrave Elena Cherkaev 《Computational Geosciences》2011,15(1):117-133
The article presents a numerical inversion method for estimation of quality Q factor and phase velocity in linear, viscoelastic, isotropic media using reconstruction of relaxation spectrum from measured
or computed complex velocity or modulus of the medium. Mathematically, the problem is formulated as an inverse problem for
reconstruction of relaxation spectrum in the analytic Stieltjes representation of the complex modulus using rational approximation.
A rational (Padé) approximation to the relaxation spec trum is derived from a constrained least squares minimization problem
with regularization. The recovered stress-strain relaxation spectrum is applied to numerical calculation of frequency-dependent
Q factor and frequency-dependent phase velocity for known analytical models of a standard linear viscoelastic solid (Zener)
model as well as a nearly constant-Q model which has a continuous spectrum. Numerical results for these analytic models show good agreement between theoretical
and predicted values and demonstrate the validity of the algorithm. The proposed method can be used for evaluating relaxation
mechanisms in seismic wavefield simulation of viscoelastic media. The constructed lower order Padé approximation can be used
for determination of the internal memory variables in time-domain finite difference numerical simulation of viscoelastic wave
propagation. 相似文献
5.
A non-linear optimization technique based on the quasi-Newton approach is employed to back-calculate certain model parameters of a simple, bounding surface, soil plasticity model from in situ pressuremeter data. The theoretical response corresponding to a given set of parameters is generated by finite element analysis. A semi-analytical procedure is developed for the accurate and efficient evaluation of the gradient of objective function with respect to the model parameters of interest. The BFGS update is used to update the Hessian. Results of a series of numerical experimentation using artificial pressuremeter responses is first reported and discussed. A set of laboratory cavity expansion data is then used to calibrate the constitutive model. 相似文献
6.
Discrete numerical modelling of rockfill dams 总被引：1，自引：0，他引：1
The aim of this study is to obtain quantitative information on the behaviour of rockfill used in embankment dams, and particularly on the influence of block breakage on the displacement field, from a numerical analysis using the Distinct element method. A methodology is set up to define the resistance of the 2D particles so that the same probability of breaking blocks may be reproduced as in a 3D material. The model uses the discrete element code PFC2D (Itasca Consulting Group Inc., PFC2D (Particle Flow Code in Two Dimensions), Version 3.0, 2002) and considers breakable clusters of 2D balls. The different parameters are determined from experimental data obtained from laboratory tests performed on rock blocks. The model is validated by comparing the results of the simulation of shearing tests with actual triaxial tests on rockfill material published in the literature. The numerical analysis of block crushing in an actual dam is proposed in the last part of this paper. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
7.
A numerical modelling approach is used to validate the physical and geological reliability of the ablative subduction mechanism during Alpine convergence in order to interpret the tectonic and metamorphic evolution of an inner portion of the Alpine belt: the Austroalpine Domain. The model predictions and the natural data for the Austroalpine of the Western Alps agree very well in terms of P–T peak conditions, relative chronology of peak and exhumation events, P–T–t paths, thermal gradients and the tectonic evolution of the continental rocks. These findings suggest that a pre‐collisional evolution of this domain, with the burial of the continental rocks (induced by ablative subduction of the overriding Adria plate) and their exhumation (driven by an upwelling flow generated in a hydrated mantle wedge) could be a valid mechanism that reproduces the actual tectono‐metamorphic configuration of this part of the Alps. There is less agreement between the model predictions and the natural data for the Austroalpine of the Central‐Eastern Alps. Based on the natural data available in the literature, a critical discussion of the other proposed mechanisms is presented, and additional geological factors that should be considered within the numerical model are suggested to improve the fitting to the numerical results; these factors include variations in the continental and/or oceanic thickness, variation of the subduction rate and/or slab dip, the initial thermal state of the passive margin, the occurrence of continental collision and an oblique convergence. 相似文献
8.
The mechanisms that govern porphyroblast crystallization are investigated by comparing quantitative textural data with predictions from different crystallization models. Such numerical models use kinetic formulations of the main crystallization mechanism to predict textural characteristics, such as grain size distributions. In turn, data on porphyroblast textures for natural samples are used to infer which mechanism dominated during their formation. Whereas previous models assume that the rate‐limiting step for a porphyroblast producing reaction is either transport or growth, the model advanced in this study considers the production of nutrients for porphyroblasts as a potentially rate‐limiting factor. This production reflects the breakdown of (metastable) reactants, which at a specific pressure (P) and temperature (T) depends on the bulk composition of the sample. The production of nutrients that potentially contribute to the formation of porphyroblasts is computed based on thermodynamic models. The conceptual model assumes that these nutrients feed into some intergranular medium, and products form by nutrient consumption from that medium, with rates depending on reaction affinity. For any sequence of P–T conditions along a P–T–t path, the numerical model first computes an effective supersaturation (σeff) of the product phase(s), then an effective nucleation rate (J), and finally the amount of (porphyroblast) growth. As a result, the model is useful in investigating how the textural characteristics of a sample (of given bulk composition) depend on the P–T–t path followed during porphyroblast crystallization. The numerical model is tested and validated by comparing simulation results with quantitative textural data for garnet porphyroblasts measured in samples from the Swiss Central Alps. 相似文献
9.
Earthquake-induced deformations for a bridge approach earth embankment are predicted using a calibrated numerical model. The
constitutive soil model is a modified hyperbolic model that uses Masing rules and incremental pore pressure relations. The
model was calibrated using both laboratory and field data. A shaking table physical model was used to verify the numerical
simulation. Additionally, the upper San Fernando dam was modeled to reproduce the deformations in the 1971 earthquake. The
subsurface and embankment soil conditions were characterized using field and laboratory methods. The model developed was used
to predict the earthquake-induced deformations of an approach embankment to Bridge A1466 in the NMSZ near Hayti, Missouri,
where strong earthquakes M > 7.0 are anticipated in the next 50 years. 相似文献
10.
The rotation behavior of rigid elliptical inclusions adherent to the viscous matrix in simple shear flow is investigated using a 2-D finite element numerical model. Several simulations were performed using different ratios (S) between shear zone width and inclusion's least principal axis. A computational strategy was devised to calculate pressure and viscous forces exerted on the inclusion and deduce its angular velocity. For large S values, results agree remarkably well with theoretical predictions, while for small S values results deviate significantly from theory but are in agreement with previous analogue experiments. The numerical model provided detailed and coherent information about the physical parameters involved in the process (e.g., pressure, strain rate and vorticity distributions within the model). 相似文献
11.
A design procedure is proposed to minimize water infiltration into landfills by optimizing the water diversion length of inclined
covers with capillary barrier effect (CCBE). This design procedure is based on a conceptual, mathematical and numerical approach
and aims at selecting materials and optimizing layer thickness. Selection among candidate materials is made based on their
hydraulic conductivity functions and on a threshold infiltration rate imposed on the designer. The capillary break layer (CBL;
bottom layer) is characterized by a weak capillarity, while the moisture retention layer (MRL; upper layer) is characterized
by a compromise between strong capillarity and high hydraulic conductivity. The thickness of the CBL corresponds to the height
where suction reaches its maximum value for a given infiltration rate. This height can be calculated using the Kisch [Géotechnique 9 (1959)] model. The optimal thickness of the MRL is determined by applying an adaptation of the Ross [Water Resources Research 26 (1990)] model. The results obtained using the proposed design procedure were compared to those obtained from numerical simulations
performed using a finite element unsaturated seepage software. The procedure was applied for two cover systems; one where
deinking by-products (DBP) were used as MRL and sand as CBL and another where sand was used as MRL and gravel as CBL. Using
this procedure, it has been shown that an infiltration control system composed of thin layers of sand over gravel is highly
efficient in terms of diversion length and that its efficiency can be enhanced by placing a hydraulic barrier – such as a
layer of DBP – above the MRL. 相似文献
12.
A self‐consistent approach for micro–macro modeling of elastic–plastic deformation in polycrystalline geomaterials 
下载免费PDF全文
下载免费PDF全文 This paper is devoted to multi‐scale modeling of elastic–plastic deformation of a class of geomaterials with a polycrystalline microstructure. We have extended and improved the simplified polycrystalline model presented in [Zeng T. et al., 2014. Mech. Mater. 69 (1):132–145]. A rigorous and fully consistent self‐consistent (SC) scheme is proposed to describe the interaction among plastic mineral grains. We have also deeply discussed the numerical issues related to the numerical implementation of the proposed micromechanical model. The efficiency of the proposed model and the related numerical procedure is evaluated in several representative cases. We have compared the numerical results respectively obtained from the fully SC model and two simplified ones. It is found that the SC model produces a softer stress–strain response than that of the simplified models. The comparisons between the estimation of overall behavior of a granite in different loading conditions and experimental data are also conducted. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
Determination of Shear Strength and Three-dimensional Yield Strength for the Hoek-Brown Criterion 总被引：1，自引：3，他引：1
S. D. Priest 《Rock Mechanics and Rock Engineering》2005,38(4):299-327
Summary. Most currently used techniques for analysing the stability of near surface structures, such as rock slopes, are based on the application of the effective Coulomb shear strength parameters cohesion c′, and the angle of friction φ′ on some known or anticipated shear surface subjected to an effective normal stress σ′n. The most widely used of these techniques are the variants of the method of slices and related upper bound techniques. If the Hoek-Brown criterion is to be used to model the strength of near surface fractured rocks, it is necessary to determine equivalent Coulomb shear strength parameters for the specified level of effective normal stress. Calculation of the equivalent Coulomb parameters for the Hoek-Brown criterion for cases when a ≠ 0.5 is not a straightforward matter. A simple procedure for calculating instantaneous values of c′i and φ′i has been developed based on spreadsheet calculations and the application of a numerical optimisation routine. This procedure can also be applied to calculating the Hoek-Brown envelope plotted in shear stress/normal stress space. A simple closed form solution for c′i and tan φ′i has also been developed for the special case when a = 1. A three-dimensional version of the Hoek-Brown criterion has been developed by combining it with the Drucker-Prager criterion. This new yield criterion has been implemented by numerical solution of the governing equations. A simplification of this three-dimensional yield criterion has been developed by introducing an intermediate principal stress weighting factor. Comparison with published results demonstrates that this simplified criterion has the capacity to model the results of true triaxial tests for a range of different rock types over a wide range of stress levels. The new three-dimensional yield criterion has the advantage that its input parameters can be determined from routine uniaxial compression tests and mineralogical examination. 相似文献
14.
Li-Ying Chang 《Geomechanics and Geoengineering》2018,13(3):159-167
The ranges of initial void ratios that can be achieved for numerical samples with the same grading as actual sand under gravity are explored using three-dimensional discrete element method (DEM). A corrected compressible accumulation model is proposed to predict the packing density of sand. Compared with the measured results, the errors of the prediction results are small. For three-dimensional DEM samples, when the ratio of sample size to particle size L/R is equal to or larger than 30, the maximum and the minimum void ratios are minimally affected by the sample size L. The maximum void ratios and the minimum void ratios of numerical samples with spherical particles are much smaller than those of actual sands. The generation method for numerical samples with non-spherical particles is proposed based on the theory of CPM. The variations of void ratios of numerical samples with non-spherical particles are wider than actual sands. So it can meet all the need of DEM simulation on the void ratio of actual sand. 相似文献
15.
Numerical investigation of the stabilisation behaviour of shallow foundations under alternate loading 总被引：1，自引：1，他引：0
Hendrik Sturm 《Acta Geotechnica》2009,4(4):283-292
This article presents a stability criterion for shallow foundations on sand for various loading conditions. By means of laboratory
model tests, a behaviour called self-healing is shown. Numerical simulations of these tests prove the suitability of the employed numerical model. Based on this validation,
a numerical parametric study is done to analyse the influence of loading condition and initial state of the soil on the self-healing. Main focus is on the rotational behaviour and settlement of the foundation. The observations and numerical results are discussed
and an explanation is presented based on results of cyclic laboratory tests. 相似文献
16.
The Australian continent has an enigmatic present-day stress pattern with considerable regional variability in maximum horizontal stress (SHmax) orientations. Previous attempts to estimate the Australian SHmax orientation with geomechanical–numerical models indicate that plate boundary forces provide the major controls on the contemporary stress orientations. However, these models do not satisfactorily predict the observed stress orientation in major basins throughout eastern Australia, where the knowledge of the present-day crustal stresses is of vital importance for development and management of different types of geo-reservoirs. In addition, a new comprehensive stress-data compilation in Australia, which contains 2150 data records and is the key dataset for model calibration, provides motivation to construct a new geomechanical–numerical model for Australia. Herein, we present a 3D geomechanical–numerical model that predicts both the SHmax orientation and the relative stress magnitudes throughout the Australian continent. Our best-fit model, with mean absolute deviation of 15°, is in good agreement with observed SHmax orientations and the stress regime in most areas, and shows a much better fit in areas where the stress pattern was unable to be predicted by previous published attempts. Interestingly, the best-fit model requires a significant push from the western boundary of Australian continental model, which is possible supporting evidence for the east–west-oriented mantle drag postulated by state-of-the-art global convection models, or may be generated by the excess of gravitational potential energy from Tibetan Plateau, transferred through the Indo-Australian Plate. Hence, our modelling results provide a good first-order prediction of the stress field for areas where no stress information is currently available and can be used to derive initial and boundary conditions for local and reservoir-scale 3D geomechanical models across Australia. 相似文献
17.
The development of a predictive model of behaviour of porous media during injection of miscible grout, taking into account convection, dilution and filtration of grout solution with interstitial water, as well as consolidation aspects, is presented. Model assumptions are reviewed and discussed first. During the establishment of the model, we insist on surface terms and their physical relevance in expressing adsorption effects. Constitutive laws such as Fick's law for diffusive mass transport, hydrodynamic dispersion tensor dealing with miscibility, are modified by taking into account filtration effects. A new surface term appears in mass balance equations as a consequence of filtration. According to the filtration laws used, an initial filtration rate is estimated on the basis of a one‐dimensional experimental campaign. The field equations are discretized by using Galerkin finite element and θ‐scheme standard method. For transport equation, Streamline Upwind Petrov Galerkin method is employed to prevent numerical oscillations. Lastly, confrontation of numerical results with laboratory experiments constitutes a first step to validate the model on a realistic basis. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
18.
This paper analyzes the emergence of channeling and preferential flow in heterogeneous porous media. Connectivity is studied
through the statistical characterization of the length L of connected, high velocity patterns in both two-dimensional and three-dimensional media. A simple, physically based, fully
analytic expression for the probability of L has been derived. It is found that the length L of connected, high velocity channels is flow-related and can be much larger than the conductivity integral scale I. Heterogeneity has a considerable impact on emergence of channeling patterns; connectivity is considerably enhanced in three-dimensional
structures as compared to two-dimensional ones. The strong dependence on space dimensionality is a warning against the use
of two-dimensional numerical models for assessing connectivity and preferential flow in heterogeneous media. The probability
p(L) is employed in order to determine the early arrivals of the breakthrough curve at a given control plane; the simple model
can be used for a preliminary assessment of preferential flow. Comparison with numerical simulations confirms that the main
connectivity features were adequately captured by the model. 相似文献
19.
The mathematical structure and numerical analysis of classical small deformation elasto–plasticity is generally well established. However, development of large deformation elastic–plastic numerical formulation for dilatant, pressure sensitive material models is still a research area. In this paper we present development of the finite element formulation and implementation for large deformation, elastic–plastic analysis of geomaterials. Our developments are based on the multiplicative decomposition of the deformation gradient into elastic and plastic parts. A consistent linearization of the right deformation tensor together with the Newton method at the constitutive and global levels leads toward an efficient and robust numerical algorithm. The presented numerical formulation is capable of accurately modelling dilatant, pressure sensitive isotropic and anisotropic geomaterials subjected to large deformations. In particular, the formulation is capable of simulating the behaviour of geomaterials in which eigentriads of stress and strain do not coincide during the loading process. The algorithm is tested in conjunction with the novel hyperelasto–plastic model termed the B material model, which is a single surface (single yield surface, affine single ultimate surface and affine single potential surface) model for dilatant, pressure sensitive, hardening and softening geomaterials. It is specifically developed to model large deformation hyperelasto–plastic problems in geomechanics. We present an application of this formulation to numerical analysis of low confinement tests on cohesionless granular soil specimens recently performed in a SPACEHAB module aboard the Space Shuttle during the STS‐89 mission. We compare numerical modelling with test results and show the significance of added confinement by the thin hyperelastic latex membrane undergoing large stretching. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
20.
An analytical model for vapor‐phase volatile organic compound diffusion through landfill composite covers 下载免费PDF全文
下载免费PDF全文 Haijian Xie Huaxiang Yan Hywel R. Thomas Shijin Feng Qihua Ran Peixiong Chen 《国际地质力学数值与分析法杂志》2016,40(13):1827-1843
One‐dimensional mathematical models for vapor‐phase volatile organic compound (VOC) diffusion through composite cover barriers are presented. An analytical solution to the model was obtained by the method of separation of variables. The results obtained by the proposed solution agree well with those obtained by a numerical analysis. Based on the proposed analytical model, the VOC breakthrough curves of five different composite covers are compared. The effects of degree of saturation of geosynthetic clay liner (GCL) or compacted clay liner (CCL) on VOC migration in the composite covers are then presented. Results show that the composite cover barriers provide much better diffusion barriers for VOC than the single CCL. The top surface steady‐state flux for a composite barrier, consisting of a 1.5 mm geomembrane (GM) and a 20 cm CCL, can be 8.3 times lower than that for a 30 cm CCL. The surface steady‐state flux for the case with (1.5 mm GM + 6 mm GCL) was found to be 2.3 times lower than that for the case with (1.5 mm GM + 20 cm CCL). The degree of saturation Sr of the CCL has a great influence on VOC migration in composite covers when Sr is larger than 0.5. The steady‐state flux at the surface of GM for the case with Sr = 0.7 can be 1.8 times lower than that for the case with Sr = 0.2. The proposed analytical model is relatively simple and can be used for verification of complicated numerical models, analysis of experimental data and performance assessment of composite cover barriers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献