Method Statement Crane Copy

7/31/2019 Method Statement Crane Copy

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METHOD STATEMENT FOR INSTALLATION

OF BORED CAST IN-SITU PILES USING CRANE

MOUNTED DRILLING UNITS

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PROPOSED METHOD STATEMENT

FOR INSTALLATION OF BORED CAST IN-SITU PILES

AT CREEK MARINA

USING CRANE MOUNTED DRILLING UNITS

1. GENERAL: 1200mm and 550mm diameter bored cast in situ piles require to be

constructed at the Creek Marina project. Following is our proposed method statement.

2.

CONSTRUCTION OF PILES:

2.1 Equipment: The piles will be drilled utilizing crane mounted pile diggers.

Suitable service cranes will be deployed to handle the tremie concreting and

the cage lowering operations.

2.2 Setting Out: The pile centre will be established from baselines / benchmarks

provided by the main contractor / engineer. Reference pins will be placed at

90o to offset the position of the pile centre. These reference pins will then be

used to periodically confirm the centre of the pile during the constructionoperations.

2.3 Drilling : The rig will set up over the pile centre pin and the verticality of the

Kelly bar will be checked with a spirit level to ensure verticality of the

borehole. The drilling unit will bore a pilot hole approximately 20mm larger

in diameter than the diameter of the pile being installed. A temporary casing

approximately 2-3 meters long, which will be kept true to the centre of the pile

by checking from the reference pins, will be installed in this pilot hole.

Bentonite will be then be entered into the pilot hole (if required), for thestability of the borehole, and the drilling of the bore will be continued with

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appropriate digging tools until all soil down to the tip of the pile has been

removed. After this operation the bottom of the bore will be cleaned out using

a purpose made cleaning bucket (if required) which will remove all loose

material for the bottom of the bore.

2.4 Recycling of Bentonite : Prior to the cage lowering and concreting operations

the bentonite sand content in the borehole will be checked. Depending on the

sand contamination the bentonite will be recycled. This recycling operation

will continue until the sand content in the bentonite is within required limits.

Contd..P/2

2.5 Steel Reinforcement Cages: The pre-fabricated reinforcement cage, complete

with roller spacers, will be placed within the bore by the service crane, and

checked for level from the adjacent benchmarks. Before placement of thesteel cage the bottom of the borehole will be checked for the correct depth.

The reinforcement for each pile shall be assembled on ground and securely

tied by means of binding wire / welding in such a manner as to form a rigid

cage. Concrete spacer blocks shall be securely attached to the reinforcement

at a suitable spacing in such a manner as to ensure that the concrete cover

stipulated on the drawings is maintained throughout and that the

reinforcement cage is not displaced in the borehole in the course of

subsequent concreting operation. Particular care shall be taken to ensure that

in general, there are no obstructions of any kind inside the reinforcement cagedue to spacer blocks or lapped reinforcement or any other reason, which might

interfere with smooth travel of the concreting tremie.

2.6. Concreting: Before the start of the concreting operations all instrumentation /

pipes etc. required for the subsequent testing / grouting of the piles as

required, will be placed and secured within the borehole, to the required

depth / elevations. Concrete will be produced using batching plant and will be

brought to the pile head in transits. Concrete shall be placed by means of a

tremie lowered and raised by the service crane. The outer dimensions of thetremie pipe shall be such that it can be freely lowered and raised inside the

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reinforcement cage. The manner of lowering and raising the tremie shall be

carefully controlled so as to ensure that the reinforcement cage is not distorted

or displaced during the course of concreting. Prior to the start of the

concreting the tremie shall be lowered to the bottom of the borehole.

Concrete of the specified proportions will then be placed through a full-lengthtremie. During the concreting operations sufficient embedment (2-3) meters of

the tremie shall be maintained in the concrete. The concrete being poured will

have a slump of 180mm and its initial set will be retarded by 1 (one) hour, by

use of suitable admixture. The concrete operation will end when the green

concrete has reached the pile cut off level. If the pile cut of level is below

platform level then the concrete will be brought up to the required level above

the cut off level. The 2-3 meter long temporary casing will be extracted at the

end of the concreting operation.

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Documents

Method Statement Crane Copy