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Delft, Netherlands

Razouki S.S.,Ruhr University Bochum | Bonnier P.,Plaxis bv | Datcheva M.,Bulgarian Academy of Science | Schanz T.,Ruhr University Bochum
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2013

Presented and discussed in this paper is an exact analytical solution of the nonhomogeneous partial differential equation governing the conventional one-dimensional consolidation under haversine repeated loading. The derived analytical solution to the 1D consolidation equation is compared with the numerical solution of the same consolidation problem via FEM. The series solution takes into account the frequency of repeated loading through a dimensionless time factor T0. The paper reveals that an increase in the frequency of imposed repeated haversine loading (a decrease in period of repeated loading) causes an increase in the number of cycles required to achieve the steady state, whereas the effect of frequency on the maximum excess pore water pressure at the bottom of a clay layer with permeable top and impermeable bottom for the range of frequencies studied is generally insignificant. The effective stress at the bottom of the clay deposit with permeable top and impermeable bottom increases with time but with some fluctuations without changing the sign. These fluctuations become more pronounced for increasing values of T0. An increase in T0 also causes an increase in maximum effective stress. © 2013 John Wiley & Sons, Ltd.

Engin H.K.,Technical University of Delft | Engin H.K.,Norwegian Geotechnical Institute | Brinkgreve R.B.J.,Technical University of Delft | Brinkgreve R.B.J.,Plaxis bv | And 2 more authors.
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2015

This paper presents a simplified finite element analysis technique, the 'Press-Replace' technique, to model pile penetration problems in geotechnical engineering, particularly, pile jacking. The method is employed in standard finite element analysis software. The method involves a straining and a consequent geometry update phase. First, a cone penetration test in (undrained) clay is modelled and compared with the results of analytical, semi-analytical and more advanced finite element techniques. The model sensitivity for the step size and mesh is investigated using a hypoplastic constitutive model. An optimum way of modelling based on the numerical performance is shown. © 2015 John Wiley & Sons, Ltd.

Galavi V.,Plaxis bv
Computational Geomechanics, COMGEO II - Proceedings of the 2nd International Symposium on Computational Geomechanics | Year: 2011

Finite element formulation of thermo-hydro-mechanical analysis is presented in this study. The governing equations are derived for saturated and partially saturated soils. Flow of water in both liquid and gas phase as well as heat flow are considered. The study is based on the assumption that the air pressure is constant and therefore air flow is ignored. A fully implicit scheme is used to solve the problem. Finally, an example is presented to show the capability of the formulation to simulate non-isothermal consolidation.

Sivasithamparam N.,University of Strathclyde | Sivasithamparam N.,Plaxis bv | Kamrat-Pietraszewska D.,University of Strathclyde | Karstunen M.,University of Strathclyde
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010

This paper describes the principles behind a new anisotropic bubble model for natural soils. The model is a hierarchical extension of the anisotropic S-CLAY1 model. The kinematic yield surface of S-CLAY1 model is treated as a bounding surface and a bubble surface is introduced within the bounding surface. The bubble surface is similar in shape to the S-CLAY1 yield surface, and assumes an isotropic elastic behaviour and an associated flow rule. A translation rule of the bubble is used to control the movement of the bubble. The implementation of the model is first verified by simulating slow cyclic loading with constant deviator stress on Kaolin clay, and secondly, simulations of undrained triaxial shear tests (in compression and extension) are made to highlight the effect of evolution of anisotropy, and finally, simulations of high number of loading cycles performed to examine ratcheting feature of the model. © 2010 Taylor & Francis Group, London.

Sivasithamparam N.,Norwegian Geotechnical Institute | Karstunen M.,Chalmers University of Technology | Karstunen M.,University of Strathclyde | Bonnier P.,Plaxis bv
Computers and Geotechnics | Year: 2015

This paper presents a three dimensional constitutive model that describes the creep behaviour of natural clays with anisotropic stress-strain response, focussing on robust model implementation. Creep is formulated using the concept of a constant rate of visco-plastic multiplier, resulting in a formulation with easily determined creep parameters. A key assumption in the model formulation is that there is no purely elastic domain. Of the 10 input parameters that can be defined based on standard laboratory testing, five are similar to those used in the Modified Cam-Clay model. The performance of the model at element level and boundary value level is demonstrated, for the latter by comparing the simulations with the measured response of Murro test embankment in Finland. For comparison, the simulations are also done using the previously published anisotropic creep model and an equivalent rate-independent model. This enables studying the role of evolution anisotropy and creep at boundary value level by systematic comparisons. © 2015 The Authors.

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