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Investigation of failure analysis of clay reinforced with sand encapsulated
Enquête sur l'analyse des défaillances d'argile renforcé avec du sable enrobe
Tabarsa A.R.
Faculty of Engineering, Golestan University, Gorgan, IRAN
Hajiesmaeilian S.
Islamic Azad University, Science and Research, IRAN.
ABSTRACT: The paper includes discussions on the theory studies and numerical analysis as to stabilityof slopes reinforced with
geotextile encapsulated with lenses of sand. In this study, given the laboratory research conducted on clay reinforced with geotextile
encapsulated with lenses of sand, which showed in the high confining stresses due to the suitable interaction of clay and sand particles
with geotextile, significant improvement is obtained in shear strength. Considering these results, based on the stability importance of
slopesin the engineering projects and optimization, and increasing slopes stability, this technique is used as a reinforcement method in
the clay slopes using various methods of reinforcement and the effect of various conditions such as the number of layers of
reinforcement, confining pressures has been considered .In the study the numerical finite difference using software FLAC 2D has
been applied. The results showed that the slopes with higher height the Sandwich technique to typical reinforcement with geotextile
increases factor of stability safety under different studied scenarios because of improvement of intermediate behavior weakness by
thin sand layers and the amount of factor of stability safety has been also enhanced, increasing the number of reinforcement layers.
RÉSUMÉ : Le document comprend des discussions sur les études théoriques et l'analyse numérique que les pentes stabilityof
renforcés par des géotextiles encapsulés avec des lentilles de sable. Dans cette étude, compte tenu de la recherche en laboratoire
menées sur de l'argile renforcée avec géotextile encapsulés avec des lentilles de sable, qui a montré dans les fortes contraintes de
confinement en raison de l'interaction appropriée d'argile et de sable avec géotextile, une amélioration significative est obtenue dans la
résistance au cisaillement. Compte tenu de ces résultats, basés sur l'importance de la stabilité des slopesin les projets d'ingénierie et
d'optimisation, et d'augmenter la stabilité des pentes, cette technique est utilisée comme une méthode de renfort dans les pentes
argileuses en utilisant diverses méthodes de renforcement et de l'effet de diverses conditions telles que le nombre de couches de
renfort, des pressions de confinement a été pris en compte. Dans l'étude de la différence finie numérique à l'aide du logiciel FLAC 2D
a été appliqué. Les résultats ont montré que les pentes à plus forte hauteur de la Technique du sandwich à renfort typique avec un
facteur de sécurité augmente géotextile stabilité sous différents scénarios étudiés en raison de l'amélioration de la faiblesse
comportement intermédiaire par des couches de sable fin et la quantité de facteur de sécurité de stabilité a été améliorée également,
l'augmentation du nombre de couches de consolidation.
KEYWORDS: sandwich technique, reinforced soil, factor of safety, stability
1 INTRODUCTION
In non-reinforced backfills are constructed using natural
materials the constraints from poor materials used, methods and
non-favorable environmental andgeotechnical conditions on the
project site created failures or adverse conditions in the backfill.
Intensity and scope of the failures may be increased to some
extent that to impact the general and stability and complete
servicing the intended project. In addition in some exceptional
cases the project needs stimulate the engineers to consider
construction of backfills with special dimensions inslope or
height and stability against particularloadings such as
earthquake. For example construction of road or rail backfills
with more height or backfills with steep (in places due to
limited land, the possibility of Transverse extension of backfill
base missing) can be considered as specific items.Ineach of the
above mentioned cases the Constructionof reinforcedbackfills
with particular materials is felt,to be able to bear external
factors effects as well as to have suitablestability in
environmental and geotechnical conditions.
In the last three decades, Geosynthetics is widely used with
high tension resistance to the soil reinforcement in geotechnical
engineering. Makes using thereinforcesprovidesoil tension
resistance in the soil and thus reduce lateral deformation of soil
and increase overall stability of reinforced soil structures
(Abiera,H.O.1991).
In past decades, mostly the reinforced soil technique has
been applied using coarse materials as backfill (Backfill
materials). Recently, due to economic considerations, the
backfill material with low qualityand localaccess has been used
successfully (Bergado et al. 2008). Although you need to
determine the geotechnical properties for reinforcement
elements and backfill materials to design reinforced soil system,
but the mechanism of interaction of soil - reinforcementelement,
plays an important role.
To consider soil interaction mechanisms – reinforcement
element, studies have been done using direct shear and tension
tests by various researchers (Zhenggui Wang and Werner
Richwien 2002).
In the reinforced clay Soil, the contact resistance is low and
consequently, failure in interfaceoccur prior to the
reinforcertension strength to the final extent. Thus, a large
percentage of the tension strength of reinforcernot mobilized at
failure and cannot be used (Jewell.R.A and Wroth,C.P .1987).
Experimental results show that the shear stress around
reinforcementis high and decreases rapidly with distance from
its surface. Thus in the reinforced soil structures with low
quality backfill material it is possible that a thin layer with
granular material containing high resistance around the
reinforcement will be used to control high shear stresses near
the reinforce and in the interface (Ghiassian and Jahannia 2004).
This method improves the stress transfer mechanism due to a
