IRJET- Numerical Analysis of L-Shaped Retaining Wall with Compressible Expanded Polystrene Under Static and Dynamic Condition

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 08 | Aug 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 881
Numerical Analysis of L-shaped Retaining Wall with Compressible
Expanded Polystrene Under Static and Dynamic Condition
Mrs. Pooja Y E1, Dr.L.Govindaraju2, Miss. Poornima D3, Mrs. Yajnodbhavi H M4
1,3,4Assistant Professor, Department of civil Engineering, PESITM, Shivamogga, Karnataka, India
2Associate Professor, Department of civil Engineering, UVCE, Banglore, Karnataka, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - A numerical model of L-shaped retaining wall is
developed using the finite element Plaxis programme to study
the effect of Expanded Polystrene(EPS) on the displacementof
L-shaped retaining wall due to lateral earth pressure under
static and dynamic loading condition. From the analysis it is
observed that the greater lateral earth pressure can be
reduced when Retaining wall is provided with EPS.
Key Words: Numerical model, Plaxis program,Retaining
Wall, Expanded polystrene(EPS),LateralEarthPressure.
1. INTRODUCTION
Earth retaining structures constitute an important
component ofmany civil engineeringworks.Thesestructures
may be of a number of types (e.g. reinforced concrete
retaining walls-gravityor cantilevered, bridge abutments or
basement walls) and they are designed to safely resist the
lateral pressures exerted by earth masses.
In earthquake prone areas an earth retaining structure must
be designed to be able to withstand the seismic earth
pressures in addition to the static ones. The provisions of
current seismic codes for estimating the earth thrust due to
the design earthquake are based mainly on the Mononobe-
Okabe method and their use results in a significant increase
of earth pressures under strongearthquakemotions[4].Poor
design in such cases may lead into serious damage or even
collapse of the retaining structure, with catastrophic
consequences to important infrastructure works. On the
other hand, the appropriate design against the increased
lateral -static plus dynamic loading results in a significant
increase in the construction cost. Despite the fact that the
validity of current seismic code provisions and the
applicability of assumptions made by analytical solutions to
practical retaining walls has recently been questioned the
design and dimensioning of such walls is still, and probably
will continue to be for some time in the future, based on the
existing codes.
Furthermore, recent research results from large scale shake
table tests have shown that for high ground accelerations,
significant earth pressure thrusts are measured on the
retaining structures [5]. For these reasons, a method for the
seismic earth pressure reduction (or isolation) would be
particularlywelcome by the civil engineering professionand
construction industry for both new and existing structures.
1.1 L-shaped Retaining Wall
Fig -1: L-shaped Retaining Wall
L-shapedwallsare simple toconstruct and thusoftenusedas
earthretainment constructions.Sincetheusualapproachesof
the design for overall stability (e.g. bearing capacity, sliding)
are believedto be reliable and sufficientlyaccurate,questions
remain concerning the magnitude of the earth pressure
acting on the vertical stem of the wall.
For the overall stability design a substitute retaining wall is
usually considered. This consists of the wall itselfandthesoil
behind the stem and above the wall base. The wall cross
section resists against driving static and dynamic forces by
means of its own weight and of the weight of the soil resting
on the foundation slab. Standard self-supporting L shape
retaining wall provides a cost effective solution where no
footings or other supporting structure is required.
1.2 Expanded polystyrene (EPS)
Blockor planarrigidcellularfoamedpolymericmaterialused
in geotechnical engineering applications.
Fig -2: Expanded Polystyrene

Expanded polystyrene (EPS) geofoam has been used as a
geotechnical material since the 1960s. EPS geofoam is
approximately 1% the weight of soil and less than 10% the
weight of other lightweight fill alternatives. As a lightweight
fill, EPS geofoam reduces the loads imposed on adjacent and
underlying soils and structures. EPSgeofoamis not a general
soil fill replacement material but is intended to solve
engineering challenges. The use of EPS typically translates
into benefits to construction schedulesandlowerstheoverall
cost of construction because it is easy to handle during
construction, often without the need for special equipment,
and is unaffected by occurring weather conditions. In
addition, EPS geofoam can be easily cut and shaped on a
project site, which further reduces jobsite challenges. EPS
geofoam is available in numerous material types that can be
chosen by the designer for a specific application. Its service
life is comparable to other construction materials and it will
retainits physical propertiesunder engineeredconditionsof
use.
1.3 PLAXIS
Plaxis is a special purpose two-dimensional finite element
computerprogram usedtoperformdeformationandstability
analysis for various types of geotechnical applications. Real
situations may be modeled either by a plane strain or an
axisymmetric model.
“Plaxis version 8.2” is a finite element software program
developedin the Netherlandsfor two and three-dimensional
analysis of geo-structures and geotechnical engineering
problems. It includes from the most basic to the most
advanced constitutive modelsfor the simulationof thelinear
or non-linear, time-dependent and anisotropic behaviour of
soil and/orrock. Plaxisis also equipped with featuresto deal
with various aspectsof complex structuresandstudythesoil-
structure interaction effect. In addition to static loads, the
dynamic module of Plaxis also provides a powerful tool for
modeling the dynamic response of a soil structure during an
earthquake.
The objectives of proposed studies includes-
To evaluate Lateral earth pressure on L-shaped Retaining
wall with EPS under static and dynamic case using Plaxis
program.
To evaluate Displacement of L-shaped Retaining wall with
EPS both in horizontal and vertical directions under static
and dynamic case using Plaxis program.
2. NUMERICAL ANALYSIS
Numerical analysis is carriedforL-shapedretainingwallwith
and without EPS
2.1 Model 1: Analysis of Rigid L-Shaped Retaining Wall
Fig -3: Geometry and Boundary condition.
Height of Retaining of wall(H) = 9m
Width of slab(B) = 5.4m
The geometry of the finite element model was constructed
using the graphical procedure of the Plaxis program. At this
stage, the geometry of the numerical model, the material
properties and the boundary conditions were specified.
The numerical analysis was carried out in plane strain, as
presented in Figure 3, the layout of the numerical model
extends 28m horizontally and 14m vertically to model the
prototype scale of the centrifuge container[1], these
boundary limits were assumed to be sufficient to avoid
borderdisturbances. Conditionsofplainstrainwereassumed
throughout; the verticalboundariesofthemodelwerepinned
in the horizontal direction but free to move vertically, and
the horizontal boundary at the base of the model was
assumed to be pinned in both vertical and the horizontal
directions. Additionally earthquake loads were taken for
dynamic analysis.
Fig -4: Deformed mesh
Plaxis input programme is used for the generation of the
model’s finite element mesh. A typical mesh generated is
shown in figure 4, the soil model was run with a finite mesh

2.1.1 Wall Modeling
The Retaining wall structure was simulated with one
dimensional linear beam element that can resist axial load
and bending moments. The stiffness for the wall element is
represented by means of the flexural rigidity EI and normal
stiffness EA, where A and E are the cross section area and
Young’s modulus of the reinforced concrete structure wall.
The wall modeling parameters are presented in Table 1.
Table -1: Properties of Wall/ Slab [1]
Young’s modulus (E) 2.3x107 kPa
Axial stiffness ( EA ) 6.9 x 107 kN/m
Flexural regidity ( EI ) 5.1759 x 107 kN/m2/ m
Equivalent thickness ( deq ) 3 m
Weight ( w ) 5 kN/m/m
Poisson’s ratio 0.3
Rayleigh α 0.01
Rayliegh β 0.01
2.1.2 Soil Modeling
In the present numerical analysis the soil has been modeled
using the hardening soil model, incorporated into the plaxis
program, considered in drained conditions.Table 2 gives the
properties of sand is used as both backfill material as well as
foundation soil.
Table -2: Properties of Sand [1]
2.1.3 Dynamic Analysis:
Dynamic analysis carried out after the static analysis taking
earthquake input motion. Dynamic analysis is same as
static analysis in addition to those earthquake boundary
conditions should be considered. Following are the
UPLAND earthquake details considered for the analysis.
Fig-5: Input accelertation time history of upland
earthquake
Upland Earthquake (Southern America,28/2/ 1990)
Peak ground Acceleration : 0.245 g
Duration of Earthquake : 10 sec
Local magnitude : 5.40
Epicentral distance : 5km
2.2 MODEL 2: Analysis of L-Shaped Retaining Wall With
Expanded Polystrene
Fig -6: Geometry and Boundary conditions

Fig -7: Deformed mesh
Numerical analysis is carried out for this model is same as
model 1. Boundary conditions and properties of soil and
slab/wall are same as model 1. But in this case EPS 15 is
taken for the analysis and their properties are mentioned in
the Table 3. Deformation of wall shown in figure 7
Properties of EPS
Material Model : Mohr’s coulomb model
Material Type : Drained
Table -3 Properties of EPS [2]
EPS
type
Density
kN/m3
Cohesi
on, C
(kPa)
Angle
of
internal
friction,
∅(°)
Modulus
of
elasticity
E(kPa)
Poiss
on’s
Ratio
EPS15 0.15 33.75 1.5 2400 0.10
EPS20 0.20 38.75 2 4000 0.12
EPS30 0.30 62 2.5 7800 0.17
2.2.1 Effect of Thickness of EPS
Chart -1: Lateral Earth Pressure for varies EPS thickness
(t/H) ratio
Chart -2: Extreme displacement of wall for different
thickness of EPS
Chart 1 showsthat increasing the thicknessof EPS therewill
be a greater reduction of lateral earth pressure. Fromchart2
it is observed that displacements values decreases upto t/H
ratio 0.2 beyond those displacement value increases, since
self weight on foundation slab decreases. Hence EPS
thickness ratio upto 0.2 is efficient.
2.2.2 Isolation Efficiency of EPS For Varies Densities
Chart -3 Isolation efficiency of EPS
Ap = (change in wall force b/w rigid and EPS)/(peak wall
force without EPS)
Where, Ap = Isolation efficiency
Chart 3 represents the isolation efficiency of EPS. In this
study EPS15, EPS20, EPS30 has been used for analysis. The
result shows that lower the density of EPS, higher the
isolation efficiency.

Chart -4: Comparison of Lateral Earth Pressure
Chart -5: Horizontal Displacement of Wall
Chart -6: Vertical Displacement of Wall
Chart 4 represents the variation of static anddynamiclateral
earth pressure with and without EPS, it shows that by
providing EPS greater reduction of lateral earth pressure
takes place especially at the base of the wall due to its
compressible nature.
Chart 5 and Chart-6 represents the horizontal and vertical
displacement of wall respectively. When retaining wall is
provided with EPS, it reduces displacement wall both in
horizontal and vertical directions under both static and
dynamic cases.
3. CONCLUSIONS
When L-shaped Retaining wall is provided with EPS lateral
earth pressure on the wall can be reduced effectively,sothat
the displacement of the wall can also be reduced under both
static and dynamic cases.
By increasing the thickness of EPS earth pressure decreases
and it is efficient upto t/H ratio 0.2, beyond that wall
displacement increases.
Lower the density of EPS, higher the isolation efficiency.
REFERENCES
1. Rouili. A, Djerbib. Y, Touahmia. M,“Numericalmodelling
of an L-shaped very stiff concrete retaining wall”.
Journal of Sciencesand Technologie B-No 24, Dec.2005,
PP 69-74.
2. Amit Harihar padade and Mandal.J.N, “Behavior of
expanded polystyrene (EPS) Geofoam under Triaxial
Loading Condition” EJGE, vol.17, 2012, Bund.S
3. Saman Zarnani and Bathurst.R.J, “Numerical parametric
study of expanded polystyrene(EPS) geofoam seismic
buffers” Canadian Geotechnical Journal, Vol. 46, 2009,
pp. 318-338.
4. Towhata, I. Geotechnical Earthquake Engineering,
Springer ed, 2008.
5. Wilson, P., and Elgamal, A. “Large-scale passive earth
pressure load displacement tests and numerical
simulation”, ASCE Journal of Geotechnical and
Geoenvironmental Engineering,Vol.134,2010,pp.1634-
1643.
6. Yoshimichi Tsukamoto and Kenji Ishihara, “Use of
compressible expanded polystrene blocksand geogrids
for retaining wall structures”Japanese Geotecnical
society vol. 42, 2002, No. 4, 29-41.
7. Seed. H.B, Whitman. R.V, “Design of earth retaining
structures for dynamic loads”. Proceedings of specialty
conference on lateral stresses in the ground and design
of earth retaining structures, Ithaca, New York: ASCE,
1970, PP 103-147.

IRJET- Numerical Analysis of L-Shaped Retaining Wall with Compressible Expanded Polystrene Under Static and Dynamic Condition

More Related Content

What's hot (20)

Similar to IRJET- Numerical Analysis of L-Shaped Retaining Wall with Compressible Expanded Polystrene Under Static and Dynamic Condition (20)

More from IRJET Journal (20)

Recently uploaded (20)

IRJET- Numerical Analysis of L-Shaped Retaining Wall with Compressible Expanded Polystrene Under Static and Dynamic Condition