| 1. |
- Larsson, Ragnar, et al.
(författare)
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Localization properties of a frictional material model based on regularized strong discontinuity
- 1996
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - 0363-9061 .- 1096-9853. ; 20:11, s. 771-783
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Tidskriftsartikel (refereegranskat)abstract
- A frictional material model is investigated with respect to the existence and development of a regularized strong discontinuity within the constitutive framework of plasticity theory. It appears that the condition for the existence of such a discontinuity is identical to the classical bifurcation criterion for band shaped bifurcation in the rate of deformation field. The model behaviour is also discussed beyond onset of localization, for a band with fixed orientation, where the state variables are allowed to change.
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| 2. |
- Mattsson, Hans, et al.
(författare)
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Method to correct yield surface drift in soil plasticity under mixed control and explicit integration
- 1997
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - 0363-9061 .- 1096-9853. ; 21:3, s. 175-197
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Tidskriftsartikel (refereegranskat)abstract
- When applying an explicit integration algorithm in e.g. soil plasticity, the predicted stress point at the end of an elastoplastic increment of loading might not be situated on the updated current yield surface. This so-called yield surface drift could generally be held under control by using small integration steps. Another possibility, when circumstances might demand larger steps, is to adopt a drift correction method. In this paper, a drift correction method for mixed control in soil plasticity, under drained as well as undrained conditions, is proposed. By simulating triaxial tests in a Constitutive Driver, the capability and efficiency of this correction method, under different choices of implementation, have been analysed. It was concluded that the proposed drift correction method, for quite marginal additional computational cost, was able to correct successfully for yield surface drift giving results in close agreement to those obtained with a very large number of integration steps.
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| 3. |
- Tan, Xiang Chun, et al.
(författare)
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Application of a splitting fracture model to the simulation of rock indentation subsurface fractures
- 1997
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - 0363-9061 .- 1096-9853. ; 21:1, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional fracture model based on micro-fracture mechanics is applied to the Hertzian indentation stress field to simulate subsurface fractures in an axi-symmetrical plane. The simulation of fracture development reveals quantitatively the effects of loading force, mechanical properties of the rocks, and original micro cracks on the formation of subsurface fractures. The distribution patterns of the subsurface fractures are determined by the magnitudes and trajectories of the indentation stresses. Lateral confinement prohibits the fracture development. Simulations of the subsurface fractures in granite and marble are in good agreement with the indentation experiments.
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| 4. |
- Alawaji, H., et al.
(författare)
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Implicit integration in soil plasticity under mixed control for drained and undrained response
- 1992
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 16:10, s. 737-756
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Tidskriftsartikel (refereegranskat)abstract
- An algorithm is outlined for the implicit integration of isotropic plasticity models for an arbitrary choice of mixed stress and strain control variables. Drained as well as undrained behaviour is considered. The closest-point-projection method in conjunction with a completely strain-driven format is used in a core algorithm. In the drained case strain response variables are determined via iterations to satisfy equilibrium of prescribed and calculated stresses that correspond to the strain response variables. In the undrained case, on the other hand, strains and pore pressure are determined via simultaneous iterations to satisfy equilibrium and the incompressibility condition. The algorithm is applied to a new generalized cam-clay model, and various iteration techniques are assessed. In particular, Newton iterations which employ the matrix of algorithmic tangent stiffness moduli are shown to compete favourably with more conventional methods.
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| 5. |
- Bagheri, Mehdi, et al.
(författare)
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Investigation of model uncertainty for block stability analysis
- 2011
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 35:7, s. 824-836
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Tidskriftsartikel (refereegranskat)abstract
- The application of probabilistic design, such as FORM, is expanding rapidly in the design of geotechnical structures. The analytical solution proposed by Crawford and Bray for analyzing block stability can be used as a performance function to carry out probabilistic design. The solution benefits from considering both clamping forces and joint stiffness. However, imperfect assumptions and simplifications in the solution generate model uncertainties. The amount of model uncertainty must be considered in order to assess a reliable design. The purpose of this paper is to identify when the analytical solution is applicable and quantify the model uncertainty of the solution. The amount of model uncertainty for the analytical solution has been assessed for different conditions. The results show that at a shallow depth with a low value of in situ stress ratio (horizontal stress/vertical stress), the analytical solution predicts that the block is stable whereas DEM shows that the block is unstable. The results of the analyses indicate that in cases with low stress ratio, cases with high anisotropy of joint stiffness or the case of a semiapical angle close to the friction angle, the accuracy of the analytical solution is low. Neglecting key parameters, such as the absolute value of joint shear and normal stiffness, vertical in situ stress and its influence on joint relaxation generate model uncertainty in the analytical solution. The analyses show that by having more information about the key parameters, the model uncertainty factor could be identified more precisely.
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| 6. |
- Digby, Peter J., et al.
(författare)
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Finite element simulation of time dependent fracture and fragmentation processes in rock blasting
- 1985
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 9:4, s. 317-329
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Tidskriftsartikel (refereegranskat)abstract
- Two constitutive models for the simulation of fracture and fragmentation processes in rapidly loaded rocks are studied. The models were included in a wave propagation finite element code. The results obtained from the two models were compared by a study of the intensity and extent of fracturing obtained from two different configurations of explosive charge and reflecting surfaces in a plane strain problem. The evolution of the time dependent fracture pattern and fragmentation process is also presented.
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| 7. |
- Grassl, Peter, 1974, et al.
(författare)
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Plastic model with non-local damage applied to concrete
- 2005
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 30:1, s. 79-90
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Tidskriftsartikel (refereegranskat)abstract
- The present paper deals with a certain class of regularized models for concrete failure, combining plasticity with non-local damage. The plastic part is local and uses a yield condition formulated in the effective stress space. Softening is incorporated through the damage part of the model. Damage is considered as isotropic and linked to the evolution of plastic strain. The regularized version of the model is based on weighted spatial averaging of the damage-driving variable. Conditions for a mesh-independent description of the localized zone of inelastic strains are studied using one- and two-dimensional examples solved by simple non-local damage-plasticity models, in two dimensions with non-associated flow. Then, the framework is applied to an advanced model for concrete. Structural examples with tensile and compressive failure are presented. Copyright © 2005 John Wiley & Sons, Ltd.
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| 8. |
- Jafarzadeh, Ata, 1992, et al.
(författare)
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Surface load dynamic solution of saturated transversely isotropic multilayer half-space
- 2019
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - : Wiley. - 0363-9061 .- 1096-9853. ; 43:9, s. 1655-1685
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Tidskriftsartikel (refereegranskat)abstract
- This paper treats the dynamic response of a multilayered transversely isotropic fluid saturated poroelastic half-space under surface time-harmonic traction. The governing system of partial differential equations is uncoupled with the use of a set of physically meaningful and complete potential functions that decompose different body waves in a saturated poroelastic transversely isotropic medium. After expressing the equations in the Hankel-Fourier domain, a proper algebraic factorization is applied to generate reflection and transmission matrices for decomposed waves. All responses including displacements, stresses, and pore fluid pressure for both general patch load and point load are presented in the form of semi-infinite line integrals. The verification of the method is confirmed with the degeneration of the solutions presented here to the existing solutions for dried both homogeneous and multilayered elastic half-spaces as well as poroelastic half-space. Selected numerical results are depicted to investigate the effects of layering and pore pressure on responses of a transversely isotropic poroelastic medium. The load distribution effects are studied by comparison of the patch and point load responses. Also, resonance notion and effective parameters on this phenomenon such as layering system and anisotropy contrast are discussed. Significant influence of materials and layering configuration on number and amplitude of resonances depicted through the numerical evaluation.
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| 9. |
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| 10. |
- Kettil, Per, 1972, et al.
(författare)
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Coupled simulation of wave propagation and water flow in soil induced by high-speed trains
- 2008
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Ingår i: International Journal for Numerical and Analytical Methods in Geomechanics. - 0363-9061 .- 1096-9853. ; 32:11, s. 1311-1319
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this paper is to simulate the coupled dynamic deformation and water flow that occur in saturated soils when subjected to traffic loads, which is a problem with several practical applications. The wave propagation causes vibrations leading to discomfort for passengers and people in the surroundings and increase wear on both the vehicle and road structure. The water flow may cause internal erosion and material transport in the soil. Further, the increased pore water pressure could reduce the bearing capacity of embankments. The saturated soil is modelled as a water-saturated porous medium. The traffic is modelled as a number of moving wheel contact loads. Dynamic effects are accounted for, which lead to a coupled problem with solid displacements, water velocity and pressure as primary unknowns. A finite element program has been developed to perform simulations. The simulations clearly demonstrate the induced wave propagation and water flow in the soil. The simulation technique is applicable to railway as well as road traffic.
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