BEHAVIOUR OF A MODEL MV PILE IN SAND BEARING CAPACITY ...

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





3 THE MV PILE

3.1 Description

3.2 Historical Development


(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)

.2 Horizontal (X axis) sand graindisplacements. Plates 1-2 Dynamic.

.3 Vertical (Y axis) sand grain displacements. Plates 1-2 Dynamic.

.4 Horizontal (X axis) sand graindisplacements. Plates 1-3 Dynamic.

.5 Vertical (Y axis) sand grain displacements. Plates 1-3 Dynamic.

.6 Load/settlement behaviour of the model pxie.

.7 Settlement/time data for the model pile tests showing when soil displacements were photographed.

.8 Load distribution down the pile shaft during load testing of the pile in submerged sand.

.9 Load distribution down the pile shaft during load testing of the pile in drained sand.

.10 Horizontal (X axis) sand graindisplacements. Plates 1-2 Static.

.11 Vertical (Y axis) sand grain dis-placements. Plates 1-2 Static.

5.5

Rear pocke t

5.15

5 .16

5 .17

5 .18

Rearpocket

(xvi)

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE 6

FIGURE 6

FIGURE 6

FIGURE 6


.13 Vertical (Y axis) sand graindisplacements. Plates 1-3 Static.


.15 Vertical (Y axis) sand graindisplacements. Plates 1-4 Static.

.16 Horizontal VX axis) sand graindisplacements. Plates 1-5 Static.

,'.7 Vertica' (Y axis) sand graindisplacements. Plates 1-5 Static.

.1 Mass/spring approximation of the model pile for the wave equation analys is

.2 Wave equation soil model

.3 Dynamic pile resistance plotted against pile penetration depth

.4 Sketch showing displacement of a sand grain remaining in contact with the pile shoe, and calculation of its displacement components

.5 Shear stress distribution down the pile shaft during the load test in submerged sand

Rea i pocket

it

ii

••

M

it

6 .7

o .10

6.15

6.23

6 .39

(xv i i)

FIGURE

FIGURE

FIGURE

FIGURE

FIGURf.

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

.6 Shear stress distribution down the oile shaft during the load test in drained sand

.7 Rectangular grid used to estimate pile installation soil strains

.8 Major principal strain contours at lOÛ-strain. Plates 1-2 Dynamic.

.9 Major principal strain directions. Plates 1-2 Dynamic.

.10 Minor principal strain contours at 10 u-strain. Plates 1-2 Dynamic.

.11 Circumferential strain contours at 10û-strain. plates 1-2 Dynamic.

.12 Maximum shear strain contours at 10û-strain. Plates 1-2 Dynamic.

.13 Volumetric strain contours at10û-strain. Plates 1-2 Dynamic.

.14 Major principal strain contours at lOû-strain. Plates 1-3 Dynamic.

.15 Major principal strain directions. Plates 1-3 Dynamic.

.16 Minor principal strain contours at 10 u-strain. Plates 1-3 ?/namic.

.17 Circumferential strain contours at10 u-strain. Plates 1-3 Dynamic.

6 .40

Rear pocke t

(xv i i i)

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGUKc

FIGURE

FIGURE

.18 Maximum shear strain contours at IQ"* u-strain . Plates 1-3 Dynamic.

.19 Volumetric strain contours at 10^ u- strain. Plates 1-3 Dynamic.

.20 Rectangular grid used to estimate soil strains during pile loading,

.21 Major principal strain contours at lOû-strain. Plates 1-2 Static.

.22 Major principal strain directions. Plates 1-2 Static.

.23 Minor principal strain contours at 103 u-strain. Plates 1-2 Static.

.24 Circumferential strain contours at 10 u-strain. Plates 1-2 Static.

.25 Maximum shear strain contours at I03u-strain. Plates 1-2 Static.

.26 Volumetric strain contours at 10Û- strain. Plates 1-2 Static.

.27 Major principal strain contours at lOû-strain. Plates 1-3 Static.

.28 Major principal strain directions. Plates 1-3 Static.

.29 Minor principal strain contours at1.0û-strain. Plates 1-3 Static.

Re at pocket

ii

•i

ii

ii

ii

ii

M

II

II

II

(xix)

FIGURE 6.30 Circumferential strain contours at 103 u-strain. Plates 1-3 Static.

FIGURE 6.31 Maximum shear strain contours at 103 u-strain. Plates 1-3 Static.

FIGURE 6.32 Volumetric strain contours at 10 3 u- strain. Plates 1-3 Static.

FIGURE 6.33 Major principal strain contours at 10ii-atrain. Plates 1-4 static.

FIGURE 6.34 Major principal strain directions. Plates 1-4 Static.

FIGURE 6.35 Minor principal strain contours at 103 u-strain. Plates 1-4 Static.

FIGURE 6.36 Circumferential strain tort ’t3 at10 u-strain. Plates 1-4 Static.

FIGURE 6.37 Maximum shear strain contours at 103 u-strain. Plates 1-4 Static.

FIGURE 6.38 Volumetric strain contours ~ t 103u- strain. Plates 1-4 Static.

FIGURE 6.39 Major principal strain contours at 103 u-strain. Plates 1-5 Static.

FIGURE 6.40 Major principal strain directions. Plate3 1-5 Static.

FIGURE 6.41 Minor principal strain contours at 10^u-atrain. Plates 1-5 Static.

FIGURE 6.42 Circumferential strain contours at103u-strain. Plates 1-5 Static.

Rearpocket

ii

II

II

II

• I

it

II

• I

II

II

II

(XX)

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

FIGURE

i’IGURE

6.43 Maximum shear strain contours at lO^u-strain Plates 1-5 Static.

6.44 Volumetric st: 'in contours at 10 u- strain. Plates 1-5 Static.

7.1 a possible slip-line field around the model pile.

7.2 Test sand shear strength data from triaxial tests.

A.l Sketch illustrating the mechanical arrangement of Wild A7 Autograph.

A.2 Sketch illustrating how the control points on the reference grid were co-ordinated in the Wild A7 Autograph

A.3 Geometrical relationships betweencontrol points located on correctly aligned and mis-aligned photographs

\.4 Illustrates the positions of control points on a mis-aligned photograph superimposed on a correctly alignedphotogr aph

\.5 Parabolic deflection of the glass pic. te

Rearpocket

ii

7 .16

7 .17

A .4

A .4

A. 7

A.7

A . 18

FIGURE A.6 Deflection of the glass plateapproximated as a rotated plane A . 13

(xxi )

FIGURE A.

FIGURE A.

FIGURE D.

FIGURE D.

FIGURE E..

FIGURE E.;

FIGURE A. 7 Section through film holder showing possi e distortion of a sheet of photographic film

Effect of image plane rotations

Graph showing the logarithm of the displacements plotted against distance from the pile shoe

Notation for deformation of a rectangular d e m e n t .

Use of contour diagrams to obtain displacements at nodes.

Summary of force end stress Components resisting penetration of the model pile

Summary of friction lo*d components in the grout column and on the pile sha £ t

A. 18

A. 20

A.30

D . 4

D.5

E. 3

E . 9

(xxi i )

PLA'iii 4.

PLATE 4.2

PLATE 4.3

PLATE 5.1

PLATE 5.2

PLATE 5.3

LIST OF PHOTOGRAPHS

General views . pile testing equipment and plate f;im camera.

Pile loading system.

Wild A 7 Autograph.

Showinq four osci1loscopu traces of impact records on the model pile during pile installation

Showing four oscilloscope traces of impact records on the model pile obtained at various depths while installing the pile during experiment No. 8.

Showing variour aspects of the model pile after removal from the sandbox.

4.5

*.22

4.27

5.7 &3.6

5.9 & 5 .10

5.21

1

1. INTRODUCTION

1.1 Histor ical

Piles perform their load carrying function by

transmitting the load applied at the pile head to the

underlying soils through skin friction on the pile shaft

and end bearing on the pile toe. Some piles generate

most of their load carrying capacity tnrougn shaft

friction - for example MV piles - and are therefore

suitable as "floating" or "friction" piles whereas

others, such as cased oscillator piles (eg Penoto

piles), are more suited for use as end bearing piles.

Generally, aach piling system is sufficiently different

in both installation technique and load performance for

different pile types of similar dimensions in the same

soil to develop significantly wide ranging load

capacities. Braadtvedt (1980) highlighted this point

when he stated that, depending solely on .nstallation

technique, the capacity of a pile of given dimensions

may vary by as much as a factor of six.

Piled foundations have been a recognised construction

technique for many centuries. "Certainly, as far back

as the time of Vitruvius we find piles being recommended

when a suitable foundation cannot be found by excavating?

the various lake dwellings in Europe provide examples of

still earlier use. In Arrian's Life of Alexander the

Great (Book II) a description is given of the use of

piles for the construction of the mole used for the

reduction of the city of Tyre (20th Aug., 332 3 C) "

(Little, [1961, p . 128]). Caesar, in De Bello Gallico IV

(translated by Handford [1951]} presents a detailed

description of the use of piled wooden piers for a

’-'t idge constructed across the Rhine river.

Piles were not uncommon in the foundations of medieval

structures. Little (1961, p.125), for example, mentions

the use of piles in the construction of Winchester

Cathedral (completed A D 1093) and Filarete (translated

by Spencer [1965]) describes how piles would be used for

construction of a oridge (Spencer, 1965 p.164 and 290).

The cover panels of Chellis' book "Pile Foundations"

(1961) present some excellent illustrations of medieval

and primitive pile driving equipment.

"Until somt time in the nineteenth century, wood piles

were the only common type; since then, steel, concrete

and composite piles of many kind have come into wide

use" (Taylor, 1948, p.640). It is not altogether clear

from the early literature what the exact sequence was in

either tne emergence of new pile tvpes or the development

of new installation and driving techniques. Poulos and

Davis (1980 p.l) suggest that, "Modern literature on

piles can be said to date from the publication of 'Piles

Page 1.2

and Pile Driving' edited by Wellington of the Eng j. leer ing

News ..... in 1893 .....". It is apparent, however,

that the period 1850 to 1950 saw a proliferation of pile

equipment and design techniques of large magnitude which

reflected the rapid industrial expansion of the period.

The industrialization of South Africa lagged somewhat

behind that of the northern hemisphere countries and it

was not until about 1938 that South A f r i c a ’s first

specialist piling contractor, McLaren and Eger, came

into existence.

1.2 Pile Design

Increasing cost and frequency of use of pile foundations

during the last century have obliged the foundation

engineer to develop methods to predict more accurately

and reliably the performance of the piles specified in

his design. " ..... until the late nineteenth century,

the design of pile foundations was based entirely o:

experience, or even divine providence." (Poulos and

Davis, op cit). Despite the considerable volume of

published literature on the subject, both practical and

theoretical research into pile performance parameters

have advanced hesitantly with the result that today pile

design still tends to be largely d e ^ n d e n t on empirical

data and thus on the experience of the designer.

Nevertheless, the design of a single pile foundation for

ultimate axial capacity is conveniently divisible into

Page 1.3

three major approaches which may be applied singly or in

combination. These include use o£ static bearing

capacity formulae, dynamic bearing capacity formulae and

empirical approaches ba ;ed on past experience and/or on

in situ test methods. Chapter 2 presents a brief review

of these topics.

This report presents the results of an attemp*. to obtain

data on both tne installation characteristics and ioading

benaviour of a laboratory scale model pile instai led m

Sind. The pile type used for this investigation was a

driven d l spl ace:nen t grouted in situ pile known as the MV

pile. Features of the MV pile are described in Chapter 3.

Page 1.4

1

2. PILE DESIGN


Static bearing capacity design methods attempt to

determine ultimate pile capacity by use of in situ soil

strength parameters. Typically, ultimate capacity, Qu,

is expressed as the sum of the ultimate shaft friction,

Os, and the ultimate toe resistance, Qb, (eg Bowies

1977 p.523),

Qu - Qs ♦ Qb (2-1)

wher e :

Qs * As (K. pv.tan ?) (2-2)

and:

Qb * Ab (>.b.Ny.S'r ♦ c.Nc.Sc. ♦ pv.Nq.Sq) (2-3)

for which As * surface area of the pile shaft: K « a

lateral earth pressure coefficient: pv » average

effective overburden pressure along the shaft: ? ■

friction angle between pile and soil; Ab *■ area of the

pile toe: y » effective unit weight of the soil at the

pile poir- • b * toe diameter; c ■ cohesion of the

soil; pv = effective overburden pressure at the pile

toe; and N y , N c , Nq « theoretical bearing capacity

factors related to the friction angle of the soil and on

assumed failure pattern; and Sv, Sc, and Sq are shape

factor s .

No single equation has been found to be adequate for ail

s i tuat ions.

Most of the standard foundation texts describe the use

of these equations in pile design. It is not certain

where or when the static bearing capacity design

approach originated, but it is apparent (Terzahi [1943],

p.137) that it had been proposed prior to 1910.


Estimation of driven pile capacity by consideration of

the dynamics 3f the lile/hammer system, has lead to two

different approaches. The first, and historically the

oldest invol/es a large family of "dynamic formulae” .

These are based on impulse-mome.ntum principles using

classical mechanics for which an energy balance equation

is established. The equation is usually expressed in a

form in which the pile "set" (penetration per hammer

blov.) required to ensure a particular pile capacity, can

be calculated. Bowles (1977, p.561) presents an in

depth review of how the detailed version of such an

equation termed the "rational pile formula", is derived.

The second approach to the determination of driven pile

capacity by dynamic methods, is based on a mathematical

^odel using the one dimensional wave equation for stress

transmission in elastic rods.

Page 2.2

Simplifications and assumptions applied to the "rational

pile formula" by various authors have led to the

publication of a large family of related dynamic

formulae, some of which d - U from the early 1300's.

Chellis (1961 Appendix 1) lists about forty different

versions, some of which ace also discussed by Bowles

(1977) and Taylor (1948). According to Smith (1960),

"... the editors of Engineering News Record have on file

lour hundred and fifty such formulae." Terzaghi (1943

p.141-142), basing his comments on a report by Cummings

(1940), expressed reservations about both the theoretical

basis of th_- impact equations and their applicability to

the pile/soil system. He comments as follows, "On

account of tneir inherent defects all the existing pile

formulas are utterly misleading as to the influence of

vital conditions, such as the ratio between the weight

of the pile and the hammer, on the result of the pile

driving operations." Despite the undeniable objections

to the theoretical basis of the dynamic formulae, they

have remained in popular use and have been incorporated

into various standards (eg SABS 088 [1972]).

A number of statistical studies into the reliability of

dynamic pile driving formulae have been undertaken.

Some of these include the Michigan State highway

Commission (1965), Olsen and Flaate (1967) and ASCE

(1946). Although a large amount of data was considered

in these analyses, no single preferred dynamic formula

Page 2.3

could be I rivint i f >ed. The better performers were found

to inclL--,<» ■ i Hiley, Janbu and Gates formulae.

Commenting cr. the ASCE (1941) report on their

investigation into pile driving formulae, Peck (1942)

was prompted to observe that a bearing capacity formula

of Qu = 91 tons was, for the recorded data, statistically

as accurate as the dynamic formulae used to predict

their capacity.

It appears chat the first to recognise the applicability

of the "wave equation" to the analysis of pile driving

was Isaacs in 1931. Fox (in Glanville et al, 1938) also

published a driven pile solution to the wave equation.

The design method given by these two authors, however,

was not widely adopted, mainly because of the tedious

calculation involved. Edward A. Smith of the Raymond

Concrete Pile Company provided the first tractable

application of the wave equation to driven piles.

Smith formalized his ideas in publications dated 1955 and

1960. A considerable amount of practical and theoretical

research into the wave equation and related methods have

since been carried out, particularly in America. The

first international conference on the application of

stress wave theory on pile3 was held at Stockholm in

June 1980 (Bredenberg [1980]). A state of the art review

of the wave equation and a list of the major research

publications was presented oy Goble et al (1980) .

Page 2.4

So.e " :cel]ent correlations between pile capacity

pre. d by the wave equation and measured failure

loads, have been reported (eg Goble et al [1975],

Rausche et al [1972], Forehand and Reese [1964]). Goble

et. al (1975) for example indicate an error range of —

10% from the predicted pile capacity. Other authors (eg

Lowery et al [1968], Ramey and Hudgins [1977]), found

that the error ranged up to as high as — 40% while

Tavenas and Audibert (1977) concluded that there was no

correlation at all between wave equation predictions and

measured pile performance. It must oe accepted therefore

that the wave equation, in common with otner pile design

techniques, has its limitations.


Empirical design by the installation and testing of

trial piles is relatively expensive. Consequently, only

contracts of reasonable size can justify the experimental

costs. Further, such experiments are time consuming and

require between three and five weeks to conduct.

Because empirical design by use of full scale field

tests is not generally justifiable, much effort has been

expended in developing alternative in situ test tech

niques. Most of these involve the use of penetrometers,

tho argument for their use being that the resistance to

penetration experienced by the penetrometer can be

Page 2.5

correlated to pile bearing capacity. Also in favour of

using penetrometers as a pile design tool, is that they

are frequently used in site investigation to obtain both

soil properties and an indication of the subsurface

prof ile.

Sanglerat (1972, 1979) has described in some depth, the

theory and practice related to many of the large variety

of both static and dynamic penetrometers in use around

the world. He aiso describes an equally large variety

of pile/penetrometer design correlations. As a method

of design, it would appear that the subject is little

better off than alternative methods. Amongst the many

penetrometer pile design techniques those of Van der

Veen and Boersma (1957), de Beer (1965) and Meyerhof

(1956, 1976) may be considered the most popular.

There is considerable potential in the use of penetro

meter data for the -sign of piles. Until penetrometer/

soil interaction is properly understood, and until some

technique is developed to extrapolate this information

in a rational manner to pile behaviour however, the

design correlations must remain empirical and subject to

uncer tainty.


Of the three main approaches to pile design, pile bearing

capacity determination by the use of "static" formulae

P aye 2.6

is considered the most i iportant method. The static

design approach is usually used in conjunction with, or

in suppott of the other design methods, and will

therefore be routinely used in most situations where the

need for piles is being considered. Considerable

reliance is therefore often placed on this metnod.

Static pile design, however, remains a largely empirical

science. In a succinct analysis of existing design

methods, Tomlinson (1977) has drawn attention to some of

the weaknesses of the design formula. In his analysis

Tomlinson makes the following comments:

"... the effects of the various methods of pile

installation on the carrying capacity and deformation

characteristics (of piles) cannot be calculated by

strict application of soil or rock mechanics theory".

(Op cit, p.li.) Consequently, calculation of the load

carrying capacity of piles, "... is based partly on

theoretical concepts ..., but mainly on empirical

methods based on experience". (Op cit, p.10.) Despite

the apparently scientific nature of pile design,

therefore "The overriding influence of experience and

the limitations of theory make piling practice an art

rather than a scien;e . . .". (Op cit, p. 11.) In an

attempt to reduce this dependence on experience as a

necessary component in pile design, various theocetical

and practical (laboratory and full scale) studies have

been carried out to investigate the parameters thought

Page 2 .7

to affect pile behaviour. Summaries of the findings of

the major full scale investigations can be found in the

standard texts. Theoretical studies into the behaviour

of piles are limited by the ap licability of the soil

models used in the analyses and by the availability of

suitable experimental data with which to compare the

theoretical findings. Some of the laboratory scale

studies which have been carried out, are discussed in

Chapter 4. As Tomlinson notes (op cit, p.11), however,

"Attempts to study the behaviour of piles in the

laboratory have not produced any worthwhile design rules

because of the impossibility of reproducing installation

effects in model piles. At best, they have given an

insight into the fundamental matters of the transfer of

load from the pile to the soil ...". Whilst reproduction

of pile installation effects using model piles may be of

limited value when extrapolating the findings to full

scale piles, it is suggested that model pile tests

constitute the most reliable way of investigating the

mechanism of pile/soil interaction and through this, of

obtaining improved design methods.

Page 2.3

1

3. THE MV PILE

3.1 Descr i pt ion

The MV pile .nay be described is a driven displacement

grouted in situ pile. The equipment generally comprises

a p . oversize pile shoe, a drive mandrel which may or may

not be a permanent fixture and a grouted annulus which

fills the cavity formed by the shoe between the soil and

the mandrel. Pile installation is achieved by dynamic

methods and use may be made of any of the pile driving

hammer techniques including a vibro-hammer. Usually

grout is pumped continuously to the pile toe during

driving. Figure 3.1 shows the general arrangement of

some of tne MV pile types which have been used in past

contracts.

Within th:s general arrangement for the MV piling system

a considerable variety of piles can be manufactured for

particular applications. Shaft diameter and shape are

determined by the diameter and shape of the pile shoe.

Complex shapes have been used to ensure panel inter

locking for contiguous pile walling. Typically the MV

pile shoes are made of manufactured plate steel box

structures or precast reinforced concrete elements.

The drive mandrel may be made from any dimensiona1ly and

structurally suitable steel section (including hollow

2

Re-usable steel dr ive m a r d r e l , d isposab le precas t concrete shoe in terna l grou t pipe

In te rn a ldrophammer

Grout pipe mani fo ld

PLAN nT BASE OF SHAFT

Gussets

Grout pipe

Permanent precast concrete s h a f t and in teg ra l shoe, i n te r n a l grou t pipe

Re-usable s tee l dr ive mandre l , d isposable base plate, i n te rna l drop hcmmer, external grou t p ipes ,expanded concrete base.

Permanent steel sha f t f i <ed to s tee l shoe , i n t e r n a l gro t p ipe

FIGURE 3.1 : General arrangement of some MV pile types

3

sections) or it may be made from a reinforced precast

concrete column. Hollow steel section mandrels may also

be filled with concrete on completion of driving, or a

bulbous shape may be formed by driving out a concrete

plug with an internal drop hammer.

MV piles may be installed at rakes ranging from vertical

to as little as 2D degrees inclination from the

horizontal. Techniques have also been developed to

install MV piles under water. Shaft friction capacity

of MV piles in a given soil is hign in comparison to,

for example, preformed driven displacement p ;les such as

precast piles or steel joists, and is of a similar order

of magnitude to the shaft capacity of similar sized

driven displacement cast in situ pile types such as

Franki piles. For this reason MV piles are generally

identified as "friction piles'* and consequently their

most frequent application is in deep soft soils including

loose sands, and soft silty and clayey soils. Their low

driving resistance also enables MV piles to be installed

into gravels and dense sands.

Due to the hign snaft friction capacity a frequent

application of MV piles is .in tensile load applications

such as high capacity retaining wall anchors and dry

dock and weir foundations. Transmission line tower

masts and chimnev unions have also been supported

on MV piles, which, in such cases, are usea to provide

4

reaction to both tensile and compressive loads. In

terms of numbers of piles installed the most frequent

use of MV piles has been as anchor piles, particularly

in harbour and canal construction where they have been

used as a cost effective alternative to conventional

tendon type ground anchors. The harbour authorities of

Duisborg, West Germany for example consider MV pile

anchors a preferred anchor technique, and the EAU (1975)

recommend MV piles tor retaining wail support and other

tensile load applications.

3.2 Historical development

The MV piling system was invented and developed by

Dr. -Ing Ludwig Muller in the early 1950s in West

Germany. The Company. Dr. -Ing Ludwig Muller und Sonne

Gesellschaft fur Neuzeitliche Bautechnik K.G. (later to

become Dr. -ing Ludwig Muller und Sohne Gesellscnaft fur

Bautechnik MBH i Co K.G.), was subsequently established

in Marburg an der Lahn, West Germany, to market the MV

piling system under a licensee arrangement, with

Dr. -Ing Muller remaining as patent holder and licensor.

The first licensee of the MV piling system was Dortmund

Hoeder Hiittenunion, a West German sheet pile manufac

turer, in 1955 . The initials "MV" in MV pile are an

abbreviation of the German - M uller Verpress pfahl -,

which roughly translated, means Muller grouted pile.

5

Fundamental to the successful operation of the MV piling

system is the use of a grout with suitable stability,

flow and strengtn properties. Early MV grouts contained

materials such as trass, bentonite and asbestos fibre in

addition to a fluid sand-cement-water mix. Tricosal M V ,

an additive to MV grout which now finds wide acceptance

and success, was subsequently developed specifically for

Muller und Sohne by Chemische Fabrik Gr'unau GmbH, also

of West Germany. The original intention with early MV

piles was that the hardened grout need oe o m y as stiong

as was required to safely transfer the applied axial

load in shear to tne surrounding soil and that the drive

mandrel would be designed to support applied axial and

bending loads.

Grout made with Tricosal M V , however, possesses

sufficient strength for 1 .. to be used to both shed load

to the soil through shaft friction as well as to

function as the main axial load bearing member. The

drive mandrel thus becomes a recoverable item, and its

original function is now usually supplanted by the grout

column, reinforced as required.

To date, over 600 000m of MV piles ranging in length

from 3,0 to rarely more than 30m (typically about 3m)

and with diameter ranging from 0,1m up to 0,9m have been

installed throughout the world, but mostly in West

Germany and bordering European countries. Despite their

6

considerable success in Europe very little appears to be

known about the MV piling system elsewhere. Begcmann

(1965) briefly refers to the MV pile in presenting a

tensile load capacity design approach using the "adhesion

jacket cone". Hammond (1967 pp. 58-61) describes MV

piles as "a driven steel pile in which pressure grouting

is ingeniously employed", and Bazant (1979 p. 363)

simply observes that MV piles are useful in resisting

tensile loads. A number of European publications

aescriue siie conditions and contractz, often with test

load data, in which MV piles were used. Some of these

include, Mtfller (1961, 1965), Kiessling (1960), Forster

(1956), Hecht (1961), Jeske and Haman (1962) and Kdhling

(1962). The "Grundbau Taschenbuch" (1966, p. 621) refers

briefly to MV piles as a general piling technique, while

MV piles are recommended as a preferred anchoring

technique in embankment construction in EAU (1975). MV

pil«'3 had not been incorporated in EAU recommendations

prior to 1975. Their inclusion in the 1975 edition

signifies impo tant recognition of the technique by

construction authorities in West Germany. The Larssen

sheet piling handbook (Larssen-Handbuch [I960])

frequently refers to MV piles, again as an alternative

to conventional ground anchors.

Jelinek (1962) submitted the first proposal for a

general design approach to MV pile bearing capacity and

Jelinek and Ostermayer (1964) discussed the tensile load

capacity of M7 piles.

7

The Larssen-Handbuch (1960) describes the design of MV

piles when used as retaining wall anchors. Their

approach is similar to that of EAU (1975, S. 238 fl).


South African experience with the MV piling technique

has been limited to a single contract of significance,

though a number of small contracts nave been performed.

During 1977 GrinaKer Filed foundations (t'ty) Limited

installed some 1300m of MV piles, rated at working loads

of between 350kN and 1200kN for the Wentworth Hospital

redevelopment. The site is located in the Bluff area of

Durban, Natal, where extensive and deep deposits of

Berea Red Sand occur. Pile lengths ranged from 4m to

9m. The pilinq contract was won in competition to

vibroflotation.

An MV pile field testing programme has also been

initiated by the South African Licensees and the present

laboratory investigation is an extension of this work.

Author Guy John Evelyn

Name of thesis Behaviour Of A Model Mv Pile In Sand Bearing Capacity Implications. 1987

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