Methodology of Board pile foundation in cast in situ method

1. Method Statement for the Construction of Bored Pile
Presented By: DK Singh

2. SCHEMATIC CONSTRUCTION SEQUENCE OF BORED PILES USING ROTARY RIG

3.  GENRAL
This method statement describes the procedure, the construction procedure, the materials and
equipment required for the construction of bored – piles. The intention of the method statement is to
give a general guideline for the construction work. Details of the procedures contained herein may be
modified based upon actual site requirement.
*TYPE & METHOD OF CONSTRUCTIONOF PILEBORED CAST-IN-SITU (BCIS)*
 BCISWITH ROTARY RIG

4.  WORKING PLATEFORM
I. The piling work will be carried out from the working platform level.
II. The working platform will be made with suitable material by the Main Contractor for the movement of
equipment & ready-mix trucks.
 CONSTRUCTION OF PROCEDURE
The procedure for the construction of approval of bored piles, with temporary casing under Bentonite
slurry system, comprises the following elements:
A. Setting up the Pile position.
B. Installation of temporary guide casing.
C. Drilling of the pile borehole.
D. Recycling.
E. Reinforcement cages in the stallion.
F. Concreting.
G. Removal of temporary guide casing.

5.  Setting out of Pile Position
• A qualified full-time surveyor from the Main Contractor will be engaged for setting out of the pile
positions using the coordinate system.
• The pile points will be marked by fixing steel pegs in the working platform. After checking the pegs will
be driven into the ground to protect them from any disturbance.
• Any pile points, which is disturbed by machinery movement, soil movement etc. will be reset.
 Installation Of Temporary Guide Casing
• A Temporary guide casing having an internal diameter same as pile diameter shall be installed to the
pile center as previously marked on the working platform.
• The temporary guide casing shall be uniform section throughout the length.
• The casing shall consist of a series of lengths, which will be joined together to extend the length if
necessary.
• The verticality of the steel casing is checked with a spirit level in two perpendicular directions.

7.  Drilling of Pile Borehole
•After the installation of the temporary casing, the borehole will be drilled using appropriate drilling tools.
The borehole will be drilled under Bentonite slurry support for the borehole stabilization.
•The drilling fluid is prepared in mixers and kept in tanks for storage and hydration purpose.
•After fixing of the guide casing, the borehole will be drilled down to its final level by means of bucket
and auger.
•The Drilled borehole will be filled with Bentonite slurry and the slurry level maintained at the working
platform level at all times. In case of any rapid loss of drilling fluid, the borehole will be backfilled without
delay using the drilled material from heap near the borehole.
•When the designed depth has been reached which approved by the consultant, the base of the
borehole will be cleaned with a cleaning bucket.
•Control tests will be performed on the Bentonite suspension as per specification using a suitable
apparatus.
•A sample of the Bentonite suspension will be taken from the base of the boring using an approved
sampling device.
•Flushing of borehole will be carried out by using 220mm diameter tremie pipe connected to the mud
pump. The fresh Bentonite will be pumped to the bottom of the borehole, where another pump will be
used to discharge the overflow Bentonite to the de-sanding plant.
•When flushing completed another sample of the Bentonite suspension will be taken from the base of
the boring. The gravity of the suspension should not exceed 1.25.

8.  Recycling
 The process of cleaning Bentonite from sand & silt to keep its quality within the allowable limits is
called Recycling.
•Recycling will be performed after boring has been completed and the Bentonite has been replaced by
concrete.
•The Bentonite from the borehole will be pumped to the de-sanding plant during concreting.
•After that, the Bentonite will be pumped to the tanks for further use.

9.  Bentonite slurry will have the following properties:
In order to achieve a concentration of 5%, 50 kg of Bentonite will be added to approx.1000 liters of
water. Mixing will take place in a mixing plant. The Bentonite shall rest in the tanks for at least 4
hours to allow the proper hydration.
Specified Limit for Polymer& Bentonite:
Sr. No. Material
Density
(g/cc)
Ph Value
Marsh Cone
Viscosity(Sec.)
Sand
Content
(%)
Remarks
1 POLYMER
1.00
to1.14 9.0 to 12 40 to 80 Seconds < 7%
2 Sodiam According Ph Value of of polymer mixer it should not more than1 ltr/ m3.
3 BENTONITE
1.04 to
1.12 9.0 to 12
30 to 90
Seconds < 7% Bentonite Kg/ 4 to 6% by weight of water

10. Reinforcement Cages Installation
I. FABRICATION OF STEEL CAGE. Prior to the installation, steel cage will be pre-fabricated at the
bending yard by skilled bar bender as per approved design & drawings. After the fabrication has
been completed, the steel cages will be linked using D-Shackles at the top and bottom of the
steel cage. Hanging supports will be provided to the main reinforcement at the top of the cage to
facilitate lifting using the same method.
II. LOWERING OF THE REINFORCEMENT CAGE. Prior to the placing of concrete, the borehole
depth will be checked. The approved reinforcement cage will be lowered into the borehole to the
correct level by means of a service crane. The site datum level will be given to ensure the correct
positioning of the cage in respect to the cut off level. Correct positioning of the cage within the
borehole will be ensured by the use of a Concrete spacer as per approved sample, properly
provided to achieve concrete cover of 100mm during concreting. To keep the steel cage in place
and at the correct levels, the cage will be hanged to the temporary casing until the concreting is
finished.
III. CONCRETE PLACEMENT. For Concreting operation, separate Tremie pipe sections of diameter
220mm will be joined and lowered, one by one into the borehole until the end of the pipe just
contacts the bottom of the borehole. The tremie pipe will then be raised up by 150mm to facilitate
the flow of concrete.

12. Porbandar-Dwarika Express way Project

13. Concreting
 The concrete is delivered to site by means of truck mixers. The concrete will be checked for the slump
and temperature. Cubes will be taken as per specification. The concrete will be allowed to the site only
after concrete quality has been found in compliance with specifications.
 The concrete shall be poured by using concrete pump connected to the Tremie pipe by 90 degrees L-
bow without interruption to prevent hardening of the previously placed batch. The Tremie is made up of
sections with sufficient length to reach the toe of the pile and the joints provided with seals.
 The Tremie pipe will be inserted at the center of the pile to reach up to the toe. The Tremie will be lifted
100mm above pile toe level prior to concreting. While concreting the length of the Tremie pipe will be
shortened if necessary, however,
 the Tremie pipe will be maintained full time into the concrete of at least 2.0m length. During the
concreting, the level of the concrete will be monitored by use of an end weight tape measure. A sufficient
quantity of concrete will be maintained within the Tremie to ensure that the pressure from it exceeds that
from the Bentonite slurry.
 The concrete will be brought up to the working level at least 1.0m above the cut-off level to ensure good
quality and contamination free concrete at pile cut-off level.
 The Bentonite slurry displaced by the concrete will be pumped back to the de-sander. The concrete
above cut-off level will be chipped by the Main Contractor.

14. Extraction of Temporary Casing
On completion of the concreting operation, the temporary casing will be withdrawn by piling rig.
When the casing will be extracted, a sufficient quantity of concrete will be maintained within it to
ensure that pressure from external water, Bentonite slurry or soil is exceeded and that the pile is
neither reduced in section nor contaminated.

16. Load Test
No. of working pile load test to 1.5 times the working load.
Working load is (state the pile capacity as per soil report in KN) for _ Nos. of (pile diameter) mm
diameter in working bored piles.
All Piles shall be integrity tested.
Production rate will be estimated around (specify no. of piles) piles per day.

17. Thanks for given us your valuable time
Jay Hind