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1
Content available Size Effects in Problems of Footings on Sand within Micro-Polar Hypoplasticity
Tejchman J., Górski J.
Archives of Hydro-Engineering and Environmental Mechanics
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2008
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Vol. 55, nr 3-4
95-124
EN
Numerical FE investigations of size effects in problems of footings on sand were performed. Micro-polar hypoplastic constitutive model was used to describe a mechanical behaviour of a cohesionless granular material during a monotonic deformation path. The FE analyses were carried out with three different footing widths. In deterministic calculations, a uniform distribution of initial void ratio was used. In statistical calculations, initial void ratios took the form of random spatial fields described by a truncated Gaussian random distribution. In order to reduce the number of stochastic realizations without sacrificing the accuracy of the calculations, a stratified sampling method was applied. The numerical results were compared with corresponding laboratory tests by Tatsuoka et al (1997). The numerical results show that the bearing capacity of footings decreases with increasing specimen size. If the initial void ratio is stochastically distributed, the mean bearing capacity of footings may be larger than the deterministic value. The statistical size effect is smaller than the deterministic one.
2
Content available Stochastic FE-analysis of shear localization in 2D granular material within a micro-polar hypoplasticity
Tejchman J., Górski J.
Archives of Hydro-Engineering and Environmental Mechanics
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2006
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Vol. 53, nr 4
353-379
EN
The paper deals with investigations of the effect of the stochastic distribution of the initial void ratio in granular bodies on shear localization during shearing of an infinite granular layer 500 mm high with free dilatancy under plane strain conditions. The initial void ratio was assumed to be stochastic with a correlated random field generated by a conditional rejection method by Walukiewicz et al (1997). To simulate mechanical behaviour of a cohesionless granular material during a monotonous deformation path, a micro-polar hypoplastic constitutive law was used, which takes into account particle rotations, curvatures, non-symmetric stresses, couple stresses and the mean grain diameter as a characteristic length. The proposed model captures the salient mechanical features of granular bodies in a wide range of densities and pressures with a single set of constants. In addition, the comparative FE-analyses were carried out with a uniform and spatially non-correlated random fields of the initial void ratio.
3
Content available Simulation of shear localization in granular bodies within gradient-enhanced hypoplasticity
Tejchman J.
Archives of Hydro-Engineering and Environmental Mechanics
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2004
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Vol. 51, nr 3
243-265
EN
The paper presents a FE-analysis of a spontaneous shear localization inside non-cohesive sand during plane strain compression. The calculations were carried out with a gradient-enhanced hypoplastic constitutive law. The hypoplastic law can reproduce essential features of granular bodies depending on the void ratio, pressure level and deformation direction. To model the thickness of shear zones, a characteristic length of the microstructure was incorporated via the second gradient of the modulus of the deformation rate. To determine the effect of micro-structure, the analysis was performed with different characteristic lengths for the same specimen size.
4
Content available Fe-analysis of patterning of shear zones in granular bodies for earth pressure problems of a retaining wall
Tejchman J.
Archives of Hydro-Engineering and Environmental Mechanics
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2004
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Vol. 51, nr 4
317-348
EN
The evolution of shear zones in granular bodies for earth pressure problems of a retaining wall in conditions of plane strain was analyzed. The passive and active failure of a retaining wall was discussed. The calculations were carried out with a rigid and very rough retaining wall undergoing horizontal translation, rotation around the top and rotation around the bottom. The behaviour of dry sand was numerically modelled with a finite element method using a hypoplastic constitutive relation with polar extensions. Attention was paid to the influence of different wall movements on shear localization. The initial void ratio was assumed to be non-uniformly distributed. The geometry of calculated shear zones was compared with corresponding experimental results of laboratory model tests.
5
Content available A Non-local hypoplastic constitutive law to describe shear localisation in granular bodies
Tejchman J.
Archives of Hydro-Engineering and Environmental Mechanics
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2003
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Vol. 50, nr 4
359-379
EN
The paper presents a FE-analysis of shear localisation in granular bodies by a finite element method based on a hypoplastic constitutive law. The law can reproduce essential features of granular bodies depending on the void ratio, pressure level and deformation direction. To realistically simulate the formation of a spontaneous shear zone inside cohesionless sand during plane strain compression, a hypoplastic constitutive law was extended by non-local terms. The effects of initial void ratio, pressure level and a characteristic length on the thickness of an interior shear zone were shown. The numerical results were compared with corresponding laboratory tests.
6
Content available remote Evolution of shear localisation in earth pressure problems of a retaining wall
Tejchman J.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2002
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Vol. 6, No 3
387-410
EN
The paper deals with numerical investigations of the evolution of shear localisation in granular bodies for earth pressure problems of a retaining wall in conditions of plane strain. The passive and active failure of a retaining wall in sand is discussed. The calculations are carried out with a rigid and very rough retaining wall undergoing horizontal translation, rotation around the top and rotation around the bottom. The behaviour of dry sand is numerically modelled with a finite element method using a hypoplastic constitutive relation within a polar (Cosserat) continuum. The constitutive relation is obtained through extension by polar quantities, viz. rotations, curvatures and couple stresses, using the mean grain diameter as a characteristic length. During FE-calculations, the attention is laid on the influence of different wall movements on shear localisation. In addition, the effects of the initial void ratio, distribution of the initial void ratio and mean grain diameter, pressure level and size of the sand body and retaining wall is investigated in the case of a passive wall translation. The FE-results are compared with corresponding experimental results of laboratory model tests.
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