Plaxis bv

Delft, Netherlands

Plaxis bv

Delft, Netherlands
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Grant
Agency: European Commission | Branch: FP7 | Program: MC-IAPP | Phase: FP7-PEOPLE-IAPP-2008 | Award Amount: 1.28M | Year: 2009

The aim of the proposed Marie Curie IAPP project is to develop, validate and demonstrate new robust numerical tools for modelling large deformation problems in geotechnics, considering both quasi-static and dynamic applications. Examples of such applications are the interaction between soil and foundations during installation, service and failure, a well as prediction of slope stability (mass gravity flow problems). The main focus will be in modelling installation effects in geotechnics. From the scientific point of view, the project involves major development and extension of the Material Point Method (MPM), and enhancement and further development of material models for describing the complex rate-dependent stress-strain-strength behaviour of natural geomaterials. In parallel, it also involves further development of various extended finite element methods to account for installation effects, which have the potential to become routine design tools in the future. The core of the proposed project is to validate and demonstrate the new methods and tools for modelling installation effects in geotechnics, which involved real field applications, through intense collaboration between industry and academia. In parallel, the project aims to strengthen and expand the collaborative links between the partners and to increase the R&D input and innovation in the geotechnical field. The philosophy/approach is problem driven, e.g. the numerical tools are developed to solve challenging problems of practical importance.


Haxaire,Plaxis Bv | Aukenthaler M.,Plaxis Bv | Brinkgreve R.B.J.,Technical University of Delft
Procedia Engineering | Year: 2017

Recently, a constitutive model has been developed to describe the mechanical behaviour of frozen soil as a function of temperature, all the way to the unfrozen state, and vice versa [1]. The model has been implemented as a user-defined soil model (UDSM) in the geotechnical finite element code PLAXIS 2D and applied in practical thermo-hydro-mechanical boundary value problems. One of the problems with the use of a model for frozen / unfrozen soil is that it involves several parameters of which quite a few are not very common to geotechnical engineers. Hence, one of the goals of this study is to provide more information on the meaning and the determination of the model parameters. As an example of the use of the constitutive model and its implementation, one application is presented: it is a chilled pipeline causing a drop in the ground temperature leading to frost heave. Its results show that the model can simulate frost heave in a qualitative manner, and that the robustness of the numerical implementation is still sensitive to the choice of boundary conditions, temperature gradients, and time. © 2017 The Authors.


Coombs W.M.,Durham University | Crouch R.S.,City University London | Heaney C.E.,Plaxis BV
Journal of Engineering Mechanics | Year: 2013

Linear elastic-perfect plasticity using the Mohr-Coulomb yield surface is one of the most widely used pressure-sensitive constitutive models in engineering practice. In the area of geotechnical engineering, a number of problems, such as cavity expansion, embankment stability, and footing bearing capacity, can be examined using this model together with the simplifying assumption of plane strain. This paper clarifies the situation regarding the direction of the intermediate principal stress in such an analysis and reveals a unique relationship between hydrostatic pressure and the principal stress ratio for Mohr-Coulomb and Tresca perfect plasticity under those plane-strain conditions. The rational relationship and direction of the intermediate principal stress are illustrated through both material-point and finite-element simulations. The latter involves the analysis of a rigid strip footing bearing onto a weightless soil and the finite-deformation expansion of a cylindrical cavity. © 2013 American Society of Civil Engineers.


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.


Lee S.W.,Geotechnical Consulting Group Asia Ltd | Cheang W.W.L.,Plaxis Asia | Swolfs W.M.,Plaxis BV | Brinkgreve R.B.J.,Technical University of Delft
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010

There has been an increasing use of three-dimensional finite element analyses to analyse the behaviour of piled raft foundations. The raft-piles-soil interaction can be fully modelled for complex ground conditions and pile arrangements. This paper uses the Plaxis3DFoundation programme to model the performance of two well-documented piled raft foundations in the Frankfurt clay, Germany. The piles are modelled by solid elements with/without interface elements and embedded piles. The embedded pile approach predicts the raft settlements and the load sharing between the raft and the piles in good agreement with the interfaced solid pile approach. The predictions made by the two approaches fall within +/-10% of the measurements. © 2010 Taylor & Francis Group, London.


Galavi V.,Plaxis B.V. | Brinkgreve R.B.J.,Technical University of Delft
Numerical Methods in Geotechnical Engineering - Proceedings of the 8th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2014 | Year: 2014

This paper investigates finite element modelling of moving loads on geotechnical structures. Moving loads can be modelled in different ways such as equivalent nodal forces, time step adjustment, mesh refinement, convective coordinates, boundary element method and coupled boundary element method and finite element method. After summarising possibilities and limitation of each method, the equivalent nodal forces method will be discussed in more detail. In this approach, the nodal forces are calculated in every time step according to the load's position and element shape function. Numerical issues, which need to be considered in order to achieve accurate results, are discussed. Finally, a moving point load on an elastic domain is numerically simulated and the results are compared with an analytical solution. © 2014 Taylor & Francis Group.


Sivasithamparam N.,University of Strathclyde | Sivasithamparam N.,Plaxis B.V | 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.


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.


Grant
Agency: European Commission | Branch: FP7 | Program: MC-IAPP | Phase: FP7-PEOPLE-IAPP-2008 | Award Amount: 403.23K | Year: 2009

Failures of long span highway structures in Northridge earthquake (1994) and spatially extended transmission towers systems in Kobe earthquakes (1995) have clearly shown the significance of non-stationary effects of ground motions and its importance in earthquake geotechnical engineering. Similar detrimental vibration effects have been witnessed in vehicle induced ground transmission of vibrations from high speed railway tracks, both underground and at surface. There has been a rapid growth of infrastructure and transportation systems (like tunnels, pipelines etc.) in Europe over the last few decades, which are spatially extended structures. The non-stationary effects of vibrations are threatening to the safety of these systems making them vulnerable to vibrations transmitted through soil medium. The recent European design codes require these systems to be analysed for safety against spatially varying vibration effects, which will be mandatory in near future. The Structural Dynamics & Vibrations Group (SDVG) in Trinity College Dublin, Ireland has excellent research background on non-stationary vibration analysis with international reputation, and PLAXIS BV an SME in The Netherlands is a world leader in the field of finite element modelling in geotechnical engineering with emphasis on soil-structure interaction. The PLAXIS BV is a European technical IT company which has a range of user friendly technical software products for the infrastructure industry worldwide. This project provides a framework to bring the two partners (from academia and industry) together with complementary expertise, to transfer the knowledge for mutual benefit and development. It will contribute to the knowledge base development of a European SME with global market, innovating new products. It will also foster the FP7 targets of Sustainable Transport with safety and security under to man-made and naturally induced vibrations; applying the tools developed using Information Science & Technology.


Brinkgreve R.B.J.,Technical University of Delft | Brinkgreve R.B.J.,Plaxis B.V. | Engin E.,Plaxis B.V. | Engin H.K.,Technical University of Delft
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010

The right selection of soil model parameters is essential to make good predictions in geo-engineering projects where the Finite Element Method (FEM) is used. In order to support geotechnical engineers with soil model parameter selection, empirical formulas have been developed to derive the model parameters of the Plaxis Hardening Soil model with small-strain stiffness (HSsmall), on the basis of a characteristic property (relative density for sands and plasticity index for clays). This paper shows a validation of formulas for sands which have been derived from published soil testing data. The main goal of the empirical formulas is to give a reasonable first order approximation of soil behaviour in FEM calculations, covering a wide range of sands. In a case study it is demonstrated that the empirical formulas work reasonably well to get a first estimate of deformations and stress developments for a real project. © 2010 Taylor & Francis Group, London.

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