1 WORKING SEQUENCY ON DETAIL

1.1 Safety education and training

Before construction, all staff of CDM Sub-Contractor who working in this project shall be trained following client's HSE requirement.

1.2 Site preparation

In this step, all necessary temporary work must be done to prepare for mass CDM drilling construction, such as:

• Temporary road for cement truck supply, equipment mobilization...

• Leveling

• Site office

• Temporary hostel

• Water and electricity distribution point for construction.

• Temporary storage.

Check the pictures below for detail

1.3 Massive CDM drilling

The construction site shall be divided into 3 parts which are Section A, Section B and Section C, totally 10 drilling rigs shall serve in the area and appropriate moving route shall be designed to assure the quality of the overlap parts between CDM piles. Check the drawing below for details.

2 COLUMN MAKING METHOD AND PROCEDURE

2.1 Drilling sequence:

2.1.1 Installation of a base machine

In the case of movement of a base machine, it fixes so that it may cover with a griddle

and safety can be maintained according to a working condition if needed.

2.1.2 Checking equipments

Following ITP form.

2.1.3 Perpendicular check and alignment

Base on the benchmarks were hand over by GEDI, CDM sub-contractor will use the total station machine and measure for locating pile setting out. The centre of pile is marked with a steel rod etc. On the occasion of digging, the inclineometer is use to check vertical, driver shall always maintain vertical tolerance under allowance.

2.1.4 Measurement of cement and water

Measurement water and cement to control by Sensor weight equipment at mixing plant

2.1.5 Mixing of cement and water

Cement and water are mixed in mixing tank. After mixing, cement slurry will be transfered to storage tank with constant stir to avoid settlement.

2.1.6 Drilling for improvement parts

The operator should watch the speed and depth meter during drilling and predetermine the depth so as to control drilling speed. In addition, drilling speed and depth is recorded and printout for each column.

2.1.7 Process of cement slurry injecting

Cement slurry shall be injected from a drilling rig to column by pump.

2.1.8 Rod raising

Within 1.0m at the bottom of column, repeating drilling sequence will be performed. Operator shall watch speed and seismograph, control the raising speed till the column is completed.

2.1.9 Others

It is necessary to remove all obstacles if any. Moreover, depending on a foundation situation, digging speed and the amount of slurry injections per minute may be changed.

Pictures below show the CDM pile production procedure

2.2 Construction cycle of soil cement column:

- Standard speed of digging, raising

①Base machine movement and Column centre setting

②Dry drilling (no slurry)

③Digging progress, injection and churning

④Repetition churning (end part)

⑤Raising churning (not injection)

⑥ Digging rotations speed Nd = 16.0 ~ 48.0 rpm/min

⑦ Raising rotations speed Nu = 16.0 ~ 48.0 rpm/min

⑧ Digging speed Vd = 0.5 ~ 1.5 m/min

⑨ Raising speed Vu = 1.0 ~ 3.0 m/min

Progress above is digging progress normal. Drilling method may be adjusted in according with the actual construction situation.

Example of calculation:

T: number of blade rotation

∑M: total number of mixing blades : 4 x 2 = 8

Nd = 40 rpm/min

Nu = 40 rpm/min

Vd = 1.0m/min

Vu = 2.0m/min

T = ∑M x {(Nd/Vd)+(Nu/Vu)} = 8 x {(40/1.0)+(40/2.0)} = 480 times/m

3 Quality Assurance And Quality Control

3.1 Equipment check:

All equipment will be checked, tested run and calibration before mass construction. Daily equipment test will be done daily, before start working.Contents should be obeyed:

3.2 Position and Column center marking:

Using Total Station Equipment to locate center of column, marking the center position by a steel rods.

Column coordination check and acceptance following ITP form.

3.3 Inspection and recording during construction

During the construction stage, we shall submit the Column quality monitoring reports, on which all the column making detail progress recorded .The control of the mixing process will be computerized to assure the best quality of mixture. After the placement of each column, one printout result will be generated from the computer showing the column number, time, depth of the column, content of cement slurry used in the mixing process and the number of rotation. The process will be recorded and submitted .

The example of a record paper

3.3.1 Verticality check

Check the verticality of the drilling machine by the Inclinometer Sensor System. Surveyor would calibrate verticality of rig twice a month.

The verticality will be managed by pile drive operator as well during drilling (All instruments displayed in the cabin of machine)

- Allowable deviation:

Allowable deviation shall be as follows :

Vertical deviation of column shall not be more than 1/100.

Position of each column and spacing between columns shall not be deviated more than 100mm in any direction.

The diameter of column shall not be less than the specified value (1000mm).

Elevation of pile head and tip shall not be deviated more than 100mm.

Average unconfined compressive strength shall not be less than 1.0 MPa.

3.3.2 Core boring and Compaction test

The Tenocolumns shall be checked in term of strength by Core boring and compression test.

Test will take 03 samples x 3 locations on pile in once per 200 piles. One professional Lab will be responsibility for this test.

- Coring machine

- Coring

Coring by double core tube method.

Samples after coring

Base on coring samples, the Lab will determine the elevation of pile head & tip and the integrity of CDM pile. All results will be recorded on test report.

- Unconfined compression test

Standard for unconfined compression test ASTM D2166-85 or JIS A 1218:1998 will be applied.

Unconfined compressive tests of the cored sample on site will be made after 28 days.

Core method

Position of samples on pile: top, middle and bottom of pile.

Samples dimension: height = 10cm, diameter = 5cm.

Samples store: in accordance with specification.

Strength of test should be follow up to below formula:

Fi ≥Fc , Fc = compression strength as designed value (1.0MPa)

F ≥ 0.85Fc , Fi: average value of strength testing of three samples (1 set)

F: strength of testing sample

3.3.3 Material control

a. Cement:

The used cement type is Holcim Stable Soil. Average quantity cement by supplier for project is 400 tons/day.

Cement supplied schedule allway will be correct quatity for site work and have an exactly providing plan.

Material quality have to be ensured in progress saving at store or transporting.

Transportation plan: Base on the location of GEDI’s cement store at site, tanker vehicle (type 30 tons) will be used. Onsite, tanker vehicle will transport following temporary road to each mixing plant. At mixing plant, cement will be stored in silos, each mixing plant have 02 silos (30 - 35 tons/ silo). All cement silos are equiped with pump to pump cement to mixing tank. Cement silos at site will be in good condition and have not leakage water.

Cement will be taken sample for quality testing in every 500 tons in accordance with TCVN 2316-2007.

Quantity control of cement:

Cement quantity will be controlled by scale system before pumped to cement silos.

Cement received will be record and report daily.

Compare between received quantity and cement injected shall be weekly checked and reported.

b. Water:

Clean water shall be supplied by GEDI and PVC pipe shall be used to supply water to mixing plant.

Water demand for construction work is 200 m³/h, which shall be met during work.

Dirty water with organics which may harm the pile quality shall be forbidden.

Water samples shall be taken for quality testing one time before mass construction in accordance with TCXDVN 302 : 2004.

c. Electricity for construction:

Drilling machines using diesel electric generator for auger motor.

Electricity for mixing tank, cement silo, pump machine, light system etc. shall be three phases 220V electricity of government (supplied by GEDI).

3.3.4 Water/ cement ratio

Cement: Holcim Stable Soil

Water: clean water.

Water/ cement ratio: 0.8 (subject to change after trial piles)

Cement ratio management follow up design and control by computer from mixing tank.

Specific gravity of cement slurry: 1.57kg/l (with water/cement ratio : 0.8)

Cement dosage: 230 kg/m3 or 180.6 kg/m.

Cement slurry volume for 1m: 206.4 l/m

Management Items: