bored pile_method statement

8/17/2019 Bored Pile_Method Statement

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Surveying

Install casing

Drilling

Remove slime

Install rebar cage

Install tremie pile

Concreting

Toe grouting/ Cutting off

Completion

Preparation of

reinforcement bars and

circular cover block

Earthork

!ithdra tremie pipe and

casing


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"ET#$D ST%TE"E&T '$R T#E C$&STR(CTI$& $' )$RED PI*ES

+, E-cavation of pile shaft

. #ydraulic rig/manually operable auger should be mobilied at the re0uiredlocation,

. Set out the correct position of the bored pile on site

. Set up a orking platform to the top of the temporary casing if the ground is soft

using steel plates

. E-cavate in soil using augering method, The auger is loered don by a

telescopic boom to e-cavate soil and retrieve the auger to the top after e-cavation. "ove the auger ith soil in it aay from the e-cavated hole by singing the

machine, Rotate the auger in the opposite direction to remove the soil from the

auger

o Drilling shall be done up to 1 to 2 meters depth using 344 mm diameter

auger and the temporary casing of length + to 5 meter driven directly

through the rotary head,

o Set up the vibrator in lifted ith a crane

o Install the bottom section of permanent or temporary casing into the

ground by vibrating motion e-erted by the vibrator

o 6erticality of the casing ill be monitored by means of spirit level 7th89c

th:y;

. Depending on soil condition< if necessary< Drilling mud 7)entonite; shall be used

for the stabiliation of pile .bore sides in addition to temporary casing herever

subsoil = ground ater conditions are likely to cause mud flo or instability of

pile bore,. )entonite used to stabilie the sides of bore hole should be conforming to

re0uirements as listed in inspection and test plan, Density of bentonite solution

should be checked during boring operation to ensure that the density is about +,4>

g/cc to +,+4 g/cc< marsh cone viscosity 14 to 24 and p# value ?,> to +5,. The pile shaft shall be cleaned by the bucket if there are suspected loose material

at the toe, The presence of ater in the shaft 7if any; is $@< provided there are no

collapse of soil in the hole,

. This can be checked ith hen the ithdraal of bucket< there shall be no debris<

soils or rock fragments in the bucket after cleaning

. The depth of the pile is checked using a eighted measuring tape 7sounding

chain;

5, Reinforcement cage loering. Prefabricated reinforcement cage prepared as per the draings and approved

depths< is brought and kept near pile location hile boring is in progress,

. %fter getting the permission from the engineer< the reinforcement cage ill be

gently lifted and loered by crane/manually into the bored hole, &ecessary


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concrete cover ill be obtained by using the circular cover blocks already made

of the same strength as of pile,

. The eight of the prefabricated cage can be calculated in order to select a suitable

crane for lifting, If a mechanical bored pile machine is used< the bore pile machine

engine shall be detached and the mounted crane can be used for lifting,

. The prefabricated cage shall be loered don into the hole< segment by segment by lifting the entire cage using a suitable crane, The top of the cage ill be elded

ith a suitable hook for lifting of the cage,. Shall lapping of reinforcement is needed< a lap length of 24D shall be used, The

laps shall be done using elding< or tied ith tie ires or (.bolts,

. Repeat the step above until re0uired depth is reached

. It is to be checked hether the reinforcement cage has reached up to bottom of

the pile by measuring from the top of the cage to the ground level,

1, Tremie pipe fi-ing and flushing

. %fter cage loering< 544 mm diameter tremie pipes in suitable lengths are to be

loered in the hole, The operation is done by loering one tremie pipe after

another and connecting them threading to maintain ater tightness throughout its

length till the gap beteen the pile base and Tremie is beteenA> B +44 mm, the

tremie pipe is locked/supported from top to maintain the level and funnel is

attached on top,. The vacuum length beteen Tremie pipe end and the borehole end shall not be

more than 4,1m, Proper record shall be maintained to monitor the Tremie fi-ing =

removing procedures,

. 'inally the "S hopper of 4,> to 4,A> Cum capacity shall be fi-ed at top,

. %fter completion of loering Tremie pipes< flushing shall be started, 'resh

)entonite solutions of specific gravity +,4> to +,+> shall be used for flushing, It

shall be continued until the specific gravity of e-it )entonite solution at the bottom of pile comes belo +,54gm/cc, 7The tremie head to be provided to the

tremie pipe for the flushing activity, The bore is flushed by fresh bentonite slurry

through the tremie head, The pumping for flushing is done by use of mud

circulation pump, 'lushing ill be done to remove all the loose sediments hich

might have accumulated on the founding strata, 'urther< the flushing operation

shall be continued till the consistency of infloing and out floing slurry is

similar;2, Pile Conceting

. Determination of the density of the drilling mud from the base of the borehole

shall be carried out by taking samples of fluid by suitable slurry sample approved

by the engineer in charge< in first fe piles and at suitable interval of piles

thereafter and the results recorded,

. The slump of the concrete ill be maintained at +>4 mm to 544 mm,

. Concreting operation ill be carried out using the 544 mm diameter trmie pipes

. Concrete ill be poured into the tremie pipe by using a concrete skip

. Initial charge of concrete should be given in the funnel using a plug, Total

concrete 0uantity in the funnel should be more than the volume of the entire pipe


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plus free space belo the tremie, This ill ensure a ater tight concrete pouring

through tremie

. The concrete is poured in the funnel, %s the concrete reaches the top of the funnel<

the plug is lifted up to allo the concrete to flo corresponding to the placing of

each batch of concrete,

. *ifting and loering is repeated keeping sufficient concrete in funnel all the time,%s the concreting proceeds the tremie pipe are to be removed one by one< taking

care that the tremie pipe has sufficient embedment in the concrete until the hole

pipe is concreted, Sufficient head of green concrete shall be maintained to prevent

inflo of soil or ater in to concrete, Placing of concrete shall be a continuous

process from the toe level to top of pile,

. The concreting of pile is to be done up to minimum of 144 mm above the cut off

level to get good and sound concrete at cut off level,

. %fter completing the pile concrete< the hopper and the Tremie pipes shall be

removed and cleaned properly, Casing shall be removed immediately or before

initial setting time by using a crane/piling rig,.

*IST $' "%C#I&ER = E(IP"E&T

Drilling Rig ith re0uired diameter of drilling toolsF

Temporary guide casingF

Tremie pipe of +G4/5>4mm dia ith lifting head< flushing head and hopper etc,F

"i-ing and circulation of drilling mudF

)entonite mi-ing unitF

Pump for drilling mudF

Diesel generatorF

!elding machineF

Testing kit for drilling mudF

Service craneF

)atching plantF

Transit mi-erF

Survey instrumentF

"%TERI%*S


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Cement.$PC >1.Hrade B IS.G++5/IS.+553?

Reinforcement Steel 'e.>44 B IS.+AG3F

Coarse %ggregate Table.5 of IS.1G1

'ine %ggregate Table.2 of IS.1G1!ater as per IS.2>3

)entonite as drilling mud %ppendi- % of IS.5?++ PartB+.SecB5< If the soil condition

permits only this shall be used,

Concrete "i- ".5> 7Design "i- shall be submitted separately for approval;F

'ly ash and admi-tures if re0uired as per IS.2>3 and shall be submitted during design

mi-F

"aterial and products

Requirements for material

Bentonite


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Concrete

. The ma-imum sie of the aggregate shall not e-ceed 15 mm or of the clear

space beteen the longitudinal bars< hichever is the smaller,

. !hen aggregate sie is smaller than 2mm< cement content should be increased,

. The ater/cement ratio shall not e-ceed 4,3

. Concrete for bored piles shall

o #ave a high resistance against segregation

o

)e of high plasticity and good cohesivenesso 'lo ell

o )e ade0uately self.compacting

o )e sufficiently orkable for the duration of the placement procedure<

including the removal of any temporary casings


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. 'or long concreting operation of the piles< a minimum slump of +44mm after 2h

is common practice

. Sampling and testing on site

o %ll sampling and testing of fresh concrete on site shall comply ith E&

13A4 and the e-ecution specification,

o The minimum number of cylinder or cube specimens in a sample is three

Reinforcement

. The reinforcement steel cages used in bored piles shall comply ith E& +44G4

. The lap of bars should be located aay from the ma-imum bending area

Execution

+, Heometrical tolerances

Heometrical tolerances

Plan location of vertical bored piles

referenced to the orking platform level

ma- 4,+e e m≤ =

'or bored pile ith D or ! ≤ +,4m

Deviation of inclination of vertical bored

pile ith an inclination of4+>7 G3 ;n θ ≥ ≥

ma- 4,457 4,45 / ;i i m m≤ = A

Deviation in plan of centres of

enlargements in relation to the bored pilema- 4,+ 7 ;e e D orW ≤ = ×


8/13

a-is

Installation tolerances for reinforcement cage

. (nless otherise specified< the elevation of the top of the cage after concrete placement shall be e0ual to the nominal value ith a ma-imum deviation of

.4,+>m to J 4,+>m

Tolerances for trimming

. )ored pile trimming and cutting.off shall e-ecuted such that a construction Koint

ith ma-imum deviations of J4,42m/.4,4A m at the design cut.off level is

formed,

5, E-cavation

. !hen constructing bored piles measures shall be taken to prevent uncontrolled

inflo of ater and/or soil into the bore

. In soils liable to flo into the bore or here there is a risk of collapse< means of

support shall be used to maintain stability and thereby prevent the uncontrolled

entry of soil and ater, Some common means of support of bore alls are

o Casings

o Support fluid

o Soil.filled auger flights

. )ored pile bores shall be e-cavated until they reach

o The specified bearing stratumF or

o The anticipated founding level

. Completed e-cavations shall be left open only for the time necessary to allo

o Cleaning and/or desandingo The various checks< and

o Installation of reinforcement< if any

. !here bored piles are constructed in ground hich is likely to deteriorate ith

time and it is not possible to finish the bored pile by the end of the orking day< a

depth e0uivalent to the folloing number shall be bored the folloing orking

day immediately before concrete placement

o %t least tice the shaft diameter< but

o &ot less than +,>m

. If a bored pile encounters an impenetrable obstruction prior to reaching its

designed founding depth< the design specification shall be revie. The center to center distance for bored piles produced ith a time.difference less

than 2 h should be at least four times D or ! ith a minimum of 5 m

. Disturbed soil< debris or any other material that could affect the bored pile

performance shall be removed from the base prior to concrete placement

7cleaning of bases;

"ethods and tools


9/13

. )ored piles can be e-cavated in an intermittent or continuous process

. The type of boring tool shall

o )e appropriate to the given soil< rock< groundater or other environmental

conditions

o )e selected ith a vie to preventing loosening of material outside the

bored pile and belo its baseF ando %llo the bores to be e-cavated 0uickly

E-cavations supported by casings

. Casings may be installed during the e-cavation process using

o $scillatingF or

o Rotating e0uipmentF

. $r they may be driven prior to the e-cavation using

o Piling hammersF or

o 6ibrators or other,

. Construction techni0ues involving casings shall allo their safe installation andsubse0uent recovery during or after the concreting process< unless casings are

re0uired to be permanent< for that purpose

o Casings shall be cylindrical and ithout any significant longitudinal or

diametrical distortion

o Casings shall be designed to ithstand the e-ternal pressure and the forces

of installation and recovery

o Temporary casings shall be free of significant internal proKections or

encrusted concreteF

o Casing Koints shall permit the transfer of longitudinal forces and torsion

moments ithout significant play

. !here a bored pile is e-cavated in the folloing conditions< an internal e-cess

pressure shall be provided ithin the casing by a head of ater or other suitable

fluid of not less than +


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o In special circumstances 7for e-amples in the case of loose sand or soft

soils;< it can be necessary to raise the level of the support fluid,

. %n ade0uate supply of support fluid shall alays be kept available to cater for

regular consumption and any potential loss of suspension into the ground

. In cases of sudden outflo of fluid from the e-cavation< it can be necessary to

backfill the bore. The operating velocity of the tool shall be controlled and adKusted as necessary in

order to avoid a LpistonM effect that can affect e-cavation stability,

Reinforcement

. Steel reinforcement shall be stored in clean conditions and shall be clean and free

from loose rust< and loose mill scale at the time of installation and concreting,

. Reinforcement cages shall be suspended or supported so as to maintain their

correct position during concreting. Noints in reinforcement bars shall be

o Such that the full strength of each bar is effective across the KointF and

o Constructed such that there is no detrimental displacement of the

reinforcement during construction of the bored pile

. Reinforcing bars shall not be elded at or near bends

. The assembly of cages and the fi-ing together of bars shall be such that

o Cages can be lifted and installed ithout permanent distortion

o %ll bars remain in the correct position,

. Spacers shall be arranged symmetrically around the cage ith

o %t least three numbers at each level

o %t level intervals of not more than 1


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. If the bore contains a support fluid< the properties of the fluid shall be checked

before concrete placement

. %n ade0uate supply of concrete shall be available throughout the placement

process to enable a controlled smooth operation,

. Internal vibration is not permissible for the compaction of the concrete,

. %ppropriate precautions shall be taken to prevent the fines of the concrete beingashed out from the shaft surface by floing groundater,

. Concreting shall be carried out in such ay as to avoid segregation,

. During the concreting the volume placed and the level of concrete inside the bore

shall be checked and recorded,

. The levels shall be checked at least once

o %fter every pourF or

o )efore or after a temporary casing is lifted,

. The height of the casting level above the cut.off level should be increased hen

o The cut.off level lies deep belo the orking platform

o Concreting is carried out in submerged conditionsF or

o Temporary casings are recovered. !hen the final casting level is belo the orking platform< the fresh concrete

should be protected against contamination from above

o )y concreting above the cut.off level

o )y backfilling the empty bore ith suitable materialF or

o )y maintaining a support fluid inside the empty bore until the concrete has

set

Concreting in submerged conditions

. Concreting shall proceed only hen the properties of the suspension are

satisfactory, $therise additional recycling and cleaning or substitution of thesuspension is necessary,

. In order to avoid mi-ing beteen concrete and bentonite< the instantaneous

velocity of concrete rising should not be less than 1m/h. !here concreting is carried out under ater or a support fluid< the consistency

shall be in accordance ith table 2 and a tremie pipe shall be used for the

placement, The main purpose of the tremie pipe is the prevention of segregation

of the concrete during placement or its contamination by the fluid inside the bore,

. The tremie pipe< including all its Koints< shall be ater tight,

. The tremie pipe shall be smooth to allo free flo of concrete and have a uniform

internal diameter of at least the greater of the folloing numbers

o Si- times the ma-imum sie if the aggregateF or

o +>4 mm

. The tremie pipe shall be e0uipped at its upper end ith a hopper to receive the

fresh concrete and prevent spillage of concrete hich otherise could fall freely

into the bore< segregate or become contaminated,

. The e-ternal shape and dimension of the tremie pipe< including its Koints< shall

allo its free movement inside the reinforcement cage,


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. The e-ternal shape and dimension of the tremie pipe< including its Koints should

be not more than

o 4,1> times the pile diameter D or the inner diameter of a casing

o 4,3 times the inner idth of the reinforcement cage for pilesF and

o 4,G times the inner idth of the reinforcement cage for barretes

. The tremie pipe shall be cleaned of all encrusted concrete or mortar prior to itsuse,

. The tremie pipe shall e-tend to the bottom of the bored pile at the commencement

of the concreting

. % bung or plug of suitable material< to prevent mi-ing of concrete ith any fluid

in the tremie pipe< shall be inserted into the pipe before the commencement of

concrete placement,

. %s the first batch< a cement enriched mi- or a charge of cement mortar may be

used to lubricate the tremie pipe,

. To allo the first concrete to leave the tremie pipe< the pipe shall be lifted slightly<

not e-ceeding a value e0ual to the inner diameter of the tremie pipe, Placement

shall then proceed 0uickly to fill the entire base of the bored pile so that no

concrete hich may have segregated at the beginning of the discharge is trapped,

. During subse0uent placement the tremie pipe shall be ithdran progressively as

the concrete rises in the bore,. The pipe shall at all times remain immersed in unset and orkable concrete hich

has previously benn placed and shall not be ithdran from the concrete until the

completion of the concreting process,

. The immersion of the tremie pipe into the concrete should be not less than +m <

particularly hen disconnecting sections of the pipe and hen recovering and

disconnecting sections of temporary casing,

. 'or piles ith a diameter DO +,5 m the immersion should be at least 5,>m andfor barrettes at least 1


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. During the continued e-traction a sufficient 0uantity and head of concrete shall be

maintained inside the casing to balance the e-ternal pressure so that the annular

space vacated by the removal of the casing is filled ith concrete,. The supply of concrete and the speed of e-traction of the casing shall be such that

no inflo of soil or ater occurs into the freshly placed concrete< even if a sudden

drop of concrete level should occur hen a cavity outside the casing is uncovered,. Since the top of the cast concrete may not be of the re0uired 0uality< sufficient

concrete shall be placed in the bore to ensure that the concrete belo the cut.off

level has the specified properties,

. The trimming shall eliminate the polluted and/or dirty concrete and a minimum of

sound concrete above the cut.off level over the full cross.section of the pile

. Trimming of the concrete to cut.off level shall be carried out using e0uipment and

methods hich ill not damage the concrete< reinforcement or any

instrumentation installed in the pile

. !here possible< some trimming above cut.off level may be carried out before the

concrete has set,. 'inal trimming to cut.off level shall only be carried out after the concrete has

gained sufficient strength,

. Pile edges broken belo the cut.off level shall be kept clean,

.

bored pile_method statement

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