LABORATORY MODEL TESTS TO EFFECT OF DENSITY TO FILL MATERIAL ON THE PERFORMANCE OF A MODEL REINFORCED SOIL WALL

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 7, Issue 3, May–June 2016, pp. 365–372, Article ID: IJCIET_07_03_037
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LABORATORY MODEL TESTS TO EFFECT
OF DENSITY TO FILL MATERIAL ON THE
PERFORMANCE OF A MODEL
REINFORCED SOIL WALL
Sriharsha. Baditala
Assistant Professor, Department of Civil Engineering,
Assosa University, Assosa, Ethiopia
Yohannes Feyissa Beyisho
Dean for engineering and technology faculty,
Assosa University, Assosa, Ethiopia
ABSTRACT
The effective functioning of reinforced earth structures is very much
dependent on the quality of materials and construction. Many times, due to
poor quality of the materials used and poor quality control measures
exercised, the density of the reinforced soil fill is not up to the design
requirements, leading to underperformance or distress of the reinforced soil
walls. Therefore, it becomes necessary to evaluate the level of
underperformance vis-à-vis that of relative compaction. In view of this, in the
present study, a series of laboratory experiments were carried out on a model
soil wall of 300 mm high with vertical face, prepared at different density states
of 95%, 80% and 70% of MDD of IS HCT. The wall was subjected to
monotonic load applied through a model square footing of size (B) equal to 50
mm on the surface at an offset distance of 1(B). Similar tests were carried out
on the soil wall reinforced with a Woven Geotextile in wrap around form; to
study the effect of density on the performance of reinforced soil wall. The
results indicated proportionality between relative compaction level and
performance of soil wall without and with reinforcement.
Key words: Reinforced Earth Structures, Density of Soil Fill, Relative
Compaction, Offset Distance
Cite this Article: Sriharsha. Baditala and Yohannes Feyissa Beyisho,
Laboratory Model Tests To Effect of Density To Fill Material On The
Performance of A Model Reinforced Soil Wall. International Journal of Civil
Engineering and Technology, 7(3), 2016, pp.365–372.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=7&IType=3

Sriharsha. Baditala and Yohannes Feyissa Beyisho
1. INTRODUCTION
Tremendous increase in infrastructure development in India during the past decade
has increased the reinforced soil applications manifolds. Apart from design, the
effective functioning of these reinforced soil walls (RSW), is also dependent on the
quality of materials used and the control on quality exercised during construction.
Any slackness on these two issues results in low relative compaction, which in turn
results in underperformance or distress of the reinforced soil walls. It is a known fact
that, remediation of such walls adds to cost and affect project completion schedules. It
is therefore necessary to understand the role of in-situ dry density of the reinforced
soil fill on the performance of reinforced soil walls, such that, the performance of the
reinforced soil fill can be predicted in advance. Essentially, efforts are made in this
study, in this direction.
1.1. Review of Literature
Considerable research has been carried out on the behaviour of reinforced soil walls.
Juran, I. and Christopher, B., (1988), studied the behavior of soil wall reinforced with
different materials viz., woven polyester, geo-textile strips, plastic grids, and non-
woven materials. Ho, S.K., and Kerry Rowe, R., (1996), studied the effect of
geometric parameters. Vafaeian, M. and Abbaszadeh, R., (2008), have studied model
studies on soil wall reinforced with three types of cotton papers. They studied the
effect of tensile strength of the reinforcement, the number of layers, the vertical
spacing, the offset distance of the load applied on the surface and concluded that, the
failure surface was found to be an arc of a circle when stiffer reinforcement is used
and that for weaker reinforcement was almost a straight line. They also concluded
that, the performance of the RSW was better when tensile strength of the
reinforcement was higher and number of reinforcement layers was higher. However,
limited studies were carried out on the effect of density on performance of RSW,
which has been addressed in the present study.
2. METHODOLOGY
The methodology includes collection and characterisation of the materials;
performing monotonic load tests; analysis and interpretation of test results and
drawing observations and conclusions.
2.1. Characterization of Silty Sand
The Silty Sand used in this study (locally called as Morum) is collected from
Mahaboob nagar district of Telangana state. The index and engineering properties of
soil are summarised in Table 1.
Table 1 Properties of Silty Sand
Parameter Value
Gravel sized particles 16.4 %
Sand sized particles 78%
Fine grained particles 5.6%
Consistency Non plastic
MDD (IS HCT) 2.03 g/cc
OMC (IS HCT) 9.60 %
Classification
(IS:1498-1970)
SP

Laboratory Model Tests To Effect of Density To Fill Material On The Performance of A
Model Reinforced Soil Wall
2.2. Characteristics of Woven Geotextile
The woven geotextile used in this study is shown in Fig. 1 and its characteristics are
indicated in Table 2
Figure 1 A view of the woven geotextile
Table 2 Characteristics of Woven Geotextile
Property Value
Type of geosynthetic
Polypropylene slit filmtape woven
geotextile
Commercial name SKAPS W-250
Mass per unit area 170 (g/sqm)
Thickness 0.425 (mm)
Grab Tensile strength 1.11 (kN)
Grab elongation 15 (%)
Puncture resistance 4.005 (kN)
2.3. Test set up
The experimental test set up is shown in Fig 1. The PC controlled Tri-axial test
facility is utilised to conduct the model plate load tests. The application of load is by
hydraulic control system and the load is measured by an electronic load cell with a
sensitivity of 1 kg. The settlement is measured by electronic Linear Voltage
Differential Transducer (LVDT) of ± 50 mm range. The PC controlled facility is run
by software that enables to give the operating conditions as input. The facility logs the
load and settlement observations continuously and provides online display of the
progress of the mechanism.
Figure 2 A view of the test set up

2.4. Model test tank & Model footing
A model test tank of size 300mmx750mmx600mm is used. The tests are carried out
using model footing of size 50 mm such that the width of the tank 300 mm and depth
300 mm, will be more than or equal to 5B, such that the boundary effects are avoided.
The model footings are made of 25mm thick aluminium plates with a rough base.
2.5. Scheme of experiments
The investigations are carried out systematically as per the scheme of experiments,
which includes determining the resistance to the load applied at an offset distance of 1
(B), on the soil wall prepared at three different relative compactions viz., 70%, 85%
and 95% ; without and with woven geotextile in wrap around form.
3. RESULTS
3.1. Pertaining to un-reinforced soil wall
The results of monotonic load tests on un-reinforced soil wall represented in terms of
bearing pressure versus settlement are presented in Fig. 3 and the typical failure is
depicted in Fig. 4.
Figure 3 Variation in Bearing Pressure with Settlement pertaining to Unreinforced Soil Wall
Figure 4 A view of failure of Unreinforced Soil Wall at 70% relative compaction, with load
applied at an offset distance of 1B
0
50
100
150
200
250
300
350
0 2 4 6 8 10
BearingPressure(kPa)
Settlement
70% relative compaction

3.2. Pertaining to reinforced soil wall
The results of similar monotonic load tests carried out on soil wall reinforced with
woven geotextile in wrapped around form ; compacted at three specified relative
compactions; subjected to the load applied at an offset distance of 1.0 B ; is presented
in Fig. 5 and a typical view of failure is shown in Fig. 6.
Figure 5 Variation in Bearing Pressure with Settlement pertaining to Reinforced Soil Wall
Figure 6 A view of failure of the reinforced soil wall at a relative compaction of 70%, with
load applied at an offset distance of 1B
4. OBSERVATIONS
4.1. Pertaining to unreinforced soil wall
Based on the analysis of test results pertaining to monotonic load tests on
unreinforced soil wall, the following observations are made:
1. As it can be seen from Fig. 3, the nature of bearing pressure versus settlement curve,
in general is elasto-plastic. A closer examination reveals the fact that, complete
failure without considerable plastic deformation was observed specifically at lower
relative compaction of 70%.
2. As depicted in Fig. 4, the mode of failure included separation and collapse of plastic
zone formed on the unsupported vertical face. The rupture surface was found to be
curvilinear akin to a paraboloid.
3. The variation in resistance against applied loads with variation in relative compaction
is presented in Fig. 7. It can be seen that, higher the relative compaction, higher is the
0
500
1000
1500
2000
2500
3000
0 5 10 15 20 25 30
BearingPressure(kPa)
Settlement (mm)

resistance offered against the applied load. The relationship is well represented by a
second order polynomial or by a power equation.
Figure 7 Variation in Bearing Pressure at failure with Relative Compaction pertaining to
Unreinforced Soil Wall
4.2. Pertaining to Reinforced soil wall
The observations pertaining to the reinforced soil wall are as presented below:
1. The nature of bearing pressure versus settlement curve, for reinforced soil wall, is
also elasto-plastic, as seen in Fig. 5. Interestingly, when reinforced, complete failure
was not observed even at lower relative compaction of 70%.
2. As shown in Fig. 6, the reinforced soil wall sustained deformation, but not undergone
complete failure, as it happened in unreinforced soil wall.
3. As it can be observed in Fig. 8, resistance to the applied load is increasing with increase in
relative compaction. The relationship is well represented by 2nd
order polynomial as well as
power equation; similar to that for unreinforced soil wall.
Figure 8 Variation in Bearing Pressure at failure with Relative Compaction pertaining to
Reinforced Soil Wall
y = 11.906x - 856.59
R² = 0.9338
y = 4E-25x13.647
R² = 0.9725
y = 0.4636x2 - 64.954x + 2279.5
R² = 1
y = 6E-05e0.1647x
R² = 0.9569
-50
0
50
100
150
200
250
300
350
400
60 70 80 90 100
BearingPressureatfailure,kPa
Relative Compaction, (%)
y = 59.029x - 4076.3
R² = 0.9529
y = 4E-12x7.3667
R² = 1
y = 1.9187x2 - 259.07x + 8902.8
R² = 1
y = 0.3333e0.0895x
R² = 0.9978
0
200
400
600
800
1000
1200
1400
1600
1800
60 70 80 90 100
Relative Compaction, (%)

4.3. Observations pertaining to general comparison
The behaviour of unreinforced and reinforced soil wall is compared one-to-one and
the following observations are drawn:
1. It is clearly seen from Fig. 9 that, at any relative compaction, a definite increase in
resistance offered against the applied load is seen when the soil wall is reinforced.
Figure 9 Comparison of Bearing Pressure at failure soil wall with and without reinforcement
1. The variation of percentage increase in the resistance with relative compaction, is
shown in Fig. 10. As established in earlier research, weaker the soil, higher is the
percentage increase when reinforced.
Figure 10 Variation of Percentage increase in Bearing Pressure at failure due to
reinforcement
5. CONCLUSIONS
Based on the experimental investigations carried out in this study, the following
important conclusions are drawn:
1. This study clearly established that, higher the dry density of the fill material, higher is
the resistance offered against the applied loads. This was observed in both
Unreinforced Soil Wall and Reinforced Soil Wall.
0
200
400
600
800
1000
1200
1400
1600
1800
70 80 95
Un-reinforced Soil Wall
Reinforced Soil Wall
Relative Compaction,(%)
0
1000
2000
3000
4000
5000
70 80 95
Percentageincrease
Relative Compaction (%)

2. A definite increase in resistance to the applied loads was observed when soil wall is
reinforced. For the materials used and for the test conditions adopted in this paper, the
increase was in the range 449 % to 3827 %. This emphasizes the importance of
reinforcement in soil walls.
3. The mode of failure in Unreinforced Soil Wall was consisting of separation and
collapse of a zone of soil near the face of wall. This was contained when reinforced.
Hence, this study showed that, collapse of soil wall can be effectively contained when
reinforced.
4. On the whole, this study clearly brought out the mechanisms of failure of soil walls
when subjected to applied loads without and with reinforcement. This study is useful
to the designers and practitioners in prediction of the impact of under compaction on
the behavior of reinforced soil wall.
REFERENCES
[1] Ashmawy, A.K. and Bourdeau, P.L., (1995), Geosynthetic Reinforced Soils
under Repeated Loading: A Review and Comparative Design Study,
Geosynthetics International, 2(4), pp.643–678
[2] Lee, K. L., Adams, B. D. and Vagneron, J. M. J, Reinforced Earth Retaining
Walls, ASCE, Vol. 99, No. SM10, (1973), pp.745–764.
[3] Juran, I. and Christopher, B., Laboratory Model Study on Geosynthetic
Reinforced Soil Retaining Walls”, J. of Geotech. and Geoenv. Eng., ASCE,
115(5) 1988, pp.905–926.
[4] Vafaeian, M. and Abbaszadeh, R., Laboratory Model Tests To Study The
Behavior of Soil Wall Reinforced by Weak Reinforcing Layers, IJE, 21(4) Dec
2008, pp.361–374.
[5] Bathurst, R.J., Nernheim, A., Walters, D.L., Allen, T.M., Burgess, P., and
Saunders, D.D, Influence of reinforcement stiffness and compaction on the
performance of four geosynthetic-reinforced soil walls, Geosynthetics
International, 16(1), pp.43–59
[6] Ho, S.K., and Kerry Rowe, R., Effect of wall geometry on reinforced soil walls”,
Geotextiles and Geomembranes, 14(10) Oct-1996, pp.521–541.
[7] Binquet, J., and Lee, L.K., (1975), Bearing Capacity Tests on Reinforced Earth
Slabs, Journal of Geotechnical Engineering Division, ASCE, 101(12), pp.1241–
1255.
[8] Sridharan, A., Srinivasamurthy, B R., Bindumakhava., and Vasudevan, A K.,
Reinforced Soil Foundation on Soft Soil, Geotextile Conference, (1988),pp. C53-
60
[9] K.V. Maheshwari, Dr. A.K. Desai and Dr. C.H. Solanki, Bearing Capacity of
Fiber Reinforced Soil. International Journal of Civil Engineering and
Technology, 4(1), 2013, pp.159–164.
[10] Machhindra S.Purkar and Sunil Y. Kute, Numerical Modeling of Reinforced Soil
Segmental Wall under Surcharge Loading. International Journal of Civil
Engineering and Technology, 4(1), 2013, pp.1–15.

LABORATORY MODEL TESTS TO EFFECT OF DENSITY TO FILL MATERIAL ON THE PERFORMANCE OF A MODEL REINFORCED SOIL WALL

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