Construction method statement of bored pile

Construction method statement of bored pile
1. Flow chart :
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Preparation work
Setting out of pile
(Inspect center point)
Preliminary drilling
Install temp.casing
(Inspect center pile)
Boring work
Preliminary cleaning
(Inspect bored hole)
Mix bentonite
(Inspect bentonite)
Install rebar cage
(Inspect connection)
Fabricate rebar cage
(Inspect rebar)
Air lifting cleaning
(Inspect bentonite)
Pouringconcrete
Remove temp. casing
Backfill over pile
End
2. List equipment :
List of major construction equipments will use for pilling work :
No. Name of equipment Number Used for Remark
1 Drilling equipment DH350-5 01 each Drilling hole
2 Backhoe 0.8m3 01 each
Excavate
Exis.pavement

3 Dumptruck 12m3 03 each
Disposal of
soil
4 Mix truck 05 each Concreting
5 Air compressor Denyo 01 each Cleaning hole
6 Sand Sieve 01 each
Separation
sand and
betonite
7 Bentonite mixing system 01 set
Mixing and
treating
bentonite
Including
tanks
8 Tremipipe pipe D =300mm, L = 56 m 01 set Concreting
1m x 2pcs
2m x 2 pcs
3m x 12 pcs
9 Air compress pipe D=90mm L = 56 m 01 set Cleaning hole 6m x 7 pcs
10 Bending machine 01 each Rebar
11 Cutting machine 01 each Rebar
12 Water pump 6 inch 02 each
Recover
bentonite
13 Water pump 4 inch 02 each
Supply
bentonit
14 Water pump 2 inch 02 each Serving
15 Casing D1100, t=10mm L = 6m 02 each Boring

16 Drilling bucket D1000 02 each Boring
17 Cleaning bucket D1000 02 each Cleaning
18 Steel plate 1,5x6x0.01m 4 sheet
Support
machine
19 Generator 125KVA 1 Unit Supply power
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3. Detailed method statement :
3.1 Preparation work:
Preparation works are including:
- Shop drawing of bored piles is approved by the Consultant .
- Bored pile construction sequence, operation area of drilling machine team,
equipment movement chart conforms to construction schedule of each bored pile
- Preparation of manpower and equipments for construction work
- Preparation of materials (mixed concrete, rebar, bentonite, and other materials)
- Preparation of test instrument : slump, bentonite liquid, depth of boring hole,
diameter of bored pile,...
3.2 Setting out bored pile
Center point of every bored pile is set out exactly by total station base on coodination
of the designed location. After set up the center point, the off-set point will make to keep
enough distance from boring pile.
3.3 Preliminary drilling
After mark the off set point, it will start the excavation for checking the obstruction
structure and underground utility by using adequate equipment and manpower. The initial
excavation will execute up to 1.5m from the existing ground.
The preliminary drilling will execute by using the drilling device with drilling bucket
attachment for installing of the temporary casing. The attachment device will check the
center point and vertical.
3.4 Installing of temporary casing
After preliminary drilling, it will install the temporary casing up to the preliminary

drilling elevation. The diameter of the temporary casing is 10cm bigger than the design
diameter. Length of the temporary casing will use 6m.
Contractor will check the location and verticality of the by survey. Incase the location
and verticality is not satisfy the specification, it will re-install the temporary casing. After
installing the temporary casing it will start the backfill and compaction around the
temporary casing.
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3.5 Boring Work
Before starting the boring work, it will pour the bentonite slurry into the bore hole.
The level of the bentonite slurry will be kept more than higher of the ground water level to
avoid the collapse in the bore hole.
The boring work will use the drilling bucket. The speed of the bucket will be as the
lifting is about 0.5m/s and lowering is about 1.5m/s
The boring soil will stock near the hole. The stock soil from the bore hole will be
loading to the dump truck by using the backhoe and disposal out of the project.
will check the verticality and soil condition during the boring time.
When the boring reaches the bearing layer, will request the inspection of the bearing
layer to consultant.
3.6 Preliminary cleaning of boring hole:
After boring, it will change the bucket from drilling to cleaning. Contractor will check
the requirement depth of the bored hole. After checking, it will wait the next work for
monitoring the sedimentation for approximately 20-:-30 munites. Contractor will check the
depth of the bored hole again. In case it has the more than 20 cm of sedimentation in the
bored hole, Contractor will execute the cleaning work by using the cleaning bucket.
3.7 Bentonite slurry control :
Contractor will use and control the bentonite slurry for protection the collapse in the
bore hole during the boring work. The design mix of bentonite slurry is as following the
table. The mix of the bentonite slurry will use the bentonite mixing system.
Design mix of the bentonite slurry:
≤

5%
The quality of the bentonite will check 1 time per bore hole as before pouring into the
bore hole. The result of test will be as following the table
No Item Range of result
1 Density Less than 1.10g/ml
2 Viscosity 30-90s or less than 20 cP
3 pH 9.5-12
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3.8 Installation of rebar cage:
Before installing the rebar cage, Contractor will complete finishing the inspection of
the rebar cage.
After preliminary cleaning, Contractor will install the working stage on top of the
temporary casing.
The rebar cage will be lowered into the bore hole to design elevation by crane.
The lap of the main rebar will use the tie wire(steel, minimum 1.5mm diameter)
The rebar cage will be hanged by 3 pecies rebar.
3.9 Install the tremie pipe
After installing the rebar cage, the tremie pipe will be install at center of the bore
hole. The bottom of the tremie pipe will set about 20-30cm from the bottom of the bored
hole.
The length of the tremie pipe will use 3m, 2m and 1m for adjusting pipe,and will be
combined from 1m,2m,3m parts for convernience adjust the length of tremie.
3.10 Air lifting cleaning of bored hole:
After installing the tremie pipe, Contractor will check the depth of bored hole. In case
the bored hole is still clean, it will start the preparation of concreting work. In case it has
sediment, the bored hole will be cleaned by air lifting method. The air lifting method will
use the tremie pipe and D90mm pressed-air pipe. The air lifting method will be continue up
to cleaning of sediment.
3.11 Concreting work:
The concreting work will use the tremie pipe. It will insert sponge into the tremie

pipe avoid to segregation
The every mixer truck will check the concrete slump before unloading the concrete.
Slump of any trucks is less than requirement will be rejected.
The tremie pipe will keep to embed in the concrete at least 2m.
Contractor will measure the top of concrete level at every mixer truck
The top of concrete will be cast above the cut off level to at least 1.5m
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