BEHAVIOUR OF A MODEL MV PILE IN SAND BEARING CAPACITY IMPLICATIONS JOHN EVELYN GUY A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science in Engineering. O JOHANNESBURG, 198 7
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BEHAVIOUR OF A MODEL MV PILE IN SAND
BEARING CAPACITY IMPLICATIONS
JOHN EVELYN GUY
A dissertation submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, in
fulfilment of the requirements for the Degree of Master
of Science in Engineering.
O
JOHANNESBURG, 198 7
DECLARATION
I declare that this dissertation is my own, unaided work.
It is being submitted for the Degree of Master of Science
in Engineering in the University of the Witwaterz: and.
Johannesburg. It has not been submitted before tor r 4
degree or examination in any other University.
(Signature of Candidate)
~7~n day of o & r~n 19»
(iii)
ABSTRACT
This report presents the results of a model MV pile test
conducted in ‘-.he laboratory and provides data on
measurements of the displacement of sand around the base
of the pile, as veil as o^ the loud distribution down
the pile during testing and installation. T ’se experi
ments were conducted in an attempt to cldtily some
the bearing capacity characteristics of the MV pile.
This is a driven displacement grouted in situ pile
formed by using a mandrel to drive an over-sized pile
shoe, the void behind the shoe being continually
supplied with grout.
During tne experiment, a 60 mm diameter semi-circular
half pile was driven into a steel box filled with an
approximately homogenous dense sand placed by a
"raining" technique. Tne pile was installed with the
sand submerged in water and with the flat face of the
semi-circular pile shoe lying against a glass panel
which formed one side of the sand box. Loads in the
pile shaft were measured during pile installation and
subsequent static load testing by strain gauges located
in the drive mandrel. Photographs of the soil around
the base of the pile were obtained at small penetration
(iv )
increments and the displacement components of individual
grains measured using a Wild A7 stereoplotter. Detailed
contour diagrams of the soil displacements and the
associated strain components are presented and discussed.
It was found that the lateral eurth pressure
cc—efficients applicable to the shaft friction capacity
approached those of the passive lateral earth pressure
co-efficienLs. The possible slip-line field arouid the
pile toe was found to differ significantly from that
conventionally assumed in the theoretical determination
of the bearing capacity factory, Nq. It was found
instead to resemble that indicated by an analysis of the
expansion of a cavity in an elastic solid. A possible
explanation for the reduction of shaft friction capacity
near a pile toe, referred to in the literature as an
"arching" effect, may be due to slip lines originating
at the pile toe interfering with those originating at
the pile shaft.
A preliminary proposal for a design method for MV piles
is presented on the basis of the model test results and
selected fieLJ test results.
( V)
ACKNOWLEDGEMENTS
Many people have been involved in the completion of this
report. To all of them, I wish to record my heartfelt
gratitude for their lielp, support, encouragement and
advice. Special mention should be made of tne fr_lowing:
The workshop and technical staff of the Department of
Civil Engineering for their never failing good humour
and companionship. In particular, Vince Newey and
Bernie de Bernier - craftsmen both.
Professor J M Ridley and Dr G S Wells of the Department
of Mathematics for their co-ordinate transformation
techn ique.
My colleagues at Grinaker Dura Piling who have
uncomplainingly tolerated the additional workload they
have had to carry during my absences. Special thanks to
Nico Maas, Brian McCartney and Chris Long.
Michel Antelme and his colleagues who graciously and
patiently allowed me free rein in the use of their Wild
A7 stereoplotter.
Dr Irvin Luker , who aught me a great deal, ac-.isted me
in all stages o£ this work, and who always made time for
discuss ions.
Professor G E Blight for his support and patience.
Guntner MUller whose enthusiasm fcr unis project never
waned .
The Directors of Grinaker Dura Piling (Pty) Ltd for
their continued support and for permission to publish
this report.
The Directors of Grinaker Holdings (Pty) Ltd and, in
particular Mr Wouter de Villiers and Mr Jack Saulez, for
their considerable patience and support. Thank you.
Jean Campbell who cheerfully typed the text many times
over .
Finally, L would like to thank my wife Lynda, and
children Micnelle and Carol, for their encouragement and
stoic support.
Financial assistance was provided by the Grinaker Group
of Compan ies.
(vi)
TABLE OF CONTENTS
DECLARATION
ABSTRACT
ACKNOWLEDGEMENTS
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF PHOTOGRAPHS
1 INTRODUCTION
1.1 Historical
1.2 Pile Design
2 PILE DESIGN
2.1 Static Bearing Capacity Design
2.2 Dynamic Bearing Capacity Design
2.3 Empirical Pile Design
2.4 Comment on Pile Design
3 THE MV PILE
3.1 Description
3.2 Historical Development
3.3 South African Experience
(vi i )
Page
( ii )
(iii)
( v )
(vii)
(xii)
(xi v )
(xx.i )
1 . 1
1.11.3
2.1
2 . 1
2. 2
2.5
2.6
3.1
3.1
3.4
3.7
TABLE OF CONTENTS
DECLARATION
ABSTRACT
ACKNOWLEDGEMENT?
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF PHOTOGRAPHS
1 INTRODUCTION
1.1 Historical
1.2 Pile Design
2 PILE DESIGN
2.1 Static Bearing Capacity Design
2.2 Dynamic Bearing Capacity Design
2.3 Empirical Pile Design
2.4 Comment on Pile Design
3 THE MV PILE
3.1 Description
3.2 Historical Development
3.3 South African Experience
(vii)
Page
(ii)
(iii)
(v)
(vii)
(xii)
(xiv)
(xxii)
1.11 . 1
1.3
2.1
2.1
2.2
2.5
2 . 6
3.1
3.1
3.4
(viii)
4 EXPERIMENTAL APPARATUS AND TECHNIQUES 4.1
4.1 Introduction 4.1
4.2 Model Pile System 4.3
4.2.1 Details of the Sand Box 4.10
4.3 The Test Sand 4.12
4.4 Sand Placement Technique 4.14
4.5 Model Pile 4.18
4.6 Model Grouting System 4.13
4.7 Pile Loading System 4.21
4.8 Data Collection 4.23
5 EXPERIMENTAL RESULTS 5.1
5.1 Impact Installation 5.4
5.2 Static Load Testing 5.12
5.3 Summar y 5.23
6 DISCUSSION OF EXPERIMENTAL RESULTS 6.1
o.l Impact Installation Data 6.1
6.1.1 Wave Equation Analysis 6.6
6.1.2 Dvnamic Resistance and
Plle Depth 6 .14
6.1.3 Summar y 6.15
6.2 Sand Grain Displacement Diagrams 6.16
6.2.1 Soil Displacements during
Pile Installation 6.17
6.2.2 Soil Displacements during
Static Loading 6.24
6.2.3 Summar y 6.31
(ix)
6.3 Discussion of Static Load Tests
6.3.1 Comparison of Drained and
Submerged Test Results
6.3.2 Comparison of Submerged ana
Post-Installation Load Test
Results
6.3.3 Shaft Friction Capacity
6.3.4 Elastic Recovery at End of
Static Load Test
6.3.5 Submerged and Drained Test
Sand C pacities
6.3.5 Summary
6.4 Soil Strain Analysis
6.4.1 Introduction
6.4.2 Symmetry in the Strain
Diagrams
6.4.3 Soil Strains During Pile
Instalia' n
6.4.4 Soil Strc s During Static
Load i ng
6.4.5 Summary
7 INTERPRETATION OF MODEL TEST RESULTS
7.1 t ntroduction
7.2 Shaft Friction
7.3 Toe Resistance During Static Loading
7.3.1 Limiting Equilibrium Models
and Model Test Observations
6 .32
6.33
6.35
6.36
6.41
6 .43
6.44
6.46
6.46
6.51
6.52
6.57
6.61
7 .1
7.1
7.2
7 . 12
7 . 14
(x)
7.3.2 Bearing Capacity Factory, Nq,
for the Model Pile 7.19
7.4 Comparison with Field Tests 7.22
7.5 Summary 7.25
8 SUMMARY AND RECOMMENDATIONS FOR FURTHER
WORK 8 . 1
3.1 Summary 8.1
8.2 Recommer.dations for Further Work 8.4
9 REFERENCES
10 APPENDICES
APPENDIX A A .1
A.l Measurement of Grain Displacements A.l
A . 2 Co-ordinate Transformation A.6
A . 3 Data Accuracy A . 11
A.4 Accuracy of Displacement Contour
Diagrams A . 25
A . 5 Axial Symmetry in the Model System A . 29
APPENDIX B B.l
B.l Dijv>ns ional Analysis B.l
B.1.1 Dynamic Analysis B.l
B.1.2 Static Analysis B.2
APPENDIX C
Typical Computer Printout of Wave
Equation Analysis C.l
appe*:1 x n n.l
Calculation cl Soil Strains D.l
APPENDIX E E.l
F.l Significance of the Load Data E.l
E.2 Friction Between Pile Shoe and
Glass E.2
E .3 Friction Between Plastic Separator
and Glass E.8
E.4 Friction Between Pile Shaft and
Glass Panel E. 11
(xi)
( X ’ i)
TABLE 5.1
TABLE 5.2
TABLE 5.3
TABLE 6.1
TABLE 6.2
TABLE 6.3
TABLE 6.4
TABLE 6.5
LIST OF TABLES
Summary of information gather during installation and load testing of the model pile
Load/Settlement records for the static load test on the pile in submerged sand
Load/Settlement records for the static load test on tte pile in drained sand
Data used in the wave equation analys is
Wave equation analysis results
Calculated displacement components for sand grains lying in contact with the pile s ioe during impact penetration
Calculated displacement components for sand grains lying in contact with the pile shoe during static load ing
Measured ( ) and corrected shear stresses at mid-points of strain gauge groups. Load test in submerged sand
Page
5 .2
5 . 19
5 .19
6 .3
6 . 1 1
6.23
6 .30
6.33
(xi i i)
TABLE 7.1
TABLE 7.2
TABLE 7.3
TABLE 7.4
TABLE A . 3
Measured ( ) and corrected shear stresses at mid-points of strain gauge groups. Load test in drained sand
Friction stress soil parameters determined by equation (7-1) Load test in submerged sand (for L4 load increment)
Friction stress soil parameters determined by equation (7-1).Load test in drained sand (for L8 load increment)
Friction stress soil parameters from equation (7-1) related to grout pressure. Load test in submerged sand (for L4 load increment)
Summary of some MV pile test load data. Compression tests
.1 A summary of measurement dataaccuracy for both control points and sand grains
6.38
7.6
7.6
7.7
7.23
A. 22
(:; i v )
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
LIST OF FIGURES
.1 General arrangement of some MV pile types
.1 Details of the model pile test n g- leader and pile
.2 Details of the model pile test rig- sandbox
.3 Details of the model pile - mandrel ana shoe
.4 Test sand, particle grading curves
.5 Relationship between fall heightand resulting soil density achieved with the sand rainer
.6 Details of the sand rainer
.7 Details and principle of the sand ra iner
.8 Details of the electrical instrumentation of the model pile
.9 Sketch diagram showing the camera, pile, soil and reference grid arrangements
.10 Measurement of sand grain displacements in the Wild A7 Autograph
3.2
4.6
4.7
4.8
4. 13
4.13
4. 16
4.17
4.24
4.28
4.28
(XV)
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE 5
FIGURE
FIGURE 5
'.1 Dynamic aata recorded during pileinstallation. (Refer to Plate 5.1b)
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