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Transcript of Mini Project
ACKNOWLEDGEMENT
We express our sincere thanks to some without their assistance this work could not be undertaken at all. We convey our deep sense of gratitude to
For providing us the opportunity to take up this project.
We own the most diverse and deepest gratitude to our guides who have spent their valuable time and effort to help us to give information about the project.
We are thankful to Sri.B.G.M.K.Chari, DGM (Civil)/S.M.S (Construction) for his esteemed guidance throughout the project. We extend our sincere thanks to Mr.V.S.N.Raju, Asst. Manager (Civil)/S.M.S (Construction) for giving us technical insight about the project aspects in particular. We are also thankful to Mr.V.Ravi Kumar, M.N.Dastur & Co. for his valuable guidance and acquaintance of various civil structures at site.
Lastly we are also thankful to Mr.J.Prabhakar Rao, Asst. Manager (T&DC), VSP for posting us at SMS construction zone for the study.
TABLE OF CONTENTS
SL. NO. TITLE PAGE
1. INTRODUCTION 4
2. STEEL PLANT OVERVIEW 7
3. REVIEW OF LITERATURE 13
4. CONSTRUCTION OF BORED CAST-IN-SITU PILES
Specification for bored RCC piles 25
Piling work 27
Workmanship 30
Construction of Pile 32
Properties of Bentonite 39
Pile load tests 42
5. CONCLUSION 54
6. BIBLOGRAPHY 56
1 | P a g e
ABSTRACT
Technology developments in the field of construction has put more challenges to the
infrastructure to sustain the severe development of industries and of large scale building of
highways, bridges, tunnels & dams.
Apart from this Civil Engineering have many diverse and important encounters with soil. It
is particularly helpful in the design of foundations, rigid and flexible pavements,
underground and earth retaining structures, embankments and excavations.
The loads from any structures have to be ultimately transmitted to soil through the
foundation of the structure. Thus the foundation is an important part of a structure, the type
and details of which can only be decided upon with the knowledge and application of the
principles of soil mechanics.
Knowledge of soil mechanics is a prerequisite to be a successful foundation engineer.
In the present study entitled “Construction of Bored cast-in-situ piles”, we study about the
various aspects related to the construction procedures of bored pile foundations that are
constructed at VISAKHAPATNAM STEELPLANT, materials used in the construction of
piles and various load tests.
2 | P a g e
INTRODUCTION
3 | P a g e
INTRODUCTION
Civil engineers may construct many types of structures to serve various infrastructural
requirements and these include infrastructural buildings, dams, bridges, roads, railway
lines and related structures, ports etc.
All these structures are designed to transmit load to the soil on which they rest. To enable
the stress to be safely transferred to the soil, these structures are soil linked and called
foundation. The size and shape of the foundation determines the stress that is finally
transferred to the soil underneath. Once the size and shape are determined, the substructure
or the foundation is to be structurally designed to withstand the load of the superstructure
on one side and the reaction from the soil from the outer side.
A foundation should be designed such that the soil below doesn’t fail in shear. The
settlement which the soil can safely withstand is known as allowable bearing pressure.
There are generally two types of foundations:
1. Shallow foundations
2. Deep foundations
1. SHALLOW FOUNDATIONS:
Shallow foundations are the most common type of foundations and can be laid using
open earth excavation by allowing natural slopes on all sides. These are also called
“Open foundations”. These types of foundations are for depths of 2 to 3 meters and
4 | P a g e
are normally convenient foundations, provided for structures of moderate height
built on soils having satisfactory amount of bearing capacity.
2. DEEP FOUNDATIONS:
When the foundations have to carry heavy structural loads through a weak
compressible soil, the foundations are called “Deep foundations”. These are of two
types:
Pile foundations
Well foundations
PILE FOUNDATIONS:
A pile may be defined as a long vertical load transferring elements composed of timber,
steel, concrete or combination of them.
Piles are used to carry vertical loads through weak soil to dense strata having high bearing
capacity. In normal ground conditions, they can resist large uplift and horizontal loads,
hence, can be used as foundations of multistoried buildings, transmission line towers,
retaining walls, bridge abutments.
Pile foundations are adopted in the following situations:
Low Bearing Capacity of soil .
Non availability of proper bearing stratum at shallow depths.
5 | P a g e
Heavy loads from the super structure for which shallow foundation may not be
economical or feasible.
When the plan of structure is irregular relative to its outline and distribution
It would cause non uniform settlement if a shallow foundation is constructed. A pile
foundation is required to reduce differential settlement.
Pile foundations are required for the transmission of structural loads through deep
water to a firm stratum.
Pile foundations are used to resist horizontal forces in addition to support the vertical
loads in earth retaining structures and tall structures that are subjected to horizontal
forces due to wind and earthquake.
Piles are required when the soil conditions are such that a washout, erosion or scour
of soil may occur from underneath a shallow foundation.
Piles are used for foundations of some structures such as transmission towers, off-
shore platforms which are subjected to uplift.
In case of expansive soils such as black cotton soils, which swell or shrink as water
content changes, piles are used to transfer the below the active zone.
6 | P a g e
STEEL PLANT
OVERVIEW
7 | P a g e
VISAKHAPATNAM STEEL PLANT OVERVIEW
Visakhapatnam steel plant is one of the prestigious steel plants in India which is located at
Visakhapatnam of Andhra Pradesh.
VSP is only shore based steel plant in India. It is of 3 million metric tons capacity per
annum with sophisticated technology. It is only steel plant to get all ISO certificates like
ISO 9001, ISO 14001, ISO18001 and 5s certificates for 53 departments ERM [Enterprise
Risk Management] and ERP [Enterprise Resource Planning] are also in implementation
stage. It won Prime Minister Trophy for 2 times. Visakhapatnam steel plant is also called
"Jewel of Andhra Pradesh”. Foundation stone was laid by late Prime Minister Smt. Indira
Gandhi.
1. Visakhapatnam steel plant, the first coastal based steel plant of india is located 16km
south west of city of destiny, i.e. Visakhapatnam. The site is situated south of
National Highway no.5 and the east coast Railway line between Visakhapatnam and
Chennai sea level (MSL). The plant site located at latitude of 17°37’N and longitude
of 83°12J E.
2. CLIMATE OF VISAKHAPATNAM:-
The climatological dates on vicinity of the site are as follows:
RAINFALL:-
Highest monthly : 606 mm
Highest daily : 370 mm8 | P a g e
Highest recorded temp : 40.50 C
Lowest recorded temp : 16.50 C
Relative humidity : 4%(min) to 100% (max)
Wind velocity : 32.5 kmph (highest monthly wind speed fir 24hr)
3. EARTHQUAKE FACTOR:-
This plant is falling under Zone II as per IS: 1893.
4. RAILWAYS:-
The nearest railway station is Duvvada on the Visakhapatnam Chennai line about
10km from the plant and the Visakhapatnam railway station is about 30km from the
plant.
5. ROADS:-
The national highway passes beside the plant.
6. SEAPORT:-
The nearest seaport at Visakhapatnam is about 16 km from the plant site. A new port
at Gangavaram is under development and it is adjacent to the north east boundary
me the plant.
9 | P a g e
7. AIRPORT:-
The nearest airport at Visakhapatnam is about 12 km from the plant.
8. COMUNICATION:-
Postal and other telecommunication facilities are well established in Visakhapatnam.
VSP by successfully installing & operating efficiently Rs.460 crores worth of
pollution control & environmental control equipment and converting the barren
landscape by planting 3 million plants has made the steel plant , steel township and
surrounding areas into a heaven of lush greenery.
VSP exports quality pig iron & steel products to Sri Lanka, Myanmar, Nepal,
Middle East, USA& south East Asia. RINL-VSP was awarded “Star trading house”
status during 1997-2000 having established a fairly dependable export market.
Having a total manpower of 17000, VSP has envisaged a labour productivity of
not less than 230 per man year of liquid steel which is the best in the country and
comparable with international levels.
Steel is one of the most important components that can strengthen the economic
backbone of any country.
EXPANSION PROJECT
Introduction:-
1. Visakhapatnam steel plant (VSP) is an integrated public sector steel plant owned by
Rashtriya Ispat Nigam limited(RINL), built an annual production capacity of about 3
million tons of liquid steel per year with provisions for future expansion.10 | P a g e
2. The detailed project report was prepared by the principal consultant, M.N.Dastur
&Co.(P)Ltd in 1980. The project has envisaged iron making capacity of 3.4mtpy,
2.66mtpy including 0.246mtpy of saleable billets. The iron and steel making
facilities were generally based on the utilization of soviet equipment, while rolling
mills were from other sources.
3. VSP has been able to achieve hot metal production of about 4mtpy from its two blast
furnaces for the last two years. Steel melt shop has also been able to produce about
3.5 million tons of liquid steel, 3.17mtpy of saleable steel, out of which for sale
constituted about 0.18 million tons in 2003-04.
4. Keeping in view the upturn in global and domestic steel demand, VSP is envisaging
increasing their plant capacity to about 605 mtpy of hot metal initially, followed by
commensurate increase in production of liquid and saleable steel. Future plan
envisages increase in plant capacity to about 10mtpy.
Construction volume:-
5. The quantum of major construction work involve in 6.5mtpy stage is given in table:
QUANTITIES OF CONSTRUCTION WORK
Item of work Unit Quantity
Piling 600mm dia 120 ton capacity nos 26,100
Concreting of all grades cum 700,000
Structural steel work ton 185,00011 | P a g e
Equipment erection ton 102,000
Pollution control and environmental protection:-
6. Adequate pollution control and environmental protection measures have been
considered for this plant arising out of the expansion plans. Due consideration has
been given to water, environmental protection, work-zone pollution control, solid
by-products management, plant safety, greenbelt & landscaping environmental
monitoring.
Conclusion:-
7. From the financial results projected above, it can be concluded that the project is
very attractive and will place RINL in the topmost bracket of earning potentiality.
12 | P a g e
REVIEW OF
LITERATURE
13 | P a g e
REVIEW OF LITERATURE
Terminology:
Raker Pile: - The pile which is installed at an angle to the vertical.
Bearing Pile: - A pile formed in the ground for transmitting the load of structure to the soil
by the resistance developed at its tip and/or along its surface. It may be formed either
vertical or at an inclination (Batter Pile) and may be required to take uplift. If the pile
supports the load primarily by resistance developed at the pile point or base it is referred to
as ‘End Bearing Pile’; if primarily by friction along its surface, then as ‘Friction Pile’.
Bored Cast-in-situ Pile:-The pile formed within the ground by excavating, with or
without the use of a temporary casing and subsequently filling it with plain or reinforced
concrete. When the casing is left permanently it is termed as “cased pile” and when the
casing is taken out it is termed as “uncased pile”.
In installing a bored pile the sides of the borehole (when it does not stand by itself)
is required to be stabilized with the aid of a temporary casing, or with the aid of drilling
mud of suitable consistency. For marine situations such piles are formed with permanent
casing (liner).
Cut-Off Level: - It is the level where the installed pile is cut-off to support the pile caps or
beams or any other structural components at that level.
14 | P a g e
Working Pile: - A pile forming part of foundation of a structural system.
Net Displacement:-The net movement of the pile top after the pile has been subjected to a
test load and subsequently released.
Test Pile:-A pile which is selected for load testing and which is subsequently loaded for
that purpose. The test pile may form working pile itself, if subjected to routine load test
with loads up to one and one half times the safe load.
Trial Pile:-Initially one or more piles, which are not working piles, may be installed to
assess load carrying capacity of a pile. Pile of this category is tested either to its ultimate
load capacity or to twice the estimated safe load.
Total Elastic Displacement:-This is the magnitude of the displacement of the pile due to
rebound caused at the top after removal of a given test load. This comprises two
components:
a) Elastic displacement of the soil participating in the load transfer.
b) Elastic displacement of the pile shaft.
Total Displacement (Gross):- The total movement of the pile top under a given load.
Ultimate Load Capacity: - The maximum load which a pile can carry before failure of
ground (when the soil fails by shear).
Datum Bar: - A rigid bar placed on immovable supports.
Kentledge: - Dead-weight used for applying a test load on piles.
15 | P a g e
Routine Test: It is carried out on a working pile with a view to check whether pile is
capable of taking the working load assigned to it.
PILE FOUNDATION:
Piles find application in foundation to transfer loads from a structure to competent
subsurface strata having adequate load bearing capacity. The load transfer mechanism from
a pile to the surrounding ground is complicated and could not yet be fully ascertained,
although application of piled foundations is in practice over many decades.
Broadly, piles transfer axial loads either substantially by skin friction along its shaft
or substantially by the end bearing. Piles are used where either of the above load transfer
mechanism is possible depending upon the subsoil stratification at a particular site.
Construction of pile foundations require a careful choice of piling system depending upon
the subsoil conditions, the load characteristics of a structure and the limitations of total
settlement, differential settlement and any other special requirement of a project.
16 | P a g e
Piles are classified into many types depending on the materials used, the mode of transfer
of load, the method of construction, the use, displacement of soil, sectional area and size as
described below.
Classification based on materials used:
Steel piles
Concrete piles
Timber piles
Composite piles
Classification based on use:
Load bearing piles
Compaction piles
17 | P a g e
Tension piles
Sheet piles
Fender piles
Anchor piles
Classification based on Load Transfer Mechanism:
End-bearing piles
Friction or floating piles
Combined end-bearing and friction piles
Classification based on displacement of soil:
Displacement piles
Non-displacement piles
Classification based on Method of Installation:
Driven precast piles
Driven cast-in-situ piles
Bored precast piles
Bored cast-in-situ piles
18 | P a g e
Classification based on sectional area:
Circular
Square
Octagonal
H
Tubular
Classification based on size:
Micro piles dia < 150mm
Small dia pile dia 150 to 600mm
Large dia pile dia > 600mm
Classification based on Inclination:
Vertical Piles
Inclined or Raker Piles
Loads coming on pile foundation:
All the loads from super structure viz. Dead loads, Live loads Wind loads and
Seismic loads.
The loads from the surrounding soil in case of seismic event.
Water loads in the case of off-shore structures.
Load carrying mechanism of piles:19 | P a g e
End bearing cum friction piles carry vertical compressive loads partly by means of
resistance offered by the hard stratum at the tip of the pile and partly by the friction
developed between the pile shaft and soil.
Pure friction piles carry the major part of loads only by means of friction developed
between pile shaft and soil; and pure End bearing piles only by means of bearing
resistance at the tip of the pile.
In both the above cases lateral loads are carried by the lateral resistance offered by the
surrounding soil.
BORED PILE:
Bored pile is a type of reinforced concrete pile, which is used to support high building
producing heavy vertical loads.
Bored pile is a cast-in-place concrete pile where the bored piles have to be cast on the
construction site, while other concrete piles like Spun Pile and Reinforced Concrete Square
Pile are precast concrete piles.
Bored piling is cast by using bored piling machine which has specially designed
drilling tools, buckets and grabs, it’s used to remove the soil and rock. Normally, it can be
drilling into 50 meters depth of soil. The advantage of bored piling is its drilling method, little
vibration and lower noise level.
The drilling method depends on the condition of soil, piling contractor has to do soil
investigation and decide which drilling technology has to be carried on. Piling contractor
decides the correct drilling technology and minimize disturbance of the surrounding soil. For
20 | P a g e
cohesion-less soils such as sands, gravels, silts, etc., whether it’s under the water table or not,
the pile bore hole must be supported using steel casing or stabilizing mud such as bentonite
suspension.
Rotary boring techniques offer larger diameter piles than any other piling method
and permit pile construction through particularly dense or hard strata. Construction
methods depend on the geology of the site. In particular, whether boring is to be
undertaken in 'dry' ground conditions or through water-logged but stable strata i.e. 'wet
boring'.
For end-bearing piles, drilling continues until the borehole has extended a sufficient
depth (socketing) into a sufficiently strong layer. Depending on site geology, this can be a
rock layer, or hardpan, or other dense, strong layers. Typical socket depths are equal to the
diameter of the pile in hard rock layers and 2.5 times the diameter of the pile in soft rock
layers.
'Dry' boring methods employ the use of a temporary casing to seal the pile bore
through water-bearing or unstable strata overlying suitable stable material. Upon reaching
the design depth, a reinforcing cage is introduced; concrete is poured in the borehole and
brought up to the required level. The casing can be withdrawn or left in situ.
'Wet' boring also employs a temporary casing through unstable ground and is used
when the pile bore cannot be sealed against water ingress. Boring is then undertaken using
a digging bucket to drill through the underlying soils to design depth. The reinforcing cage
is lowered into the bore and concrete is placed by tremie pipe, following which, extraction
of the temporary casing takes place.
21 | P a g e
A common mode of failure for drilled piles is formation of a reduced section due to
the collapse of the walls of the shaft during installation, reducing the pile capacity below
applied loads. Drilled piles can be tested using a variety of methods to verify the pile
integrity during installation.
Advantage of bored piles:
Length can readily be varied to suit variation in level of bearing stratum.
Soil or rock removed during boring can be inspected for comparison with site
investigation data.
In-situ loading tested can be made for large diameter pile bore holes.
Very large bases can be formed in favorable ground.
Drilling tools can break up boulders or other obstructions which cannot be penetrated
by any form of displacement piles.
Material forming pile is not governed by handling or driving stresses.
Can be installed in very long lengths without appreciable noise or vibration and no
ground heave.
Can be installed in conditions of low headroom.
22 | P a g e
Disadvantages:
Concrete in shaft is liable to squeezing or necking in soft soils where conventional
types are used.
Special techniques are needed for concreting in water bearing soils.
Concrete cannot be inspected after installation.
Enlarged base cannot be formed in cohesion less soils.
Cannot be extended above ground level without special adaption.
23 | P a g e
CONSTRUCTION OF
BORED
CAST-IN-SITU
PILES
24 | P a g e
SPECIFICATION FOR BORED CAST-IN-SITU REINFORCED
CEMENT CONCRETE PILES
GENERAL:
Surveyed by total station survey instrument.
Survey checked by traverse method.
Soil and site condition.
Soil strata are varying. Here it is mainly metallurgical waste. The soil is up to 7 to 9m.
The local site and traffic condition is good. Site is connected to road which is from the
way of rolling mills and other through project plaza gate.
BORED CAST-IN-SITU REINFORCED CEMENT CONCRETE PILES:
SCOPE OF WORK:
The work covered under this specification includes provision and installation of
bored cast-in-situ reinforced concrete piles of different to competent rock strata.
Routine load test on piles, pile integrity test are specified.
And equipment collection of soil samples of various strata and founding rock layer,
measurements of final depth and bored diameter etc., complete as specified.
25 | P a g e
The piles shall be cast with grade of concrete and reinforcement as specified and by
suitable method approved by consultant and samples of concrete shall be taken for
testing in an approved laboratory.
The scope of pile testing shall include excavation to required depth and size,
placement of kentledge, reaction loading, reaction blocks or frames for vertical
compression, pill-out and lateral load tests, preparation of pile heads by breaking and
chipping up to specified test level and making good the same for load testing and
conducting routine load test of working piles.
Integrity test shall be carried out on a number of selected piles to detect any defects
like cracks, intrusion and diameter changes etc., if any on pile shaft.
EQUIPMENT AND ACCESSORIES:
The equipment and accessories would depend upon the type of bored
cast-in-situ piles chosen in a job and would be selected giving due consideration to the
subsoil strata, ground water conditions, type of founding material and the required
penetration therein wherever applicable. Among the commonly used plants, tools and
accessories, there exist a large variety, suitability of which depends on the subsoil
conditions and manner of operations, etc.
Boring operations are generally done by rotary or percussion type drilling rigs using
direct mud circulation or reverse mud circulation methods to bring the cuttings out.
26 | P a g e
In soft clays and loose sands bailer and chisel method, if used, should be used with
caution to avoid the effect of suction. Rope operated grabbing tool or Kelly mounted
hydraulically operated grab are also used. The grab method of advancing the hole avoids
suction. The size of the cutting tool should not be less than the diameter of the pile by more
than 75 mm.
PILING WORK:
1. General:
Piles shall be bored cast-in-situ reinforced concrete type with safe load bearing
capacities as stated below:
Pile diameter (mm) Capacity (tons)
400 55
600 120
1000 300
Cement:
For piling work, Blast Furnace Slag Cement shall be used. Ordinary Portland
cement of 43 grade shall be used with prior approval from consultant; if there is any doubt
in the quality of cement, sample for testing are sent to employer’s testing laboratory.
Cement shall be stored on raised platforms inside stores covered on all sides and roof with
provision for ample ventilation. Different types of cements shall be stored separately and
more than 10 bags of cement shall not be stacked one above the other in the stack. It is so
arranged that the bags from the oldest consignment in the stack can conveniently be
removed first for use on first in first out (FIFO) basis. Cement which is hardened, clodded
or deteriorated due to over stacking or long storage shall not be used in works and shall be
removed from site immediately.
27 | P a g e
Aggregates:
All aggregates shall confirm to IS: 383. Coarse aggregates shall be approved
crushed stone or gravel washed clean. Fine aggregates shall be river or pit sand. Coarse and
fine aggregates shall be stored at site separately on clean and hard base or in separate
compartments or hoppers. Samples of aggregates to be used shall be submitted to the
consultant for approval before commencement of work. No aggregate shall be used without
prior approval of the consultant. If necessary, grading of aggregates shall be maintained by
blending different sizes of aggregates that shall be brought to site and stacked in separate
stock piles. Sampling of aggregates shall confirm to IS: 2430 and tests shall confirm to IS:
2386. The percentage of flaky and elongated pieces should not exceed 15%.
Reinforcement:
MS round bars shall confirm to grade I of IS: 432- mild steel and medium tensile
steel bars and deformed bars shall confirm to IS: 1786- high strength deformed steel bars
(Fe 415). All reinforcements shall be free from oil, paint, loose rust, mill scale or other
matters likely to weaken or destroy their bond with concrete.
Binding wire:
Binding wire shall be approved 20 SWG annealed iron wire.
Water:
Water shall be clean and potable quality of pH value ranging between 6 to 8.
Bentonite:
Bentonite shall confirm to appendix A of IS: 2911(Part-1/Section-2).
28 | P a g e
2. CONCRETE MIX:
The concrete shall be controlled concrete as defined by IS: 456 and IS: 2911(Part-
1/Section-2). The grades of concrete shall be specified and the strength requirements shall
be in accordance with IS: 456.
Aggregates in each mix of concrete shall be graded and the water cement ratio
controlled in accordance with IS: 456 and frequent tests are conducted to ensure the usage
of correct grade of concrete.
3. MIXING:
All components of concrete shall be proportioned by weight for each grade. Mixing
shall be done in a concrete batching plant.
Consistency: Consistency of concrete for cast-in-situ piles shall be suitable to the
method of installation of piles. Concrete shall be so designed or chosen as to have
homogeneous mix having a flow able character consistent with the method of
concreting under the given conditions of pile installation. In achieving these results,
minor deviations in the mix proportions used in structural concrete may be
necessary.
Tests: Sampling, mixing, curing and testing of concrete specimens shall comply
with IS: 456, 516 and 1199.
4. CONCRETE:
Materials and methods of manufacture for cement concrete shall in general be in
accordance with the method of concreting under the conditions of pile installation.
29 | P a g e
For pile of smaller diameter and depth of up to 10 m, the minimum cement content
should be 350 kg/m3 of concrete. For piles of large diameter or deeper piles, the minimum
cement content should be 400 kg/m3 of concrete.
For design purposes, the strength of concrete mix using the quantities of cement
mentioned above may be taken equivalent to M 15 and M 20.
Where concrete of higher strength is needed, richer concrete mix with greater
cement content may be designed. In case of piles subsequently exposed to free water or in
case of piles where concreting is done under water or drilling mud using methods other
than the tremie, 10% extra cement over that required for the design grade of concrete at the
specified slump shall be used subject to a minimum quantity of cement specified.
Slump of concrete shall range between 150 to 180 mm where concrete is to be
placed under drilling mud by tremie.
Plasticizers or retarders of approved makers may be necessary for ease of concreting
shall be provided.
WORKMANSHIP:
Control of Pile Installation:
Bored cast-in-situ reinforced concrete piles shall be capable of being tested for load
carrying capacity after 28 days of casting. Bored cast-in-situ piles shall be constructed by
suitable choice of installation techniques i.e., use of casing and/or use of drilling mud;
manner of concreting i.e., direct pouring and placing or by use of tremie, choice of boring
tools in order to permit satisfactory installation of a pile at a given site. Sufficient detailed
information about the subsoil conditions is essential to predetermine the details of the
installation technique.
30 | P a g e
Control of Pile Alignment:
Piles shall be installed as accurately as possible as per the designs and drawings
either vertically or to the specified batter. Greater care should be exercised in respect of
installation of single pile or piles in two pile groups.
Displacement - shall not exceed 75mm in any direction from its
true position as approved on drawing.
Verticality - shall not deviate more than 1.5% for vertical piles shall not
deviate more than 4% for raker piles.
In the case of a single pile in a column positional tolerance should not be more than
50 mm (100 mm in case of piles having diameter more than 600 mm). Greater tolerance
may be prescribed for piles driven over water and for raking piles.
Any piles deviating beyond limits and to such an extent that the resulting
eccentricity cannot be taken care of by a redesign of the pile cap of pile ties, the piles
should be replaced or supplemented by one or more additional piles.
31 | P a g e
Construction of Pile:
Rotary Piling Rigs:
The pile boring rigs shall be crawler mounted, hydraulically or mechanically
operated rotary rig with capability for accessories attachments i.e., compressed air
pulveriser, oscillating type liner, different cutting tools etc., or equivalent capable of
drilling or boring through hard compact slag, soft or weathered as well as sound rock with
necessary mud circulation technique. These rigs shall preferably be light, easy to transport
and fully self-erecting so that they can be set up quickly without the aid of auxiliary cranes.
The rigs shall consist of telescopic leaders or Kelly bars expandable tracks and a low
32 | P a g e
Centre of Gravity. The engines generate enough torque (5 to 25 t-m) to bore through hard
compacted slag and sound hard rock at high speed.
Adequate hydraulic steam adaptable to different equipment like hammers, rotary
heads, augers, vibratory heads etc., shall be an essential feature of such rigs.
Tripod Rigs:
Conventional tripod rigs with bailer-chisel arrangement with provision of installing
casings up to depths as necessary based on site condition and equipped with Direct Mud
Circulation (DMC) arrangements shall be deployed.
Boring:
In general, piles bores shall be kept cased with lead-in-tube to prevent ingress of soil
followed by temporary casing to required depth. Minimum length of temporary casing
during boring, if required, using conventional tripod rig, shall be 1.5m. However, actual
length of casing in all cases will depend upon the requirements based on site condition. In
the present site boring was done up to 14 m and casing was inserted up to 6m maintaining
the centre by reference points and also maintaining the level. Inflow of ground water and
soil shall be controlled and sides of bore holes stabilized by using sufficient head of
drilling mud such as bentonite suspension. The head of bentonite slurry shall be kept at
least one metre (1m) above the standing water level.
Pile dia. Minimum depth of Stock length into
(mm) into compact hard rock(mm)
400 800 (2d)
600 1200 (2d)
33 | P a g e
1000 2000 (2d)
Final depth of boring shall be determined by sounding and in case of uncased bores,
diameter of bore at different depths shall be determined by a pantograph or other suitable
means. After completion of boring the bore hole shall be cleaned by controlled air-lift
method of finishing with fresh drilling fluid.
Lowering of reinforcement cage:
On satisfactory completion of boring, the reinforcement cage shall be lowered inside
the bore hole with sufficient numbers of round cement concrete cover blocks attached to
the lateral links. The lap length and the spiral shall be tack welded to the main
reinforcement. The reinforcement cage should go down into the bore hole and in no case
the cage shall be allowed to withstand on its own from bottom of bore to avoid buckling.
Precaution shall be taken to ensure that the cover blocks do not get damaged during cage
lowering.
The minimum clear cover to all main reinforcement in pile shaft shall be not less than
40mm. The minimum clear distance between two adjacent main reinforcement bars should
normally be 100 mm for the full depth of the cage or spirals.
The laterals of a reinforcing cage may be in the form of links
The diameter and spacing of the same is chosen to impart adequate rigidity of the
reinforcing cage during its handling and installation.
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Concreting:
Concreting operations shall not be taken up when the specific gravity of the bottom
slurry is more than 1.12. Concreting shall be done by tremie method in all such cases. The
slurry shall be maintained at least 1.5m above the ground water level if casing is not used.
The temporary casing may not be required except near the top when concreting
under drilling mud. The hopper and tremie should be a closed system embedded in the
placed concrete, through which water cannot pass. The tremie should be large enough with
due regard to the size of the aggregate.
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Bottom of the bore hole shall be cleaned of all accumulated sand, muck and loose
materials by controlled air-lift flushing with fresh drilling fluid. The tremie pipes shall
extend to the bottom of bore hole at start and shall be joined in sections and fitted with the
hopper for receiving concrete poured at the top of the opening.
The first charge of hopper shall be poured in hopper with bottom opening
temporarily closed by a steel plate placed at top of the opening. The hopper shall have
adequate capacity to receive the volume of concrete sufficient enough to displace drilling
mud within tremie pipe and from bottom of bore hole. After the hopper is filled up the steel
plate shall be quickly removed to allow concrete to rush into pile bore and fill it up from
bottom by displacing the drilling fluid from tremie pipe and the bottom of bore hole.
As the concreting progresses, the tremie pipes shall be removed in sections ensuring
every time that the bottom of tremie pipe remains embedded for atleast one metre (1m) into
concrete. Placing of concrete shall be done in one continuous operation and the tremie
pipes shall be held concentric with the bore hole.
In the exceptional case of interruption of concreting; but which can be resumed
within 1 or 2 hours, the tremie shall not be taken out of the concrete. Instead it shall be
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raised and lowered slowly, from time to time to prevent the concrete around the tremie
from setting. Concreting should be resumed by introducing a little richer concrete for easy
displacement of the partly set concrete.
Level of concrete shall be checked at frequent intervals to maintain a sufficient head
of concrete above the discharge end of mixes are poured to expel the fresh mix of concrete
contaminated with bentonite such that good concrete is obtained atleast up to 150mm
above the cut-off level. At all stages of concreting care shall be taken to prevent voids and
segregation in concrete.
The top of concrete in a pile shall be brought above the cut-off level to permit
removal of all laitance and weak concrete before capping and to ensure good concrete at
the cut-off level.
Withdrawal of casing:
Extraction of casing pipes shall be done in such a way that no necking or shearing of
concrete in shaft takes place.
Sequence of Piling:
Sequence of piling shall be such that there is no damage caused to concrete recently
laid in adjacent pile. Construction of pile should be done in accordance with the priority of
construction of various pile groups. Sequence of piling shall be decided by the consultant.
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Pile Cap:
A pile cap is a thick concrete mat that rests on concrete piles that have been driven into soft
or unstable ground to provide a suitable stable foundation. Load from the column gets
transferred to the pile cap. These pile caps can group one or more pile together. The pile
should project 50 mm into the cap concrete.
Finishing of Pile Heads:
Top level of concrete in the pile shall be brought up sufficiently above cut-off level
to allow for slumping or withdrawal of casing tube and also to have a minimum allowance
above cut-off level for removal of all laitance and weak concrete at top level. Any
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defective concrete at the head of completed pile shall be chipped off and made good with
new concrete bond with old concrete.
During chipping of the pile top manual chipping may be permitted after three days
of pile casting; pneumatic tools for chipping shall not be used before seven days after pile
casting.
Consumption of Concrete in Piling:
After completion, actual quantity of concrete shall be compared with the average
obtained from observations actually made in the case of few piles initially cast. The actual
quantity of concrete may also be worked out based on actual consumption of cement duly
certified by the Consultant. If the actual quantity is found to be considerably less, special
investigations shall be conducted and appropriate measures taken.
Defective Pile: In case, defective piles are formed, they shall be removed or left in place
whichever is convenient without affecting performance of the adjacent piles or the cap as a
whole. Additional piles shall be provided to replace them as directed.
Any deviation from the designed location alignment or load capacity of any pile
shall be noted and adequate measures taken well before the concreting of the pile cap and
plinth beam if the deviations are beyond the permissible limit.
BASIC PROPERTIES OF DRILLING MUD (BENTONITE):
Properties:
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The bentonite suspension used in bore holes is basically clay of Montmorillonite
group having exchangeable sodium cations. Because of the presence of sodium cations,
bentonite on dispersion will break down into small plate like particles having a negative
charge on the surfaces and positive charge on the edges. When the dispersion is left to
stand undisturbed, the particles become oriented building up a mechanical structure at its
own.
This mechanical structure held by electrical bonds is observable as a jellylike mass
or jelly material. When the jelly is agitated, the weak electrical bonds are broken and the
dispersion becomes fluid.
Functions:
The action of bentonite in stabilizing the sides of bore holes is primarily due to the
“Thixotropic property” of bentonite suspension. The thixotropic property of bentonite
suspension permits the material to have the consistency of a fluid when introduced into the
excavation and when undisturbed forms a jelly which when agitated become fluid again.
In the case of a granular soil, the bentonite suspension penetrates into the sides under
positive pressure and after a while forms a jelly.
The bentonite suspension gets deposited on the sides of the hole and makes the
surface impervious and imparts a plastering effect. In impervious clay, the bentonite does
not penetrate into the soil, but deposits only a thin film on the surface of the hole. Under
such condition, stability is derived from the hydrostatic head of the suspension.
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Specification:
The bentonite suspension used for piling work shall satisfy the following requirements:
The liquid limit of bentonite when tested in accordance with IS: 2720(Part V)-1965
shall be more than 300 percent and less than 450 percent.
The sand content of the bentonite powder shall not be greater than 7 percent. The
purpose of limiting the sand content is mainly to control and
reduce the wear and tear of the pumping equipment.
Bentonite solution should be made by mixing it with fresh water using pump for
circulation. The density of the bentonite solution should be about 1.12.
The Marsh viscosity when tested by a Marsh cone should be about 37 seconds.
The swelling index as measured by the swelled volume after 12 hours in abundant
quantity of water shall be at least 2 times its dry volume.
The pH value of the bentonite suspension shall be less than 11.5.
PILE LOAD TEST
Pile load test is the most direct method for determining the safe
loads on piles including its structural capacity with respect to soil in
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which it is installed. It is considered more reliable on account of its being
in-situ test than the capacities computed by other methods, such as
static formula, dynamic formulae and penetration test data.
Scope:
a) Vertical load test (compression),
b) Lateral load test, and
c) Pull-out test.
Types of tests:
There are two types of tests for each type of loading (i.e., vertical,
lateral and pullout).
Initial Test:
This test is required for one or more of the following purposes. This
is done in case of important and/or major projects and number of tests
may be one or more depending upon the number of piles required.
Determination of ultimate load capacities and arrival at safe load
by application of factor of safety,
To provide guidelines for setting up the limits of acceptance for
routine tests,
To study the effect of piling on adjacent existing structures and
take decision for the suitability of type of piles to be used,
To get an idea of suitability of piling system, and
To have a check on calculated load by dynamic or static
approaches.
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Routine Test:
This test is required for one or more of the following purposes. The
number of tests may generally be one-half percent of the total number
of piles required. The number of the test may be increased up to 2
percent in a particular case depending upon nature, type of structure
and strata condition:
One of the criteria is to determine the safe load of the pile;
Checking safe load and extent of safety for the specific functional
requirement of the pile at working load; and
Detection of any unusual performance contrary to the findings of
the initial test, if carried out.
Routine load tests on piles:
Routine load tests shall be carried out on selected piles after 28 days
of concreting in accordance with the specification and relative IS codes.
Procedure for Routine Vertical Load Test (Kentledge Method):
1. Excavation for the pile pit shall be done up to cut-off level with
keeping sufficient working area around the pile.
2. Pile to be tested shall be chipped off and dressed to natural horizontal
plane till sound concrete is met or up to cut-off level which is higher.
3. Top of pile shall be made level with sand or cement mortar.
4. Bearing plates of required thickness & size shall be placed on pile
head with centre coinciding the pile centre.
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5. Hydraulic jack of required capacity will be placed centrally on the
bearing plates of required thickness & size on the top of jack.
6. Main girders of required section (depend on the load test) shall be
placed on the test pile over jacks and bearing plates.
7. Both ends of main girder shall be placed on temporary supports,
made up of filled gunny bags or PCC. Main girder shall be placed level
& centre coinciding with the centre of the test pile.
8. Supports for secondary girders shall be made with filled gunny bags
at equal distance from the test pile centre according to size of
platform required, as per design. The height of support shall be
sufficient (min. 3-4” from the top of bearing plates to bottom
secondary girders) to allow bending of secondary girders due to
Kentledge.
9. Secondary girders of required section shall be placed cross & over the
main girder.
10.Kentledge consisting MS Billets/Blooms (3.7 MT wt.) shall be placed
symmetrically on top of platform as per requirement of Test load and
design.
11.Datum bars parallel to Main Girder, rested on fixed supports shall be
at a distance of 3D(subjected to a min. of 1.5m) from the centre of
pile on both sides, where D is diameter of pile.
12.Four numbers of Dial Gauges of 0.01mm sensitivity to measure the
settlement of the pile shall be fixed with datum bars and needle of
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gauge touching to the bearing plate placed on the top of pile. Small
glass piece shall below needle of dial gauge to get smooth surface.
13.After completion of all above arrangements, hydraulic lines shall be
connected to the jack and hydraulic pump attached with calibrated
pressure gauge to note the pressure at each stage of loading &
unloading.
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14.Loading on the test pile shall be commenced on the following manner:
The test shall be carried out by applying load in stages, each
increment being 20% of safe load on the test pile (exact
increment of load depends on the ram diameter of the jack &
least count of Pressure gauge).
For each stage of loading, the load shall be maintained till rate
of displacement of pile top is either 0.1mm in first 30 minutes or
0.2 mm in first one hour or till 2 hours whichever occurs first.
The pile settlement shall be noted at each stage of loading.
The full test load shall be maintained 24 hours and settlement
shall be measured at every one hour interval.
15.Unloading of test load shall be started after 24 hours of observation.
Unloading shall be done in same stages and rebound shall be
measured at each stage of unloading.
Recording of data:
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Complete records of boring and concreting process for each pile shall be
maintained:
1. Details of test:
Pile number and location.
Existing ground level, cut-off level and top of level of casting.
Nominal shaft and inside diameter of casing.
Date and time of start of boring.
Length of casing driven and depths bored vs. time.
Description and thickness of various strata encountered.
Details of any obstructions encountered (depth from existing ground
level, thickness and time taken to penetrate through the same).
Rock levels and time rate of boring through rock strata.
Final depth of boring (foundation level).
Standard penetration test at bottom of hole, if any.
Date and time of completion of boring.
Date and time of start and completion of flushing of borehole with
fresh bentonite fluid before concreting.
Time of lowering reinforcement cage and tremie pipes with total
lengths.
Date and time off start of concreting.
Nos. of mixes poured. Level of concrete inside the borehole and
length of tremie pipes at various stages of concreting.
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Concrete grade, mix proportion, water-cement ratio and slump test
results.
Empty boring length and concreted length below cut-off level.
Results of tests on bentonite slurry used.
2. Details of instruments used:
Specification of jack, pressure gauge and dial gauge.
Capacity of jack and Calibration of pressure and dial gauges.
Design load, description of location and identification marks of pile
for testing.
2. Test records: Records of settlement and rebound shall be entered
as per the proforma.
Procedure for Routine Lateral Load Test:
At the test level a concrete block shall be placed abutting against
the side of the excavation surrounding the pile allowing necessary gap
between the pile head and the concrete block to fit the hydraulic jack in
between. The hydraulic then shall be inserted in between the pile head
and the concrete block to apply lateral load at test level against passive
resistance of soil and weight of concrete block. Thrust blocks shall be
inserted on either end of jack to make up for gap.
Lateral deflection of the pile shall be measured at test level by
means of dial gauges fixed on immovable supports. The loading shall be
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applied in increments of about 20% of estimated safe load. Next
increment of load shall not be applied before deflection under a
particular load reduces to 0.02mm per hour. A load deformation curve
shall be plotted. The displacement shall be read by using atleast two
dial gauges of 0.01mm sensitivity spaced at 300mm apart and
interpolated at load point from similar triangles.
Assessment of Safe Lateral Loads:
The safe lateral load shall be least of the following:
Fifty percent of the final load at which the total horizontal
displacement increases to 12mm at test level.
Load at which total horizontal displacement corresponds to 5mm at
the test level
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Pull-Out Tests:
Pull-out load test on pile shall be conducted at proper locations and
levels. For this purpose, a test pit shall be excavated by an open
excavation through all types of soil upon the required depth and size.
The base of such a pit shall be of min. 3m x 3m size with adequate side
slopes with provisions for shoring and dewatering. The excavated
materials shall be dumped sufficiently away from the edge of excavation
so as not to endanger the stability of pit. The pit shall have adequate
side slopes with provision of shoring and dewatering. After completion of
the test, the pit shall be backfilled and compacted in layers.
Pull-out load test Set-up:
Uplift force shall be applied by means of hydraulic jacks fitted with
gauges using suitable pull out setup consisting of a structural framework
resting on two immovable supports. The jacks react against a frame
attached to the top of the pile such that, when the jacks are operated,
the pile gets pulled up and the reaction is transferred to the two
supports which are at 2.5D away from test pile edge (where D is the dia.
of pile).
The framework can be attached to the pile top with the
reinforcement bars, which may be threaded or to which threaded bolts
may be welded.
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Pull-out load shall be applied in a series of vertical upward incremental
load, each increment being 20% of the estimated safe pull-out load
capacity or 1t whichever is less. Upward movement of pile shall be
recorded with three dial gauges of min. 0.1mm sensitivity and held by
datum bars resting on immovable supports.
Assessment of Safe Loads:
The safe pull-out load shall be taken as the least of the following:
Two-thirds of the load at which the total displacement is 12mm.
Half of the load at which the load displacement curve shows a clear
break.
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Integrity Testing on Piles:
Purpose:
In addition to the static load tests to be carried out as specified in the
foregoing integrity testing of piles also known as low-strain testing shall
be conducted on a number of selected piles to detect any pile defects,
and pile health parameters like voids, cracks, soil inclusions, necking
and diameter changes. To determine Integrity of pile in its total length and the
unknown length of pile in existing structures
Pile preparation for the test: The pile head must be clean,
accessible, sound and free from standing water. The test shall be
conducted on a pile which has been cast at least 7 days before.
Equipment for testing: The tests shall be performed with a small
impact device (a small 6 pound spring loaded nylon tipped hand held
hammer), sensitive accelerometer, special purpose, PIT collector and an
output device like a plotter or graphics printer which shall be provided
by the Consultant for carrying out the least at site.
Method of Testing: The accelerometer will be attached to the pile top
using a viscous material. Low strain compressive impact waves will be
generated by tapping the pile with the top of the hammer. When the
downward travelling compression wave encounters a change in cross-
section or in concrete quality, it generates an upward travelling tension
wave which later is observed at the pile top. The low strain compressive
impact wave and its reflections will be sensed by the accelerometer.
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The signal will be converted into a velocity measurement, presented on
a screen as a function of time and stored. The velocity records along
subsequent reflections rom either the pile top or from pile
discontinuities shall be graphically displayed, output directly to a plotter
or/and transferred to a disk.
Interpretation of test Results and Reporting:
Analysis to be submitted shall be carried by exponential
amplification of the signal with the time and the average velocity curve
obtained by numerically integrating the acceleration record.
The test and its interpretation shall be conducted by specialized
agency or persons specially equipped and trained for the purpose by the
manufacturer of the testing equipment.
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CONCLUSION
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CONCLUSION
The piling and civil works for expansion of Rolling Mills, RINL VSP were
observed. It was learnt that the soil investigation was initially conducted by taking bore log
samples and further analyzing for the safe bearing capacity of the soil across the mill. After
the design data and drawings were obtained, the construction commenced at the site.
Initially pile boring was conducted using rotary pile driving rigs. The sides of the borehole
are stiffened by pumping bentonite slurry. After flushing the bentonite slurry the
reinforcement cage was lowered and subsequently followed by casting concrete. Later on
the dead concrete of about 750mm above the cut-off level was chapped and the bars are
bent for casting the pile cap. Before the construction of pile caps, pile tests are conducted
on a number of piles. If there is any defective pile, an additional pile is constructed beside
it based on the design. Subsequent structures like pile cap, pedestal and walls were
constructed.
All necessary safety and quality stipulations are ensured at the site for better
working at site.
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BIBLOGRAPHY
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BIBLOGRAPHY
IS 2911 : Part 1 : Sec 2 Bored cast-in-situ piles
IS 2911 : Part 4 : 1985 Load test on piles
IS 456 : 2000 Code of practice for RC Structure
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