Pull out resistance in MSEW

1. INVESTIGATING THE PULLOUT RESISTANCE
OF SUITABLE FILL MATERIAL REINFORCED
WITH STEEL
MAIN SUPERVISOR: MR. RICHARD KIZZA
CO-SUPERVISOR: DR. GILBERT KASANGAKI
NAME REGN NO. STUDENT NO.
ADRIKO NORMAN 11/U/3 211001742
OTEMA SOLOMON GABRIEL 11/U/473 211000241

2. MSE structures are widely used in highway and Geo-technical works.
Advancement of MSE concept and technology continues for more efficient ,
cost effective retaining structures.
 Use of inclusions to improve performance of MSEW
 Performance of earth reinforced structures influenced by factors (e.g. water
content, length of reinforcement etc. )
 Pull-out study employed for safe design of MSEW
Research Problem
Poor attitude leading to a lack of adequate local experience, evident in few
locally implemented projects based on MSE concepts and their application.
Justification
 Need for increasing local experience to change attitude through research
and local implementation using available materials
 Cost effectiveness and technical advantages on its implementation
construction.

3. Main Objective
To investigate the pullout resistance of suitable fill material reinforced with
inextensible steel.
Specific Objectives
i. Selection and classify the test fill material.
ii. Perform a parametric study on both soil and reinforcement factors that
influence pull out resistance.
iii.Establish empirical relationship between pullout resistance and factors
influencing it.
Scope of Works
Sample pits were located within Makerere University Main Campus behind the
School of Food Science and Technology building.
 Tests to classify fill material and determine its engineering properties.
 Parametric study of pullout resistance against selected factors that influence
it.
 Use of multiple regression analysis (SPSS) to analyze results.

4.  Soil reinforcement triggered by need for cost savings, simple
and fast construction, seismic performance, aesthetics and
settlement(Abu et al,2001)
 Lajevardi (2013) noted many materials used in reinforcing soil
i.e Extensible and inextensible. The use of inextensible steel
to stabilise earth structures is rapidly growing.
 The stability of earth structures depends on the soil
/reinforcement interaction (Ju et al, 2004)
 Stresses are transferred between soil and reinforcement by
friction and/ or passive resistance depending on
reinforcement geometry. (FHWA, 2001)
 A pull-out test allows to simulate the tensile stress applied on
the reinforcement and to define the evolution of the interface
parameters during its mobilization (Lajevardi, 2013)

5.  Fill material selection and preparation
 Laboratory soil classification tests based on
ASTM standards
 Development of physical model
 Pull out study based on Test Program between
selected factors and Pullout Resistance.
 Analysis of results and generation of an empirical
relationship using Multiple Regression Analysis in
SPSS.

6. For each of the soil classification tests, three separate tests were
performed in the laboratory and an average of soil properties obtained.
A summary of the soil properties is shown in the table below
Cohesion, C
(kPa)
Angle of
Internal
Friction,
PL (%) LL
(%)
PI
(%)
Specific
Gravity
OMC MDD, kg/m3 Cu Cc Gradation
10.096 39.5° 23.3 48.7 25.4 2.72 5.73% 2132.67 8.87 1.97 GW-GC
0
10
20
30
40
50
60
70
80
90
100
0.01 0.10 1.00 10.00 100.00
PercentagePassing(%)
Sieve Size (mm)

7. 30
40
50
60
70
80
90
100
15 25 35 45
MoistureContent(%)
Number of Blows
LIQUIT LIMIT
R² = 0.9665
R² = 0.9993
1900
2000
2100
2200
2300
2400
2500
1.00 6.00 11.00
DryDensity,kg/m3
Moisture Content , %
MDD 2122 Kg/m3
OMC 5.7 %
y = 0.827x + 10.096
R² = 0.9689
0
20
40
60
80
100
120
140
0 50 100 150
Shear Stress
Normal Stress, kPa
Graph of Shear Stress Vs Normal Stress
Series1
Linear
Direct Shear Test
The cohesion intercept of 10.096kPa and an angle
of internal friction of 39.5° were obtained.
According to Anderson et al(2010), a friction angle of
˃=34° is suitable for use in MSE Wall design. Hence
the material selected satisfies specification

8. Pullout Study
 A surcharge load of 81.67N/m2
was used for the pullout tests.
 An initial load of 6kg was added
to the bucket to strain the bar in
contact with the soil.
 The pullout force was measured
at 0.75 inches (20mm) of
displacement.
Scope of the Test Program
 The test program included a
total of 36 tests.
 Only straight pullout tests were
conducted during the research
study.
Pullout Matrix
Pullout
Test
Schematic
Description of
Compaction
Surcharge
Application
Detail (Straight Pullout) Number
of Tests
Reinforcement
Description
Embedded
Length
Diameter
(CSA)
95% degree of
compaction
(DOMC)
Loading
condition
Ribbed 300mm,
350mm, 400mm
4.5mm, 6mm,
10mm
9
Smooth 300mm,
350mm, 400mm
4.5mm, 6mm,
10mm
9
95% degree of
compaction
(WOMC)
Loading
condition
Ribbed 300mm,
350mm, 400mm
4.5mm, 6mm,
10mm
9
Smooth 300mm,
350mm, 40mm
4.5mm, 6mm,
10mm
9
Total 36

9. Results and Discussions
Pullout Resistance Versus
Surface Roughness
Ribbed bars had higher pullout
resistance values as compared to
smooth bars for all values of length
and diameter.
Pullout Resistance Versus
Moisture Content
Pullout resistance values were
higher on the DOMC than on the
WOMC.
Pullout Resistance Versus Length of
Embedment
 The values of pullout resistance
increased as the length of the bar
increased.
 Pullout resistance values for ribbed bars
were higher than those for smooth bars.
Pullout Resistance Versus Contact
Diameter
 The values of pullout resistance
increased as the diameter of the bars
increased.
 Pullout resistance values for ribbed bars
were higher than those for smooth bars.

10. R² = 0.9999
R² = 1
R² = 0.9999
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
200 300 400 500
PulloutResistance(kN)
Embedded Length (mm)
Pullout Resistance Vs Embedded Length (Ribbed Bars
of Varying Diameters DOMC)
Diameter 4.5mm
Diameter 6mm
diameter 10mm
Diameter (4.5mm)
Diameter(6mm)
Diameter(10mm)
R² = 0.9791
R² = 1
R² = 0.9985
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
250 350 450
PulloutResistance(kN)
Embedded Length (mm)
Pullout Resistance Vs Embedded Length (Ribbed
Bars of Varying Diameters WOMC)
Diameter(4.5mm)
Diameter(6mm)
Diameter(10mm)
Diameter(4.5mm)
Diameter(6mm)
Diameter(10mm)
R² = 1
R² = 1
R² = 1
-0.1
0.1
0.3
0.5
0.7
0.9
1.1
1.3
1.5
3 5 7 9 11
PulloutResistance(kN)
Diameter(mm)
Pullout Resistance Vs Diameter (Ribbed Bars of
Varying Embedded Length DOMC)
Embedded
Length(300mm)
Embedded
Length(350mm)
Embedded
Length(400mm)
Length(300mm)
Length(350mm)
Length(400mm)
R² = 0.9993
R² = 0.9918
R² = 0.9976
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 5 10 15
PulloutResistance(kN)
Diameter (mm)
Pullout Resistance Vs Diameter (Smooth Bars of
Varying Embedded Length DOMC)
Embedded
Length(300mm)
Embedded
Length(350mm)
Embedded
Length(400mm)
Length(300mm)
Length(350mm)
Length(400mm)

11. Correlations Pullout Resistance Versus Diameter
Pullout Resistance Versus Length
 Weak positive relationship between
Pullout Resistance and Length
r=0.229 significant at 0.1 level
 Strong positive relationship between
Pullout Resistance and Diameter
r=0.575 significant at all levels

12. Summary of Predictive Model
Table of Coefficients
Regression Model,
𝒀 = −𝟎. 𝟕𝟑𝟖 + 𝟎. 𝟎𝟕𝟏𝑿 + 𝟎. 𝟎𝟎𝟐𝒁
Where Y= Pullout Resistance (kN), X= Diameter (mm) and Z= Embedded
Length (mm).

13. Conclusions and
Recommendations
Conclusions
 The material was GW-GC
 Pullout resistance values were higher
on the DOMC as compared to the
WOMC
 Ribbed Bars generated a higher pullout
resistance as compared to Smooth Bars.
 The Pullout Resistance increased as
the length of embedment increased.
 Pullout Resistance increased as the
diameter increased.
 A high positive relationship between
Pullout Resistance and Diameter as
compared to Embedded Length.
 Contact Diameter was found to have a
more statistically significant
contribution to the predictive model as
compared to embedded length
Recommendations
 A method of quantifying the roughness
of the bars be developed and included in
the regression model.
 A larger sample size to improve the
accuracy with which the regression model
predicts the pullout resistance
 A proper silo loading mechanism should be
designed catering for factors such as angle
of friction of the sand particles and angle of
friction between the sand and the silo
material.
 Independent check analyses such as
Finite Element Modeling.
 Further research on all variables that
affect pullout resistance (Normal Stress,
Moisture Content, Soil type, bar spacing,
Depth of Fill, Overburden Stress Ratio,
etc.)
 Further study should be also be carried out
for different soil types.

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Highway and Transportation Officials, Washington DC
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Guidelines For MSE Walls with Independent Full Height Facing Panels.
 Anderson, P.L., Gladstone ,R.A., and Sankey, J.E. (2010) .State of the Practice of MSE Wall
Design for Highway Structures
 Andrew Garth, Sheffield Hallam University, 2008. Analysing Data using SPSS
 ASTM test designations D3080- (Direct Shear Box test), D 1557 -(Proctor Test), D 2487 -( Sieve
Analysis), D4318- (Atterberg Limits), D854-98- ( Specific Gravity)
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 Bobet Antonio.(2002). Design of MSE Walls for Fully Saturated conditions, Final Report, School
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 FHWA (2001). Mechanically Stabilized Earth walls and Reinforced Soil slopes Design and
Construction Guidelines, Publication No.FHWA-NHI-00-043
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by pullout tests, 40:48-57
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meeting
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