GRBCC MS CIPCP a2 EN

This method statement contains Bored Pile Work drilling ~ reinforcement ~ casting concrete, PileHead Treatment and Grouting Sonic Tube, except the description of Sonic Test and Static Lo

1 General - 3

2 Quantity of Work - 3

3 Schedule of Work - 4

4 Site Organization - 4

5 Equipment and Workforce - 5

5.1 Bored Pile Work - 5

5.2 Grouting Sonic Tube - 6

5.3 Pile Head Treatment - 7

6 Materials - 8

6.1 Bored Pile Work - 8

6.2 Grouting Sonic Tube - 8

7 Construction Procedure 7.1 Bored Pile Work - 9

7.2 Grouting Sonic Tube - 20

7.3 Pile Head Treatment - 21

8 Quality Control - 22

9 Safety Control - 23

10 Environmental Control - 24

Appendixes

1 Construction Schedule -03 pages (A3 size)

2 Drawing of Hanging Bar - 01 page (A3 size)

3 Inspection and Testing Plan -03 pages (A4 size)

4 Check Sheet -30 pages (A4 size)

(Total 67 pages)

1 General

This method statement describes the construction procedure and quality control aspects of Place Concrete Pile construction in accordance with General Specifications section 06210

Cast-In-Proposal of sub-contractor will be submitted separately

The working drawing will be submitted after receipt of final design of Bored Pile such as length andlocation of pile

This method statement contains Bored Pile Work (drilling ~ reinforcement ~ casting concrete), PileHead Treatment and Grouting Sonic Tube, except the description of Sonic Test and Static Load Test

4 Site Organization

Site Organization Chart for Cast-In-Place Concrete Pile construction is as followings

5 Equipment and Workforce

5.1 Bored Pile Work

The list of equipment and worker for a typical working party for Bored Pile Work is shown below.Plural working parties will be provided to work at several locations simultaneously Detail ofequipment and workers should be submitted separately in order to check and approve by theEngineer before commencement of bored piling work And they shall be inspected by the Engineer

in accordance with Guide Form No BBMMNL.(Apendix -4)

Table 5.1 List of Equipment for Bored Pile Work

1 Drilling Machine(Base Machine) Crawler TypeMax Drilling Depth 61 m

Max dia 2.0m 1 no. Equivalent Bauer – BG25

2 Service Crane 40t class crawlerBoom Length 31 m 1 no

3 Hydraulic Excavator 0.4~0.7 m3 Excavator 1 no

5 Mud Screen 4-6 inches 7.5 KW 1 no for cleaning bentonite liquid

11 Air Compressor pressure 7kgf/cm2 1 no

12 Tremie pipe 10 inches - total 57m 1 set Depend on bored pile length

15 Steel Casing Pipe D=1100mm 2 each Length =6.0m

20 Concrete Hopper 1.0 m3 1 no if required for casting concrete depending on the site condition

21 Dump Truck 10~15t 3 nos to transport excavated soil

23 Bentonite Liquid Sampler 1 L/S for testing bentonite

25 Funnel Viscosity Meter 1 no for testing bentonite

Table 5.2 List of Worker for Bored Pile Work

2 Skilled Worker (1) for drilling, casting, cleaning hole 10

3 Skilled Worker (2) for fabrication and installation re-bar cage 5

5.2 Grouting Sonic Tube

The list of equipment and worker for Grouting Sonic Tube is shown below The detail of equipmentand worker shall be inspected by the Engineer in accordance with Guide Form No BBMMNL

Table 5.3 List of Equipment for Grouting Sonic Tube

2 Grout Pump 5 mpressure 5kg/cm3/hour 2 1 with 1” hose

Table 5.6 List of Worker for Grouting Sonic Tube

5.3 Pile Head Treatment

The list of equipment and worker for Pile Head Treatment is shown below The detail of equipmentand worker shall be inspected by the Engineer in accordance with Guide Form No BBMMNL

Table 5.3 List of Equipment for Pile Head Treatment

Table 5.4 List of Worker for Pile Head Treatment

2 Skilled Worker for demolish concrete 10

6 Materials

6.1 Bored Pile Work

List of required material is shown below

Table 6.1 List of Material for Bored Pile Work

Reinforcing Bar CB400-V,

CB240T

Fy(min)=400Mpa,Fy(min)=240Mpa in accordance with 06400(item 2.2.1)Concrete Class Y 30Mpa in accordance with 06100(Item 2.2.2)

Proposal of Bentonite material and Steel Pipe (Sonic Tube) should be submitted separately asprocedure for material approval The bentonite suspension shall satisfy the testing criteria asspecified in General Specifications 06210, item 2.2.5 Actual ratio of bentonite mix shall besubject to final approval of the Engineer

Material stocked on site shall be kept off the ground and covered to protect from rain and dirty

6.2 Grouting Sonic Tube

List of required material is shown below

Table 6.2 List of Material for Grouting Sonic Tube

(Remarks)

For grouting, cement milk (W/C= 100%) will be used Mix proportion is as below

Cement 760kg, Water 760kg (for grout 1.0m3)

Trial mix and compressive strength test for grouting will be carried out with above proportion underinspection of the Engineer And report will be submitted to the Engineer for approval beforecommencement of grouting work

7 Construction Procedure

7.1 Bored Pile Work

7.1.1 Work Flow of Bored Pile Work

7.1.2 Description of Work Sequence for Bored Pile Work

(*) Trial pile and static load test

According to General Specification section 06210, Item 3.6.4 and 3.6.9 Trial pile is separate fromthe bridge foundation, and is installed and tested prior to commencement of construction ofcontract piles Sequence for construction of trial pile is the same as Sequence for construction ofcontract piles described in this document Location of trial pile shall be proposed by theContractor and approved by the Engineer Method Statement for static load test of trial pile shall

be made and submitted separately

(1)

Mobilization and Preparation

Prior to commencing the drilling work, all equipment and worker shall be inspected according toGuide Form No BBMMNL with attendance of the Engineer

Any obstacles at the surface or the sub-surface of the ground are to be taken out by Excavator orother drilling equipment

Underground water level shall be measured before piling work by temporary well or drilled hole,which shall be made temporary with adequate depth to investigate underground water If

necessary, embankment shall be applied to keep that the execution area of piling works is more

than 2.0m above underground water level.

( 2 ) Setting O u t Pile Center

The transverse line setting out:

Positioning shall be based on design drawings for pile layout plan and shall not deviate morethan 80mm from the theoretically correct position shown on the drawing (According to GeneralSpecification, Section 6210 item 3.7)

Reference marks wil be established for determination of pile centerline during construction.The center of pile shall be surveyed and inspected with the Engineer’s surveyor for each pile

before drilling.

( 3 ) Setting Drilling Machine

Base machine shall be set upon the pile

center horizontally and vertically Offset

points for pile center shall be made at

least in two directions from inspected

marking of pile center The centering of

the machine shall be confirmed by the

tip of Kelly bar or bucket Horizontal

setting of machine and verticality of

Kelly bar shall be checked by water

level gauge or plum It is necessary to

put steel plate on working ground for the

foundation bed of drilling machine to

keep stability of machine and bored

hole

( 4 ) Pre-drilling and Setting Casing Pipe

 To protect the top of hole, a casing pipe shall be installed after pre-drilling with depth less thanthe length of casing pipe from 0.5m to 1.0m depending on soil condition

 The purpose to use casing pipe is to protect the strata below G.L from collapse caused byheavy weight of various heavy machines and also to protect the hole from mud water on theground Inner diameter of casing pipe shall be 10~20 cm larger than designed pile diameter.Length of casing pipe shall be from 6.0m to 10m depending on soil condition Casing pipeshall be inspected with attendance of the Engineer before installation

 Top of casing pipe should be higher than working ground level at least 50cm and twosupporters at top of casing pipe should be placed firmly on steel plates

 The center of casing pipe shall be confirmed from offset marking of pile center and totalstation from construction point of survey, and its verticality shall be checked by water levelgauge After installation of casing pipe, location of center of casing pipe and verticality shall

be inspected by the Engineer’s surveyor Maximum tolerance of gradient of casing pipe is 1%

( 5 ) Drilling (up to designed depth)

Preparation of Bentonite Liquid

Bentonite shall be mixed with water by mixing machine and in proper proportion (about 80kg/m3 water) Bentonite shall be well-mixing within 10-15minutes/m3 of the mixing inorder not to be clotted and then discharging to the tank

60-The specification of bentonite shall be always checked (density, viscosity, sand content, PHvalue)

The supplying pipe and discharging pipe of bentonite shall be always checked throughout thepiling work in order to ensure that supplying of bentonite shall always maintain in soundcondition, During piling work bentonite shall be adjusted properly depending on different strata

in order to maintain the stability of the bore-wall

Specification of Bentonite shall be as follows:

Drilling 1st

Cleaning

2ndCleaning(beforecasting)

1 Density ≤1.10 gm/ml Mud density

4 Shear strength 1.4-10 N/m2 Shearometer o

measure pipe

boredhole)

(Bottom

of boredhole)

(Bottom

of boredhole)

The facility for circulation of bentonite liquid shall be set up as below.

Pit for Waste Liquid

Pump

Pump

Sedimentation Tank No.2 Sedimentation Tank No.1

Used Bentinite Liquid from Bored Hole

Pump

Tank for Stock Clear Bentonite Liquid Sedimentation Tank No.4 Sedimentation Tank No.3 Water Tank

Bentonite Mixer

Clean Bentinite Liquid

to Bored Hole

Syclone Mud Screen

Circulation tank for bentonite liquid shall be checked timely during piling work and precipitatedmaterial in tank such as sand or mud shall be removed adequately

(5)

Drilling Work

Drilling work nearly up to the toe of the casing pipe will be done without bentonite liquid Afterinstallation of bentonite liquid into the bored hole, drilling work will be continued and the toplevel of stabilization liquid shall be maintained 2.0m higher than under ground water level.When the screw auger is lifted up, the screw auger is to be rotated reversibly to release drilledsoil and to be lifted up slowly to protect the hole from collapse And the screw auger shall beput down slowly also to protect the hole from collapse The control of verticality during drillingwork shall be made by plumb with string or theodolites from two directions in 90 degree.During the drilling works, soil stratum shall be monitored and recorded carefully to check actualsoil condition under inspection of the Engineer, and the bentonite liquid shall be tested at least 2times a day or interval 4 to 6 hours under inspection of the Engineer

When drilling into rock layer, using screw auger sticked hard alloy

Confirmation of Bearing Layer

The confirmation of the bearing layer shall be made by the visual check of excavated soil takenout from the bottom of bored hole under inspection of the Engineer, which is assumed byreference of geological survey report

The drilling depth shall conform to the approved working drawings The bottom E.L of boredhole shall be measured from top of casing pipe by the measuring tape with weight Theinspection of drilling depth shall be taken with attendance of the Engineer

If actual depth of bearing layer is not corresponded to geological survey result and design ofpile, countermeasure for drilling depth shall follow to the Engineer’s instruction, such as extendexcavation depth and pile length

( 6 ) Waiting for Sedimentation ~ 1 st Cleaning Bottom of Hole by Bucket

After completion of excavation of bored hole, it shall wait for sedimentation of slime for 2~3hours During waiting for sedimentation, head of bentonite liquid in casing pipe shall bemaintained to keep more than 2.0m above under ground water level Finally, the sedimentation

of slime at the bottom of the bored hole shall be scraped and removed by a cleaning bucket.After clearing bottom, depth of bored hole shall be measured again under inspection of theEngineer

( 7 ) Fabrication of Re-bar Cage

Re-bar cage shall be fabricated in accordance with approved working drawing

The main rebar should be welded with temporary reinforcing ring bar to keep shape andstability of cage Design hoop bar shall be tied with main re-bar with iron wire

Sonic tube should be fixed by welding with temporary reinforcing ring bar at some location Atthe bottom of rebar cage, sonic tube should be fixed by welding into steel plate, and steel plate

is fixed by welding with rebar net at bottom of rebar cage To ensure bottom of sonic tube, itwill be permanently sealed and top of sonic tube shall be provided with welding steel plate toprevent the ingress of any undesirable materials Top of Sonic tube shall be higher thantemporary casing at least 30mm

Top of Sonic tube shall be extended above cut off level of pile adequately in order to carry outSonic Test as soon as possible (7days after casting concrete) without structure excavation andpile head treatment It will be shown on working drawings (Sonic Test shall be carried outbefore structure excavation and pile head treatment to avoid unsuccessfully testing due todamage of sonic tube or obstruction in sonic tube.) The sonic tube section above cut off level ofpile should be kept by temporary rebar frame in order to keep the distance between sonic tubeswhich shall not be changed during installation of re-bar cage and placing concrete

After fabrication, all of cage shall be inspected by the Engineer

Fabrication of re-bar cage should be carried out separately from drilling work And beforecommencement of drilling, fabrication of re-bar for that pile shall be completed and inspected

by the Engineer

During fabrication, re-bar and fabricated cage shall be kept off the ground Stocked re-bar andcage also shall be kept minimum 20cm off the ground and covered by sheet to protect from rain

and dirty.

( 8 ) Installation of Re-bar Cage

Re-bar cage shall be installed one by one in bored hole

by service crane

Connection of re-bar cages shall be made by welding

main re-bars with 30~50cm combined with tightening

by iron wires to prevent fall down re-bar cage during

installation The length of splicing re-bar shall conform

to specified length on approved working drawing And

hoop bars at splicing location shall be installed correctly

after splicing re-bar cage At the same time, sonic tube

also shall be jointed together by welding with covered

tube High attention not to damage re-bar cage during

lifting bar cage by crane and not to fall down of

re-bar cage during splicing re-re-bar cage shall be paid

During installation of re-bar cage, splicing length of

main bar and installed hoop bar shall be inspected by

the Engineer Verticality of re-bar cage during

installation should be controlled by plumbs That is

located at least in two directions

After completion of splicing all rebar cages, the top E.L

of casing shall be surveyed with attendance of the

Engineer And the length of hanging bar for re-bar cage

from top of casing pipe shall be calculated based on

designed E.L of re-bar cage and surveyed E.L of

casing pipe Then, hanging bar shall be fabricated with

correct length and shape and welded with main re-bar of

top re-bar cage After installation of hanging bar, re-bar

cage shall be lowered slowly down to designed

elevation, and it shall be suspended from the top of steel

casing pipe by hanging bar Detail of hanging bar has

been shown on attached drawing (appendix 2)

Re-bar Cage