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Large deformation and post-failure simulations of segmental retaining walls using
mesh-free method (SPH)
Simulations de grandes déformations et post-rupture des murs de soutènement segmentaires
utilisant la méthode des mailles-libres (SPH)
Bui H.H., Kodikara J.A, Pathegama R., Bouazza A., Haque A.
Department of Civil Engineering, Monash University, Melbourne, Vic 3800, Australia.
ABSTRACT: Numerical methods are extremely useful in gaining insights into the behaviour of reinforced soil retaining walls.
However, traditional numerical approaches such as limit equilibrium or finite element methods are unable to simulate large
deformation and post-failure behaviour of soils and retaining wall blocks in the reinforced soil retaining walls system. To overcome
this limitation, a novel numerical approach is developed aiming to predict accurately the large deformation and post-failure behaviour
of soil and segmental wall blocks. Herein, soil is modelled using an elasto-plastic constitutive model, while segmental wall blocks are
assumed rigid with full degrees of freedom. A soft contact model is proposed to simulate the interaction between soil-block and
block-block. A two dimensional experiment of reinforced soil retaining walls collapse was conducted to verify the numerical results.
It is shown that the proposed method can simulate satisfactory post-failure behaviour of segmental wall blocks in reinforced soil
retaining wall systems. The comparison showed that the proposed method can provide satisfactory agreement with experiments.
RÉSUMÉ : Les méthodes numériques sont extrêmement utiles pour obtenir un aperçu du comportement des murs de soutènement en
sol renforcé. Cependant, les approches numériques traditionnelles tels que l'équilibre limite ou méthodes d'éléments finis sont
incapables de simuler les déformations importantes et le comportement post-rupture des sols et les blocs de béton des murs de
soutènement segmentaires. Pour contourner cette limitation, une nouvelle approche numérique est présentée dans cet article. Le sol
est modélisé à l'aide d'un modèle élasto-plastique, tandis que les blocs segmentaires muraux sont supposés être rigides avec une degré
de liberté total. Un modèle de contact souple a été développé pour modéliser l'interaction entre le sol-bloc et bloc-bloc. Un modèle
expérimentale en deux dimensions d’un effondrement d’un mur de soutènement renforcé a été réalisé pour vérifier les résultats
numériques. Il est montré que la méthode de simulation proposée permet de simuler le comportement post-rupture des blocs de mur
segmentaires des murs de soutènement renforcé. La comparaison a montré que la méthode proposée peut fournir un accord
satisfaisant avec les résultats expérimentaux.
KEYWORDS: retaining wall modelling, segmental walls, large deformation and failure, mesh-free, SPH.
1 INTRODUCTION
In recent years, segmental retaining walls (SRWs) have
received great attentions for their low material cost, short
construction period, ease of construction, and aesthetic
appearance. They have been used as an effective method to
stabilize cuts and fills adjacent to highways, and embankments,
amongst many other applications. Because of the flexible
structural materials used (no mortar, or concrete footing), SRWs
can tolerate minor ground movement and settlement without
causing damage or cracks. In addition, dry stacked SRW
construction allows free draining of water through the wall face,
thereby reducing hydrostatic pressure build-up behind the wall.
Thus far, several analytical and numerical approaches have
been developed to assist SWR design. Among these techniques,
the finite element method (FEM) has been frequently applied to
investigate stability and settlement of segmental retaining wall
systems. FEM has also been used to simulate seismic load-
induced large deformation of SRW systems. However, because
of the mesh-based nature, FEM suffers from mesh entangling
when dealing with large deformation problems, even when the
updated Lagrangian method is adopted. Re-meshing may help
to resolve this problem but the procedure is quite complicated.
It is also worth mentioning that the free rotation motion of
retaining wall blocks in SWR systems could not be modeled by
FEMs. As an alternative for such computational complications,
it is attractive to develop mesh-free methods. So far, the most
popular mesh-free method applied in geotechnical engineering
is the discrete element method (DEM) which tracks the motion
of a large number of particles, with inter-particle contacts
modelled by spring and dashpot systems (Cundall & Strack,
1979). The main advantages of this approach are that it can
handle large deformation and failure problems; and the concept
is relatively simple and easy to implement in a computer code.
Thus, DEM could be considered an ideal method to simulate the
full degrees-of-freedom motion of the retaining wall blocks in
SRW systems. However, to model soil behaviour, DEM suffers
from low accuracy because suitable parameters for the contact
model are difficult to determine. The discontinuous deformation
analysis (DDA) method proposed by Shi et al. (1998) has also
been applied to geotechnical applications, but is mainly used for
rock engineering, etc. Other continuum based mesh-free
methods such as the mesh-free Galerkin element method (EFG),
material point method (MPM), particle in cell method (PIC),
etc., could be also applied to simulate large deformation of soil.
However, these methods are quite time consuming and
complicated to implement into a computer code as they consist
of both interpolation points and the background mesh. On the
other hand, the smoothed particle hydrodynamics (SPH) method,
originally proposed by Gingold & Monaghan (1977), has been
recently developed for solving large deformation and post-
failure behaviour of geomaterials (Bui et al. 2007-2012; Pastor
et al. 2009, Blanc et al. 2012) and represents a powerful way to
understand and quantify the failure mechanisms of soil in such
challenging problems. In this paper, taking into consideration
this unique advantage, SPH is further extended to simulate large
deformation and post-failure of SRW systems.
