Soil Analysis and Structural Design of Piles

29 Pages·2017·1.06 MB·English

“Soil Analysis and Structural Design of Piles”
Submitted in partial fulfilment of the requirements
for the degree of
BACHELOR OF ENGINEERING
(Civil Engineering)

Submitted by

Sayed Abid – 14DCE75
Shaikh Tausif – 14DCE80
Shaikh Jameel – 14DCE78
Ansari Mohammed Hammad – 14DCE67

Under the guidance of

Prof. Dada Patil
Department of Civil Engineering
Anjuman-I-Islam’s Kalsekar Technical Campus
Plot No. 2 3, Sector – 16, Near Thana Naka, Khandagaon,
New Panvel, Navi Mumbai. 410206

Page 1
CERTIFICATE

This is to certify that Mr. Sayed Abid, ShaikhTausif,
Shaikh Jameel, Ansari Mohammed Hammad has
satisfactorily completed and delivered a Project-A seminar
report entitled “Soil Analysis and Structural Design
of Piles” submitted in partial fulfillment of the requirements
for the award of the degree of Bachelor of Engineering in
Civil Engineering course conducted by university of
Mumbai in Anjuman-I-Islam’s Kalsekar Technical
Campus, Navi Mumbai.

.

Prof. Dada Patil
(Project Guide)

Dr. RajendraB.Magar Dr.Abdul Razzak Honnutagi
(H.O.D) (Director)

Page 2
ACKNOWLEDGEMENT

We would like to express our sincere thanks to all those who contributed to successful completion of
this project. In particular, we would like to thanks the following people.

We express our gratitude to our guide Prof .DadaPatil sir.of Civil Engineering Department AIKTC for
his guidance in completing project work. His advice and encouragement during preparation of this
report is sincerely appreciated.

We thankful to all the professor of civil engineering department specially Prof .Dada Patil sir for their
guidance and support to the project work. We would also like to extend our gratitude to the
nonteaching staff of AIKTC.

Sincere thanks are extended to
Perfect geotechnics pvt. For providing soil investigation, material testing.
Bhushansanghvi sir.
Vaishnav sir.

Page 3
TABLE OF CONTENTS

S.No DESCRIPTION PAGE NO.
1 5
ABSTRACT
2 6
INTRODUCTION
3 7
LITERATURE REVIEW
4 8
METHODOLOGY
5 13
ANALYSIS OF SOIL
6 15
LABORATORY TESTS
7 21
STRUCTURAL DESIGN OF PILE
8 28
RESULTS AND DISCUSSIONS
9 29
CONCLUSION

Page 4
ABSTRACT

Pile foundations are often used in the soft soils to support heavy structures such as offshore towers,
nuclear power plants, tall buildings, dams and bridges, There are many situations where these
structure may go under dynamic loading, for example: earthquake forces, wave forces, wind forces,
blasting and unbalanced machine etc. There has been a remarkable increase in the study of pile
foundations in the latest twenty years although piles have been used for hundreds of years

The purpose of this report is to analyse the soil and design the foundation by using static formulae.
From the soil analysis and subsurface exploration, the foundation is recommended for the soil strata.
Pile foundation consists of piles that are dug into soil till a layer of stable soil is reached. Pile
foundations transfer building load to the bearing ground with the greater bearing capacity. Pile
foundations are useful in regions with unstable upper soil that may erode or for large structures, pile
foundations are often required to resist lateral loading. Lateral loads come from variety of sources
including wind, earthquakes waves and ship impacts. The lateral capacity of pile is usually much
smaller than the axial capacity and as a result, group of piles are often installed to increase lateral
capacity of the entire foundation system. When vertical or plumb pile groups do not provide sufficient
lateral resistance, the pies can be battered in order to mobilise some of the higher axial capacity to
resist the lateral load.
Piles are relatively long slender members that transmit foundation loads through soil strata of low
bearing capacity to deeper soil or rock strata having high bearing capacity. Piles are also used to
anchor structures against uplift forces and to assist structures in resisting lateral and overturning
forces

In this project work, a proposed residential building (G + 16) at Indu Ganesh Cooperative Housing
Society, Chunabhatti, Mumbai, is taken up for the foundation design. The tests on soil & rock are
carried out by taking the help of Geocon International Pvt. Ltd. The pile cage is designed with the
manual calculations & the pile caps covering a group of 2, 3 ,4 & 5 piles are designed using the Excel
sheets. This is done below the typical columns C1 & C2. The work aims at the soil investigation &
the structural design of the pile groups & pile caps, incorporating the superstructure loads as inputs.
The static equations are used for the calculations.

Page 5
Chapter 1
INTRODUCTION

Piles are deep foundations used when the bearing capacity of shallow foundation is not enough to
ensure the support of the superstructure. Superstructure results in vertical force, due to its weight as
well as additional loads, which are axially transferred to the pile and, through its shaft and base, to the
soil, possibly reaching a stiffer layer.

The analysis of the load transfer mechanism in single pile under axial loading is therefore an essential
basis of deep foundation design. It is very important that the physical interaction between pile and soil
is carefully studied the settlement analysis is also fundamental, for the maximum allowable settlement
of a foundation is often most important criteria in its design. Thus, it should be estimated accurately.

The behaviour of single pile under axial loading as far as load distribution and settlement along the
pile are concerned, have been analysed through numerous methods.

Pile can be driven or cast in place. Pile driving is achieved by impact dynamic force from hydraulic
and diesel hammer vibration or jacking. Concrete and steel piles are most common. Driven piles
which tend to displace a large amount of soil due to driving forces are called full displacement piles.
Cast in situ (or bored) piles do not cause any soil displacement therefore, they are non displacement
piles.

Pile may be loaded axially or transversely. The limit state methods necessary to be considered in the
design of piles are as follow
1] Bearing resistance failure of the pile foundation
2] Insufficient compression resistance of the pile
3] Uplift or insufficient tensile resistance of the pile
4] Failure in the ground due to the transverse loading
5] Excessive settlement, heave or lateral movement
6] Loss of overall stability
7] Unacceptable vibration

Deep foundation is much more expensive than a shallow foundation. It should be adopted only when a
shallow foundation is not feasible. In certain situations, a fully compensated floating raft may be more
economical then deep foundation. In some cases, the soil is improved by various methods to make it
suitable for shallow foundation.

Page 6
Chapter 2

LITERATURE REVIEW

Deep foundations are employed principally when weak or otherwise unsuitable soil exists near the
ground surface and vertical loads must be carried to strong soils at depth. Deep foundations have a
number of other uses, such as to resist scour; to sustain axial loading by side resistance in strata of
granular soil competent clay; to allow above-water construction when piles are driven through the
legs of a template to support an offshore platform; to serve as breasting and mooring dolphins; to
improve the stability of slopes; and for a number of other special purposes. The principal deep
foundations are driven piles and drilled shafts. (Reese, Limon C., 2006)
Piles are structures of timber concrete, and/or steel, used to transmit surface loads to lower levels in
the soil mass. This may be by vertical distribution of the load along the pile shaft or a direct
application of load to a lower stratum through the pile point. A vertical distribution of the load is
made using a friction, or “floating” pile and a direct load application is made by a point, or “end
bearing”, pile. This distinction of piles is purely one of conveniences since all piles function as a
combination of side resistance and point bearing except when the pile penetrates an extremely soft
soil to a solid base.
2.1. Related Research
Rodrigo Salgado and Johan Lee (1999) in their research titled Pile Design Based on Cone
Penetration Test Results had an inspirational summary. They said that since the CPT methods
available for pile design were developed under different conditions, the selection of the method
should take into account the differences and recommendation of the methods.
Static cone penetration is better related to the pile loading process than the SPT. The test is performed
quasi-statically and resembles a scaled-down pile load test. In the present study, in order to take
advantage of the CPT for pile design load settlement curves of axially loaded single piles bearing in
sand were developed in terms of normalized base resistance (b /q ) versus relative settlement (s/B).
e c
For more general use of CPT-based pile design method, a correlation between SPT blow count N
and the cone resistance QC can be used. Field SPT and CPT test data for an Evansville sandy soil
site suggests the correlation between QC and N proposed by Robertson and Campanula (1983) is
likely applicable to Indiana sandy deposits.
Other research had been done also by Murad Y. Abu-Farsakh and Hani H. Titi (2004) titled
Assessment of Direct Cone Penetration Test Methods for predicting the Ultimate Capacity if
Friction Driven Piles. Their study presented an assessment of eight direct CPT methods to estimate
the ultimate load capacity of square PPC friction piles driven into Louisiana soils. Analysis was
conducted on 35 friction piles loaded to failure with CPT’s conducted adjacent to each test pile.
The measured ultimate load capacity for each pile was determined from the load settlement curve
using the Butler-Hoy method (1977) ultimate
Load capacity of each pile was also determined using the CPT methods, and the static α and β
methods.
Their study showed that the ultimate pile capacity can be determined using the CPT data with the
acceptable accuracy. The performance of the CPT methods may vary according to the performance
used to determine the ultimate pile load cap of the soil at the site. The conclusions of this study are
based on the ultimate pile capacity interpreted from the load test using the Butler-Hoy method
(1975)

Page 7
Chapter 3
METHODOLOGY
There are various methods of determining the load carrying capacity of single piles. They are:
o By Static Bearing Capacity Equations
o Based on SPT Results
o Based on CPT Results
o By Pile Loading Tests
3.1 Static Bearing Capacity Equations
The static methods give the ultimate bearing capacity of an individual pile, depending upon
the characteristics of soil.
Assume a pile of diameter D is driven to a length L from the ground surface as shown in
Fig.1. Let Q be the net load applied at the head of the pile. The weight of pile is W and unit
u
weight of soil is Y. If q and q are the unit base and skin friction respectively, then we can
b s
write the ultimate capacity of pile as:
Q + W – γD = q A + qA ———- (1)
u f b b s s

FIG. 1: VERTICAL LOAD ON A SINGLE PILE

Page 8
If the weight of the pile and weight of the displaced soil are assumed as nearly equal we have:
Q = q A + qA
u b b s s

Q + W – γD = q A + qA ———- (1)
u f b b s s
If the weight of the pile and weight of the displaced soil are assumed as nearly equal we have Q =
u
q A + qA
b b s s
Then, q = ½ B N + σ N + s N – σ
b γ γ v q u c v
Or, q = ½ B N + σ (N -1) + s N ———- (2)
b γ γ v q u c
Similarly unit skin friction can be obtained as :
q = s + Kσ tanδ ———- (3)
s a v
Where, σ is the effective normal stress acting alone the shaft of the pile and the variation of the
v
normal stress is linear. s is the adhesion between, pile and surrounding soil. The average effective
a
normal stress is (0+σ )/2 = σ /2 = σ’
v v v
Hence,
q = s + K σ’ tanδ ———- (4)
s a v
Therefore, the net ultimate pile capacity becomes:
Q = [ ½ BγN + σ (N – 1) + s N ]A + [s + K σ’ tanδ]A ———- (5)
u γ v q u c b a v s
This is the general equation applicable to soil having both cohesion and friction.
Cohesionless soil – If soil is cohesionless, cohesion is zero and the Eq.(5) reduces to:
Q = σ (N – 1)A + K σ’ tanδA ———- (6)
u v q b v s
The Eq(6) neglects the term ½ BγN , since pile width is very small as compared to its length. The
γ
value of N is obtained by the relationship suggested by Berezantsev (1961), which is shown in Fig..
q
To use the graph shown in Fig.2 the value of ɸ should be known and this can be obtained from the
results of Standard Penetration Test using the graph given in Fig.2. The suggested relation can only be
used when piles are driven to depths greater than five times the pile width if less use Terzaghi’s
bearing capacity equation. The term N is very sensitive to ɸ a relative small error in estimating ɸ
q
will lead to much larger error in N .
q
Meyerhof has suggested that the bearing capacity of piles driven into loose sands can be doubled
owing to compaction. The suggested value of K with δ is given in Table 1 below.

Page 9
Table 3.1
Values of K and δ
Pile material δ K
Loose Dense
Steel 20 0.5 1
Concrete 0.75 ɸ 1 2
Wood 0.67 ɸ 1.5 3

Cohesive soil– In cohesive soil, the angle of internal friction is zero. Hence, the above Eq.(5) can be
written as:
Q = s N A +s A ———- (7)
u u c b a s
In the above equation s is the adhesion between pile and surrounding soil. S is the undrained
s u
shear strength at base. Driving piles in clay reduces shear strength in many ways. If the
reduction factor is α, then we can write:
α = s /s’ ———- (8)
a u

Page 10