Preliminary Method Statement

Luanda Oil Service Base Expansion Contract for Tender Submission

Quay Wall between Heavy Lift Dock and TCT Area Method Statement

Preliminary Method Statement for

Quay Wall between Heavy Lift Dock and TCT Area

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Table of Contents

1 General.............................................................................................................................3

1.1 Site Location............................................................................................................3

1.2 Scope of Work..........................................................................................................4

1.3 General Construction Flowchart..............................................................................5

2 Temporary Facilities.......................................................................................................7

3 Construction...................................................................................................................7

3.1 Dredging...................................................................................................................8

3.2 Rubble Bedding for Foundation Trench.................................................................10

3.3 Precast Counterfort units.......................................................................................15

3.4 Installation of Counterfort Units..............................................................................19

3.5 Backfilling Sand and Vibro-compaction.................................................................23

3.6 Demolition Works...................................................................................................24

3.7 Cast In-situ Capping Beam....................................................................................25

3.8 Drainage Culvert....................................................................................................28

3.9 Construction of Apron including Trench.................................................................28

3.10 Installation of Auxiliary Facilities............................................................................32

3.11 Placement of Anti-scour Protection........................................................................33

3.12 Fender Replacement and Concrete Repairs.........................................................35

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1 General

It is intended to construct a new quay wall at the Port of Luanda, Angola, currently

known as the Luanda Oil Service Centre. The project comprises the construction of

442.9m long quay wall identified on the drawings referred to in the Employer’s

Requirements, with cope at 3.35 m CD, having a design depth of -12.5m CD

including foundation works and anti-scour protection below -12.5m CD level, tying-

in with the existing quay walls and complete with navigation, berthing and mooring

equipment and provision of spare berthing equipment.

1.1 Site Location

The Project Site is located at the Port of Luanda, Angola, currently known as the

Luanda Oil Service Centre, as indicated in the following figures:

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Site Location

1.2 Scope of Work

The scope of the work required includes the following:

A. Construction of a new quay wall extension comprising:

A new 442.9m long quay wall identified on the drawings referred to in the

Employer’s Requirements, with cope at 3.35 m CD, having a design depth of -

12.5m CD including foundation works and anti-scour protection below -12.5m

CD level, tying-in with the existing quay walls and complete with navigation,

berthing and mooring equipment and provision of spare berthing equipment.

Dredging to lower the seabed in front of the quay wall to –12.5m CD and

disposal of spoil to a location to be agreed with the Employer within Luanda

Bay.

Removal of an existing pipe spooling jetty, piles along shoreline, small craft

quay and disposal of materials off site.

Such temporary works as may be required to maintain the integrity of the

existing quay walls, edge of TCT container yard, outfall channels and any other

structures earthworks during construction for the new quay wall.

Backfilling behind the quay wall using dredged sand material provided by the

Contractor. The Contractor shall be responsible to determine where sand

material can be obtained for the backfilling and shall obtain the necessary

approvals from the relevant authorities for the removal of sand. Backfilling shall

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follow the removal of slope protection material including piles and concrete

blocks along the shoreline close to the Contractor`s construction yard. The

slope protection rock material may be used in the works if suitable or elsewhere

at a price agreed with Sonils. This will be deducted from the Contractors

payment claims.

A paved quay apron 30 m wide behind the new quay wall and the ends of the

existing walls.

Pipe trenches in the quay wall and apron.

Surface water drainage installations including extensions of 3no. existing outfall

culverts and incorporation of 2no. into the new quay wall extension.

B. Supply and installation of replacement fenders and repair of concrete along the

existing quay wall.

1.3 General Construction Flowchart

To ensure the achievement of schedule of the project, the construction of each

phase/section should be started as early as possible. As the dredging of foundation

trench gets started, the construction of precast concrete counterforts should be

initially performed, so as to proceed the following construction as soon as possible.

The general construction flowchart of the Project is shown as follows:

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Construction Flowchart

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Luanda Oil Service Base Expansion Contract for Tender SubmissionQuay Wall between Heavy Lift Dock and TCT Area

Method Statement

2 Temporary Facilities

Referring to the following figure, the existing temporary facilities, including the

living camp, precast yard, batching plant, etc., will be reused after decoration

and repairs. Site office may be established within the living camp or by precast

yard site whose area to be provided by the Employer.

General Layout of Temporary Facilities

3 Construction

After the contract has been awarded, the manpower mobilization will be started

immediately. Most of the manpower will be mobilized, so that the Project can be

started as soon as possible. Normally, the senior staffs will be initially mobilized

to the site within four week to start the preparation works. Part of skilled workers

will be mobilized initially to start the construction of temporary facilities within

three month. Other skilled labors and semi labors will be mobilized subsequently

basing on the construction schedule. Part of skilled workers, semi labors and

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Method Statement

unskilled labors will be recruited locally in Luanda, Angola.

The mobilization of the Equipment, such as grab dredger, flat top barge, floating

crane, etc., will also be commenced early. After obtaining the construction

permission and consents, the dredging construction will be executed

immediately.

3.1 Dredging

3.1.1 General

The works comprises the execution of dredging works required for foundation

trench and leveling of the berth pocket in front of the new quay wall to -12.5 m

CD as indicated on the drawings in Employer’s Requirements.

3.1.2 Dredging Method

For this terminal, the grab dredger will be allocated to the dredging works with

the assistance of the split hopper barge. All dredging work will be carried out

vertically in layers and horizontally bays. The sketch of dredging construction by

grab dredger is shown as below:

Grab

Dredger

Hopper

Barge Grab DredgerWater Level

Original level

Design level

Section of DredgingPlan of Dredging

The Sketch of Dredging

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Method Statement

Dredging by Grab Dredger

The procedure for dredging construction is shown as below:

The dredger will be positioned by GPS system. During the dredging, the level of

dredging will be measured by lead. One hydrographic measuring station will be

also set on the existing quay.

The dredging sample will be checked and compared with borehole data in time

when it is carried out to each layer. The width and depth of the dredging area will

be controlled in a tolerance of Employer’s Requirement. If the sample is different

with the design, it should be reported to the Employer to make further decision.

Significant data and information of the dredging will be recorded.

The dredging works will be monitored by regular hydrographic progress survey in

order to verify that works are being executed in accordance with the scope of

design. The survey will be carried by echo sounder and GPS positioning device.

The post-dredging survey must be carried out immediately after the dredging of

the bay is finished.

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Method Statement

3.1.3 Construction Sequence and Schedule

The dredging sequence will be executed from dredging of foundation trench to

dredging of berth pocket in front of quay wall. Considering the site condition,

disposal distance and vessels’ maintenance, about 1,200m3 materials per day

will be executed by grab dredger.

3.1.4 Disposal of Dredging Materials

The disposal areas are not yet identified exactly but it is assumed that dredged

materials will be dumped offshore to a location to be agreed with the Employer

within Luanda Bay.

3.1.5 Dredging Equipment

Major intended equipment resources for dredging are listed as below:

S/N Description Qty. Remark

1 Grab Dredger, 13m3 1

2 Split Hopper Barge, 500m3 2

3 Tug Boat, 1000Hp 1

4 Traffic Boat 1

5 GPS Positioning Device 1

6 Echo Sounder 1

3.2 Rubble Bedding for Foundation Trench

3.2.1 Rockfilling

The sketch of rockfilling for foundation trench is shown as follows and the

rockfilling quantity is about 55,000m³ .The stone will be supplied from the land

and transported to the temporary quay. The excavator will be used to load the

stone onto the 15m3 hoppers. When hoppers are fully loaded, they will be

transported to the specified position for rockfilling. For accurate positioning for

hoppers, flat top barge will be used for positioning by GPS. The method of

plumbing will be adopted to control the rockfilling height accurately.

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Method Statement

Sketch of Rockfilling for Foundation Trench

Before the rockfilling starts, the foundation trench, which has been accepted but

is not yet covered with rockfilling, shall be surveyed again. If the thickness of

back silting is above specified profile, it shall be reported to the site Engineer,

and the work for clearance of silt shall be organized.

Trial rockfilling shall be performed prior to determine the location of the hopper

and thickness of stone dumped at a time. Through different trial rockfilling with

different loads of stone, the load for a certain rockfilling thickness can be

determined. Thereby, proper methods for loading and positioning can also be

acquired.

First, the hopper will be used for the coarse-rockfilling, and then the flat top

barge loaded with stone will be accurately positioned for supplementary

rockfilling. During the rockfilling process, frequent plumbing and mark aiming will

be performed to avoid under-rockfilling or over-rockfilling.

Settlement shall be taken into consideration for the rockfilling of foundation bed.

The preserved amount of settlement shall be determined by design requirement.

3.2.2 Ramming

One crawler crane 70t will be fixed on the flat top barge for foundation trench

compaction. The foundation trench shall be compacted by ramming in layers

according to thickness; and the thickness of the layer is not advisable to be

greater than 3m after compaction. Adjacent ramming rounds with half

overlapped with each other longitudinally and transversely will be adopted for

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Method Statement

compaction.

The rammer will be planned to use 5 t in weight with 1.0m diameter circular

bottom. When the buoyant force and resistance is not taken into account, the

impact energy of each ramming is not advisable to be less than 120KJ/m2. The

compact energy can be obtained when lifted height is up to 2.5m. The rammer

shall be lifted up to 3 m to achieve compact energy of 130kJ/m2 for each

ramming.

The ramming for rockfilling bed shall proceed from one point to another, with

adjacent ramming circles half overlapped with each other longitudinally and

transversely as shown in the sketch, and will be carried out in two rounds, with

the initial ramming followed by the recurrence, four times ramming at each point

for each round, and 8 times ramming in total for each point.

Sketch of Layout of Rammer’s Falling Points

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Method Statement

Sketch of Ramming for Trench

The foundation trench shall be divided into 2 sections, with 2 m overlapped

length, and 3m in thickness for each layer.

The plane of each rockfilling layer shall be checked before starting the ramming,

and leveling shall be executed if height difference between adjacent locations is

more than 0.3m.

Typical area, with 1m exceeding each side of counterfort and length of 10m,

shall be chose as the trial section.

The initial ramming and recurrence will be executed by the same means of

adjacent ramming rounds half overlapped with each other longitudinally and

transversely to prevent local heave of foundation bed or flaw of ramming. 1 m

exceeding front/back side line of the counterfort will be taken for rammed width.

The reserved settlement value will be adjusted according to the trial ramming

properly.

3.2.3 Leveling

The area of foundation trench to be leveled is about 6700m². When the rockfilling

for foundation trench is completed and accepted, the work of leveling will be

commenced at once.

The survey rod will be controlled by the total station for rails placement of the

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Method Statement

leveling work, while the survey rod will be controlled by the water level to obtain

the elevations. For the placement of rails, the control points shall be set on the

temporary survey station.

Please refer to the following sketch for leveling of foundation trech:

Sketch of Foundation Trench Leveling

One leveling barge and some divers will be involved for foundation leveling. The

amount of rubble stone and crushed stone shall be estimated beforehand

according to the as-built section of the rockfilling works, and the stone needed

shall be prepared.

Flat top barge will be served for leveling, which can be loaded with the stone for

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Method Statement

leveling. Crushed stone will be used at the last step for fine leveling. Via the

woven bag which will be raised and put down by manpower, the crushed stone

will be transited to the location controlled by the diver for leveling.

Divers will be employed to lay the steel rails underwater, and a leveler will be

equipped on the rails to level the crushed stone within reach. Surveyors shall

erect the total station at the survey station and direct the divers to place the steel

rails by observing the instruments. The divers shall place concrete blocks

underwater to support the steel rails. Elevation of the rails shall be controlled by

the water level and survey rod. When the steel rails are ready, two teams of

divers shall dive into water at the same time, and push the leveler forward along

the steel rails.

During the process for fine leveling, rubble stone shall be used to fill the uneven

position among rock blocks, while crushed stone shall be used to fill the uneven

position among rubble stone. The crushed stone is allowed to form a layer with

thickness less than 5cm. Only those crushed stone of 2~4cm shall be used. Via

the bamboo basket which will be raised and put down by manpower, the crushed

stone will be transferred to the position required through underwater wire

telephone communication between the diver and surveyor. The divers shall push

the leveler (such straight hard material as channel steel) along the rails to level

the stone. And the completion of leveling for a section of foundation bed shall be

followed by the operation for the next section.

Elevation and position of rails shall be rechecked at the time after the fine

leveling. If any deviation beyond allowable is found, the rails shall be adjusted.

Life buoys connected with concrete block through nylon rope shall be placed for

each corner of the leveled section of foundation bed. And those area completely

leveled shall be kept away from anchoring of vessels.

3.3 Precast Counterfort units

3.3.1 General

There are 53 units of counterfort (CF) to be precast in this project, with 51 units

of standard and 2 special. All of the CFs will be prefabricated at the precast yard,

with 9130m3 concrete involved. The precast sequence will in accordance with

the requirement of site installation.

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Method Statement

3.3.2 Existing Temporary Works

The existing temporary works, including precast yard, batching plant, etc., will

be used after decoration and repairs. The sketch layout of temporary works is

shown as followings:

Sketch of General Layout of Temporary Works

3.3.3 Construction Method

A. General arrangement

Two precast lines will be arranged for CF prefabrication. 8 CF units will be

completed every month. Ballonet method will be used for transporting the

precast unit.

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Method Statement

B. Bottom Formwork Preparation

For the convenience of ballonet loading out, 5 groups of I-Steels (32#) and one

group channel steel shall be placed transversally on the floor to form 5

interspaces, at the ends of the interspaces, built-up type steel formwork shall be

placed transversally to connect with the longitudinal I-bars. Thus the outline of

the bottom formwork can be formed. Sand shall then be filled into the 5

interspaces, which shall later be watered and compacted until the surface of

sand is the same level as that of the I-bars and channel steel. Afterwards, 20mm

thick wooden board and paper shall be placed onto the sand form the bottom

formwork. To transport the components, remove the transversal steel formwork

at the ends of the I-bars, clear away the sand in the interspaces, then insert the

ballonets into the interspaces, when the component is lifted by the ballonets filled

with air, the I-bars shall then be removed, and the component can be loaded out

to the temporary quay by revolving the ballonets in shift.

As there 2 special counterfort in this project, one set of the formworks should be

changed correspondingly. These special will be planed to be produced finally, so

that the formwork will not have to be changed for tow times.

C. Processing and Erecting of Rebar

After processing in the shed, the rebar shall be transported to the site by trucks

and then be erected on the bottom formwork. Auxiliary steel frame for rebar

erection between rib slab and the upright slab shall consist of 7 layers, each

layer 2.0m in height.

The auxiliary framework mentioned shall be welded into an integer by profile

steel and fixed with the bottom formwork. The erecting of rebar shall be kept

stable and fasten. In order to hang the vertical rebar of upright slab and rib slab,

movable profile steel and horizontal hanger rod shall be set up on top of the steel

framework. Vertical rebar shall be hanged onto the horizontal hanger rob

according to the design space, a certain numbers of horizontal rebar shall be

fastened on the top, middle and bottom of the vertical rebar to form a frame

structure, afterwards, from the upper to the down. The inner rebar shall be

erected first, then the outer horizontal rebar, and finally the rebar for bottom slab.

When the bar erection work is completed, concrete cover spacer shall be placed

on the surface of the rebar cage, outer formwork can be installed then.

Supported by the outer formwork, the rebar of the counterfort shall keep stable,

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Method Statement

afterwards, the frame for bar erection will be hoisted out, and the working

procedure for fixing and erection of rebar has been fully finished.

D. Side Formwork

CHEC has rich experience in precasting the same counterfort in the Quay Wall

and GRN project. The gantry crane 20t will be used for formwork installation/

removal, while the inner formwork shall be installed layer by layer, concrete

casting shall be performed continuously until it is completed, so that the

concreting can go on smoothly, and the quality of the counterfort units can be

well ensured.

Formwork for one side of bottom slab shall be installed as a whole according to

the setting-out location. Large formwork with a weight of 15t will be used as outer

formwork. Outside the steel plate surface, horizontal trusses shall be erected at

the height of 1.2m. The adjacent trusses at both ends of the upright wall of

counterfort will be connected into a whole to form a bearing grid. Bolts that can

be fastened at both ends will be equipped in each rib of the horizontal trusses of

the upright wall. Therefore, a bearing structure of multi-span continuous beam is

formed. The bolts that can be fastened at both ends shall then be connected with

the frame of inner formwork.

Both the counterfort rib slabs and the inner formwork of the upright wall consist

of 7 layers with 2m layer height. Position for erecting of formwork shall be set out

on the bottom formwork, and the marks shall be made at the place where

supporting concrete block need to place. Place concrete column block at the

right place, where steel formwork for bottom slab shall be installed. The inner

formwork for each layer shall be hanged to the corresponding steel truss. And

removable formwork chamfered for the convenience of formwork removal shall

be installed at the corner. Bolts shall be installed between inner formwork and

outer formwork. The support column for inner formwork of each layer shall be

connected by bolts end to end. And sealing strip shall be used for joints between

formwork. A platform with bevel will be erected with the inner formwork to

facilitate the concrete casting. The weight for each section of inner formwork and

the support frame is about 10t, and it will be hoisted and installed by gantry

crane.

As there are 2 special counterfort is this project, one set of the formworks should

be changed correspondingly. These special ones will be produced last, so that

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Method Statement

the formwork won’t have to be changed two times.

E. Concrete Casting

With reference to the design of formwork, the outer formwork installation shall be

completed at the beginning for concrete casting. The inner formwork between

two ribs shall be divided into 7 layers. They shall be assembled section after

section, and then be installed layer by layer along with the concrete casting

process.

When the installation of formwork is completed and concreting has been

approved by the Engineer, the concrete casting may be commenced at once.

The gantry crane with the concrete bucket or concrete pump truck will be used

for the casting operation. Concrete will be supplied by the batching plant on site,

and be delivered to site by concrete truck. Later, the concrete will be released

into the concrete bucket, hoisted to the formwork by the gantry crane or directly

cast by pump truck. Labors shall then be employed to release the concrete into

the formwork and compact it by the internal vibrator.

The bottom slab and the first layer of 2m high wall and rib shall be cast first, and

then the inner formwork for each layer shall be installed along with the increasing

concrete. Each layer for concrete casting shall be 2m in height. About 2 hours

(less time for the smaller upper section) will be taken for the casting of each

layer. About 1 hour for formwork installation of one layer. So 3 hours will be taken

on average for completion of one layer. Taken other factors into consideration,

the 7 layers including the bottom slab, can be completed within 21 hours.

Meanwhile retarder shall be added into the concrete to ensure the initial setting

time prolonged to 4.5-5 hours.

In the case of heavy rain during casting concrete, the casting can make a pause

temporary, and be better to cover the concrete with plastic sheet for a while. If

the casting cannot be stopped or resumed after pausing, the mix of the concrete

should be adjusted appropriately.

F. Curing

When the required strength of the concrete is obtained and approved by the

Engineer, side formwork can be removed. The concrete shall then be marked

and be cured continuously with fresh water. The water for concrete curing shall

comply with the design requirement. The unit shall be cured with water for 7

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Method Statement

days.

When the component reaches the 100% of the design strength, it can be moved

to the temporary quay by ballonets, and then be hoisted to the barge for

installation by barge crane.

3.4 Installation of Counterfort Units

3.4.1 General

There are 53 pieces counterfort (CF) units weigh about 432t for each. They will

be transported from the precast area to the temporary quay by ballonets, loaded

on flat top barge 1000t and installed by floating crane with maximal hoisting

capability of 800t.

3.4.2 Construction Method

Ballonet will be used to transport the CF from precast area to temporary quay for

installation. Structure of ballonet is shown as follows:

A ballonet consists of its body, head and nozzle, etc. Its auxiliary parts include

safety valve, pressure meter and pipe joints, referring to the following sketch:

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Method Statement

Sketch of Ballonet Structure

The ballonet to be used in this project is made up of 6 layers. The allowable

working pressure is 0.2MPa; and the extreme pressure is 0.5MPa. One piece of

φ1000mm*9m ballonet weighs about 250kg; and generally the mass of the air

charged can be omitted.

In order to ensure horizontal load for the CF at the beginning of lifting up the unit,

the ballonets shall be set regularly along the moving direction of the CF. As per

the level load principle:

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Method Statement

CF Transported by Ballonet

Leveling for foundation trench rockfill must be inspected and accepted before

installation. The CF units will be hoisted and loaded on barge in sequence after

the concrete compressive strength of the units reach the designed strength. The

CF units will be hoisted about 50cm above the ground at first, and it will be lifted

up again when the floating crane becomes steady. The barycenter lines of the

CF unit and 2000t barge must be matched together when loading the unit on the

barge in order to avoid inclination of the barge caused by imbalanced load. The

plan for CF units loading on barge is shown as below:

Sketch of CF units Loading

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Method Statement

The floating crane and flat top barge will be moved to the Quay site with the help

of tug boat. The bow direction of floating crane shall be normal to the cope line of

the quay, and two front anchors will be connected with ground anchors buried

onshore or bollard.

Survey stations shall be prepared before installation. The survey stations should

be ensured observation without obstruction during installation, longitudinal

survey station and GPS shall be prepared separately for controlling the

positioning.

The installation sequence will commence from the Heavy Lift Dock to existing

GRN Quay. Timber will be prepared to control joints width in advance.

The positioning for floating crane and survey controlling are shown in the

sketches.

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Method Statement

Sketch of CF units Installation

The CF unit can be put on the foundation trench when the positioning is

satisfied, and divers will check width of joint and staggering between neighboring

units separately. The shackles can be released and removed when the checked

items are qualified.

Observation points for settlement and displacement can be set after the

installation, and they will be surveyed regularly or irregularly according to the

requirement.

3.5 Backfilling Sand and Vibro-compaction

3.5.1 Backfilling Sand

Backfilling sand will be executed after the completion of geotextile filter layer.

Dredged sand will be used as backfill material. The quantity of the backfill ing

sand behind the quay wall is about 590,000m3.

To prevent the foundation being silted, the sand will be backfilled when 30 CF

units (about 255m) are installed. And the method of backfilling is hydraulic

backfilling. The bathymetric survey should be carried out by GPS echo sounder

or hand-lead survey before backfilling, and then topographic map will be made to

calculate the quantity for hydraulic backfilling. Hydraulic backfilling shall be

executed by reclamation dredger and be assisted to fill by bulldozer, dumpers

and excavator. Meanwhile the settlement and displacement of CF units will be

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Method Statement

monitored by surveyor during backfilling. The diver will check the geotextile filter

layer to ensure its stability during construction. Backfilling will be executed with

the sequence of CF installation.

The outlet of the hydraulic backfilling pipe will be laid in the location which is

about 40m from the copy line. Dredged sand will be used as the material, and

backfilled sand will be transported, loaded and leveled by excavator and

bulldozer to the front, Manpower will be used for partially trimming.

The Level of the quay apron after backfilling between 3 and 30m from the cope

line is about +3.0m, so the level after vibroflotation is about +2.0m, which is

above water level and is convenient for the subsequence construction. And the

level of the remainder is about +3.5m which should comply with the Employer

requirement.

3.5.2 Vibro-compaction

The backfilled sand will be treated (vibro-compacted) which is between 3m and

30m from the cope line.

Vibro-flotation lifted by crawler crane will be allocated to carry out this

construction, referring to the following sketch:

Compaction by Vibro-flotation

3.6 Demolition Works

The existing pipe spooling jetty, piles along shoreline, slope protection material

and emergency small craft quay shall be demolished and removed from site,

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Method Statement

specified in Employer’s Requirements.

The hydraulic breaker and excavator will be mainly used for the demolition

works. If agreed with the Engineer, the piles may be cut off at sea bed level,

provided they do not interfere with the quay wall works.

Acceptance of demolition works will be granted following the acceptance of the

surface by the Engineer and receipt of all required documentation.

The disposal areas are not yet identified exactly but it is assumed that demolition

materials will be dumped offsite at a distance, in a legal manner and with the

approval of local Authorities.

Demolition by Hydraulic Breaker

3.7 Cast In-situ Capping Beam

There is 442.9m cast-in-situ capping beam for the quay wall, which is divided

into 26 segments. The design compressive strength of the concrete is 40 MPa,

and the quantity of concrete involved is about 2861m³. The standard section of

quay wall is shown as below:

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Method Statement

Typical Section of Quay

Take the entire segment divided in accordance with the design as a construction

unit (17m as a segment), concrete will be cast in place every other segment from

Heavy Lift Dock to GRN Quay, and concrete casting for each segment shall be

finished at a time. The flow chart of cast in-situ process is as follows:

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Method Statement

Flow Chart of Cast in-situ Process

Triangle bracket will be installed at first; and then 100*100mm timber and

plywood for bottom formwork. Side formwork structure shall be 8mm thick steel

plate integrated with enclosing purlins. Formwork includes outside part, inner

part, and end-sealing part. Side formwork will be installed after the rebar erection

is inspected and accepted by the Engineer.

Sketch of Triangle Bracket for Bottom Formwork

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Method Statement

Side formwork will be installed by crawler crane, and the shape, straightness,

and dimension of the formwork shall conform to stipulations set forth in relevant

codes. The embedded bolts such as the rubber fender’s, bollard’s and ladder’s

should be fixed accurately and firmly at the same time.

The concrete will be produced by batching plant on site; it will be transported to

the quay wall site by mixer truck and will be cast by concrete pump.

Internal vibrator will be used for compacting concrete. Vibration quality shall be

ensured during casting, defects as honeycomb on concrete surface and air voids

should be avoided.

Finishing shall be performed with trowel when top elevation reaches, and screed

by manpower shall be used for leveling before initial setting of concrete.

When concrete compressive strength reaches 10N/mm2, side formwork can be

removed according to BS 8110 part 1. Side formwork will be removed by labors

with the help of crane. Attentions to safety and integrality of formwork should be

paid during the removal of formwork, don not prize and hammer here and there

so as to avoid deformation of formwork. Bottom formwork will be removed at last

when compressive strength conforms to relevant stipulation. The structure shall

be covered immediately and cured with fresh water or by applying curing agent,

and moist curing period shall not be less than 7 days.

3.8 Drainage Culvert

Surface water drainage installations, including extensions of 3 no. existing outfall

culverts and incorporation of 2 no. into the new quay wall extension, will be cast

on site. The concrete will be provided by the batching plant.

3.9 Construction of Apron including Trench

3.9.1 General

The quay has an apron of 30m wide. The section covers capping beam and

concrete pavement (service trench). As for the 25.1m wide pavement, it consists

of a 200mm thick graded crushed rock sub-base, a 250 thick lean concrete C15

base course and a 430mm thick reinforced concrete C40 surface course. The

total thickness is 880mm, and the section of apron is as follows:

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Method Statement

3.9.2 Service Trench

Service trenches are situated longitudinally and transversely in the quay. The

dimension of the trench situated transversely is 1.87m in height and 2.2m in

width, it is a single box with two cells. The dimension of the longitudinal trench is

1.65~1.87m in height and 1.9m in width, which is a single box with one cell.

Cover slabs will be precast and installed for the trenches. The compressive

strength of the concrete for the trench is 40MPa. There is about 1684m3

concrete involved in service trenches.

The cover slab prefabrication is prior to the principle part of trench construction.

The trench construction procedure is as follows:

Foundation excavation → graded crushed rock sub-base → C15 lean

concrete base course → rebar assembling → side formwork installing →

concreting → curing → cover slab installing

Steel side formwork will be used for service trench, which will be installed and

removed with the help of the crawler crane.

Concrete placing shall be divided into three times. Firstly, concrete of bottom

slab and side walls is to be cast; secondly, the pedestal for cover slabs is to be

cast to ensure its straightness; the central partition (only transverse trench) is to

be cast finally. The casting sequence is shown as below:

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Method Statement

Sketch of Sequence of Trench Concreting

After side formwork removal, concrete shall be cured timely in accordance with

relevant requirements, and it shall be kept damp not less than 7 days.

Qualified Cover slab will be installed by 65t auto crane after the pavement is

finished.

3.9.3 Sub-base

200mm thick graded crushed rock which lies on backfilled sand sub-grade after

compaction will serve as unbound sub-base for pavement; and 3084m3 graded

crushed rock will be involved in sub-base.

Construction for sub-base will be executed form west to east in section and in

one layer. And the procedure is as follows:

Prepare → graded crushed rock spreading → compacting

When the compactness of sub-grade has been accepted, setting out for graded

crushed rock sub-base can be executed, whilst graded crushed rock can be

stored and tested in accordance with design requirement or relevant codes.

Type SD23 bulldozer will be used for spreading for crushed rock; and partial

trimming and leveling shall be executed by manpower to ensure thickness and

level of the sub-base.

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Method Statement

Compaction should be carried out as soon as possible after crushed rock has

been spread according to the requirements and relevant codes.

Type LSS218B vibratory roller with static linear load 415N/cm will be used for

compaction. Basing on the design thickness of the sub-base is 200mm, 7 passes

will be executed for compaction in accordance with requirement.

Special care should be taken to obtain full compaction in the vicinity of both

longitudinal and transverse joints.

A minimum width of 2m of properly compacted sub-base beyond the edge of the

lean concrete should be prepared before actually placing the lean concrete.

3.9.4 Base Course

250mm thick lean concrete C15 which lies on the sub-base will serve as base

course for pavement; and the quantity of lean concrete is about 3855m3.

The construction sequence for lean concrete is stated as below:

Site prepare → formwork installation → concreting → curing

Setting out for lean concrete base can be executed after sub-base has been

accepted. Lean concrete will be constructed longitudinally in about 5m strips.

The staggered distance between longitudinal joints of lean concrete base and

upper layer pavement slab shall be more than 300mm; whilst the staggered

distance between transverse joints of lean concrete base and upper layer

pavement slab shall be more than 1m.

Concrete for base will be produced by our batching plant. And the slump

constant of lean concrete shall be met with the design requirement. Lean

concrete will be transported by mixer truck. It shall be constructed in one layer

and in strip along longitudinal direction of quay wall. Hand guided method shall

be adopted for concreting in a continuous process. Internal vibrator will be used

for compaction.

The side formwork shall be removed by labors. Curing liquid or fresh water shall

be involved in curing. Lean concrete shall be cured in accordance with relevant

requirements.

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Method Statement

3.9.5 Surface Course

430mm thick reinforced concrete C40 which lies on the base course will serve as

surface course for pavement, with the quantity of about 6631m3.

Construction for reinforced concrete will be executed transversely segment by

segment; and every segment of the reinforced concrete slab, which is in accord

with the design plan, will be cast in one layer. Its procedure is as follows:

Prepare → rebar prepare and erection → formwork installation →

concreting→ curing

When the lean concrete base has been accepted, setting out for reinforced

concrete slab can be executed, whilst reinforcement cages can be prepared.

Steel side formwork with reserved holes for dowel bars will be used for

reinforced slab. Formwork will be installed when reinforcement cages for

pavement slab have been finished. Dowel bars shall be installed after formwork

has been installed.

The concrete shall be produced by the batching plant in precast yard; it will be

transported to the quay site by mixer truck and will be cast by concrete pump.

Internal vibrator will be used for compacting concrete. Vibration quality shall be

ensured during casting, defects as honeycomb and big air voids should be

avoided. Finishing shall be performed when top elevation reaches, and concrete

finishing machine will be involved in leveling concrete surface. Screed by

manpower shall be used for leveling before initial setting of concrete.

Curing liquid will be sprayed when the concrete sets finally, and geotextile will be

covered subsequently. The damp curing will be applied at least 7 days. The side

formwork will be removed by labors when concrete compressive strength

reaches 10N/mm2. Then the contraction joint will be cut immediately after the

removal of side formwork.

3.10 Installation of Auxiliary Facilities

Auxiliary facilities, including bollard, fender, ladder, etc. will be installed after the

completion of capping beam and apron.

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Method Statement

Fender and Bollard Installation

3.11 Placement of Anti-scour Protection

Reno mattress, L*W*H=3000*2000*500mm, is designed for anti-scour protection

in front of quay wall. The construction sequence is as follows:

Site preparation → Mattress assembling → Foundation preparation →

Mattress installation.

A. Site Preparation

Mattresses, stone for mattresses and lifting frame should be prepared before

construction. The size of lifting frame is 6.0m in length and 2.0m in width， the

sketch is shown as follows:

The sketch of Lifting Frame

B. Assembly and Filling

The folded units shall be taken out from the bundle and placed on a flat ground.

Mattresses should be opened, unfolded and pressed out to their original shape.

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Method Statement

Front, back and end panels shall be lifted to a vertical position to form an open

box shape. End flaps shall be folded and overlapped, as appropriate. All edges

of the diaphragms and panels shall be tied or fastened to front and back of the

mattress. The mattresses should be assembled individually, by erecting the

sides, ends and diaphragms, ensuring that all creases are in the correct position

and the tops of all sides are level. Then, the edges of the mattress will be

connected by using lacing wire. When using lacing wire, cut a sufficient length of

wire and first loop and twist the lacing wire to the wire mesh. Proceed with tying

alternate double and single loops through every mesh opening approximately

every 100 mm, and pull each loop tight and finally securing the end of the lacing

wire to the wire mesh by looping or twisting. The lacing wire should be supplied

with the mattresses.

After being assembled, the mattresses shall be filled with rocks. Rocks for

mattresses shall be hard, angular to round, durable and of such quality that they

shall not disintegrate on exposure to water or weathering during the life of the

structure. Care shall be taken when placing the stone to avoid damaging the wire

coating. After a layer of rock has been placed in the cell, sufficient hand

manipulation of the rock shall be performed to minimize voids and achieve a

maximum density of the rock in the units.

To allow for settlement, fill more and level it off above the tip of the mesh. Then

lay the lid down and pull the edges of the panels to be connected. The lids shall

be tightly laced along all edges, ends and diaphragms in the same manner as

described for assembling.

C. Foundation preparation

The foundation on which the mattresses are to be placed shall be level to the

elevations as shown on the project construction drawings and surface

irregularities, loose material and vegetation in accordance with the project

specifications.

D. Installation

Finally, the mattresses shall be placed in their proper location and securely

attached to the adjacent ones. In principle, the mattresses will be installed by the

autocrane on the quay, and probably a few by crane on the barge.

Control for installation: When installing the mattresses, direction of the installing

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Method Statement

mattress should be controlled by the following steps. First, before the mattress

lifting underwater by crane with lifting frame, the location should be adjusted by

pulling ropes and moving the crane hook above the water. Then, diver shall dive

under water to adjust the location of the mattress by directing the crane until the

location is right. Finally, take off the hooks and make a mark on the capping

beam to record the installation location.

Placement of Reno Mattress

3.12 Fender Replacement and Concrete Repairs

The scope of this contract includes the installation of a fendering solution for the

following quay walls:

New quay to be constructed;

Existing quay wall of caisson construction (90m) ;

Existing quay wall constructed by Murray and Roberts (401m);

Existing quay walls constructed by CHEC (782 + 305m)

Existing dock quay walls constructed by CHEC either side of the heavy lift

dock (42 + 42m)

No fender repairs are required to the existing GRN quay or in the heavy lift dock.

The old concrete will be demolished by hydraulic breaker and removed from site.

Concrete will then be placed during interval. All these works will be carried out in

accordance with the programme and in such a way as to minimize interference

with the normal business of the Port and the Luanda Oil Service Centre.

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Documents

Preliminary Method Statement