06 4 iok a1 DRAINAGE SYSTEM

3.2 Reinforcing Steel for Concrete All reinforcing steel used in the works shall conform to the requirementsspecified in Section, “Reinforcing Steel and steel works” 3.3 Bedding... 4 De

NGAI SECTION

CHAPTER III:

CONSTRUCTION METHOD FOR DRAINAGE SYSTEM

I CONSTRUCTION METHOD FOR PILE CULVERT, BOX CULVERT AND

UNDERPASS BOX CULVERT

1 Description

This section described construction method for constructing new reinforcedconcrete pipe culverts, reinforced concrete box culverts, underpass boxculverts and storm water drains This work shall include headwalls, inletand outlet structures and reinforced concrete pipe cradles, as well asassociated erosion and scour protection works The Contractor will build all

of works in accordance with the Drawings and Specification and at thelocations indicated by the Engineer

2 Reference Standards

22TCN159-86: Specifications for construction and acceptance of

precast reinforced concreteTCVN 9116:2012: Pre-cast RC box culvert Technical requirements

TCVN 9113:2012: Drainage reinforced concrete pipe

TCVN 4453 – 1995: Monolithic concrete structure – Norm of

construction and acceptance

The construction of reinforced concrete box culverts, head walls, inlets,outlets and other reinforced concrete drainage structures shall be inaccordance with the provisions of Section “Concrete and ConcreteStructures”

3 Material requirements

3.1 Concrete

Concrete used for all structural work described in this Specification sectionshall be of the classes indicated on the Drawings and shall conform to therequirements specified in Section “Concrete and Concrete Structures”.All finished surfaces of concrete, which are not permanently covered shall;have a smooth fair finish, be even and free from waves, be finished true toline/levels and contours, be free of blow holes, be free of honeycombingand air bubbles and the like Any holes left by bolts used to position theformwork shall be filled in with epoxy grout flush with the surroundingsurfaces

3.2 Reinforcing Steel for Concrete

All reinforcing steel used in the works shall conform to the requirementsspecified in Section, “Reinforcing Steel and steel works”

3.3 Bedding

NGAI SECTION

Granular material for bedding shall be in accordance with Paragraph 4.2,Table 4 of Vietnamese Standard TCVN 7570-2006 and subject to theapproval of the Engineer

Lean concrete for bedding shall be class CIO bedding or blinding concrete

in accordance with the requirements of Specification Section “Concreteand Concrete Structures”

3.4 Stone Masonry

Stone Masonry and mortar used in the works shall conform to therequirements specified in Section “Stone Masonry”

3.4 Porous Backfill or Filter Material

In case of requirement in drawings, Porous Backfill or Filter Material shall

be in accordance with the provisions of Section “Porous drainage andBackfill” or as directed by the Engineer

3.5 Backfill

Filling material used in the works shall conform to the requirementsspecified in section “Excavation and Backfill for structure”

4 Detail construction method for pipe culvert, box culvert and

underpass box culvert

4.1 Preparation for construction

The Contractor shall furnish shop drawings containing the constructionsdetails for culverts and concrete drains indicated on the Drawings and asdirected by the Engineer Shop drawings shall be submitted to theEngineer prior to the start of the construction of culverts and concretedrains Construction of culverts and concrete drains shall begin only afterthe Engineer gives approval of the shop drawings to the Contractor

Temporary drainage work shall be in place and operating before beginningembankment works, or as directed by the Engineer

No subgrade preparation or pavement overlay work (either in the road orthe shoulder areas) shall commence until the culverts, headwalls, andother minor structures below the subgrade level along that particularsection of the project are complete

4.2 Construct for Precast Concrete Elements

Reinforced Concrete Culverts shall be precast reinforced concrete and shallconform with Specification Section “Concrete and Concrete Structures”.Pipes shall be laid with male/female joints and reinforcement in all pipesshall consist of spiral steel cages with longitudinal bars all as indicated onthe Drawings unless otherwise approved by the Engineer

Bearings to support the pipes shall be of the numbers and types indicated

on the Drawings and subject to the approval of the Engineer They shall be

to Site.

The Engineer shall periodically inspect the precast concrete manufacturingplants to ensure compliance with the approved method statements formanufacturing The Contractor will supply material samples for laboratorytesting to ensure quality compliance and will make the necessaryarrangements to facilitate the inspections by the Engineer

Such inspections shall include the inspection of reinforced precast concreteitems All precast items shall be marked with a unique reference and noitem shall be delivered to the construction Site without approval from theEngineer

In order to maintain the quality of the precast concrete items theContractor shall cast these in a factory off the Site

Execution of concrete, reiforced steel, formwork comply with therequirements specified in section “Concrete and Concrete Structures” Execution order is described as followings:

a) Preparation of casting area:

Units are casted in flat area, enough large to cast concrete and placingmaterial

The casting area is leveled and compacted to not be subside duringcasting and placing material as well as moving eqiupment and crane forinstallation units

The casting area is reinforced with concrete, thickness of concrete layer10-15cm

b) Preparation for material

All material for executing units, design for component of concrete mixturemust be approved by Project Manager prior to put in to use and complywith the requirements

c) Reinforced steel works

Reinforced steel is processed as Design Document which has beenapproved by Project Manager

NGAI SECTION

Steel is worked in to set for each culvert units Quantity of set for pouringconcrete daily must be accepted by Project Manager prior to the start ofthe execute of concrete

Reinforced steel works conform to the requirements specified in sectionTCVN 5709:2009 (Hot-rolled cacbor steel uses on construction) conform tothe requirements as indicated section, “Reinforcing Steel and steel works”.Installation of reinforced steel in to casting mould must ensure therequirement for thickness of protective concrete layer as specified inDesign Document Use the trestle to control the thickness of protectiveconcrete layer (if necessary) The trestle is made of material which assuresthe intensity and is similar colour to concrete and approved by ProjectManager

Installed-formworks ensure be firm and stable during placing concrete Theslab of formwork must be sealed to ensure not to loss the cement waterduring placing and compacting concrete

The forwork is removed as having result of testing sample for concreteintensity.The minimized intensity of concrete for removal formwork isapproved by Project Manager in the first test

e) Place and compaction of concrete:

Concrete is mixed by mixer according to mix design approved by ProjectManager

Concrete need to tested the slump before placing, sampling underwitnessed by Project Manager or authorized person

After pouring concrete on formwork, will be compacted with specializedequipment These equipments operate inside the narrow formworks,ensuring not to displace the steel bars or trestle The vibrator equipmentsattach outer surface of formwork are encouraged to use

Process of pouring and compacting concrete conform to the requirementsspecified in section “Concrete and Concrete Structures”

f) Concrete curing

Methods ang processes of concrete curing conform to the requirementsspecified in section “Concrete and Concrete Structures”

NGAI SECTION

g) Loading, transporting of concrete unit

Concrete units are only allowed to move out of casting area in case ofconcrete compressive strength for each sample in lift of concrete meets80% minimum compare with the requirement concrete strength for oneunit

Concrete units are put up and down carefully They will be transportedvertically to avoid impacting, bearing points and direction of reaction whentransporting and storing are as same as the last installation stage

All concrete units will be marked separate and permanent to write clearlytype of concrete unit and date of concrete

4.3 Construction of pipe culvert, box culvert and underpass box culvert at the site

a) Construction plan and organization

The positions of box culverts are for construction of service road; theservice road contractor shall carry out construction of entire culvert length

At the culvert positions that the service road or pipe culvert can not beconstructed, the contractor shall ensure transport by construction of 1/2the lower culvert first After that, the remained 1/2 culvert in the lowersection shall be constructed; these culvert shall be strengthened andopened to its edges by disposed stone or gravel aggregate foundation Theservice road shall be large enough for 2 directionally safe trafficmovement The service road shall be arranged with sufficient signal posts,signal plate, lighting (at night) with traffic control staffs at 2 endscontinually during construction period Horizontal drainage culvert shall bearranged temporarily for not affecting the culvert construction activities aswell as the existing discharge flow of the road, residential area andirrigational activities

b) Excavation of culvert trench

Excavation of culvert trenches will execute conform to the requirementsspecified in section “Excavation and backfill for structure”

Construction method and construction order as follows:

- Located the centre of culver, scope of trenches as Design Drawings;

- Removal of old structures (if any);

- Excavation of trenches by excavator, and using man-power forcompleting trenches Transporting waste material to regulated area

- Excavation of trenches with enough large (500 mm minimum from roadmargin which around the culvert) in order to execute body culvert andembank both sides of culvert Slope of trenches will be executedcomply with stability of trenches’s geology

- Constructing culvert at the location where water flows frequently will beuse cofferdam in method of constructing trenches It will be needed to

- If the soil in the trenches is mixed with quarry stone then the overelevated excavated area shall be backfilled by materials of littledeformation under pressure as sand, gravel sand or concrete with thesame mark with the trenches and shall be in compact with thefoundation The material type and compact requirements shall be inaccordance with regulated design documents or with the instructionsfrom the Engineer.

- Structures of blinding stone and concrete of culvert foundation will beonly allowed install when trenches be executed as Design Drawings, beaccepted by Project Manager

c) Instalation of precast units

The Contractor shall lay reinforced concrete cradles and pipes carefully.The hubs or grooved ends shall be up grade The spigots or tongued endsshall be fully entered into the adjacent hub or groove and be true to therequired lines and grades

Before laying succeeding sections of reinforced concrete pipe which do notrequire cambering, the Contractor shall plaster the lower half of the hub ofthe preceding sections on the inside with Portland cement mortar Themortar shall be sufficiently thick to bring the inner surface of the abuttingpipes flush and even The Contractor shall plaster the upper half of thespigot of the succeeding pipe with mortar at the same time

All Pipe or Box Culverts shall be laid and fitted together such that the jointsealant forms a full and effective seal around the full circumference of thePipe or the Box Culverts Joint sealants shall be placed such that any joints

or overlaps in the sealant are at the top of the Pipe or the Box Culverts.After laying the reinforced concrete pipe, the Contractor shall fill theremainder of the joint with sufficient mortar to form a bead around thejoint The Contractor shall wipe the inside of the joint and finish it to asmooth and even surface The mortar on the outside shall be cured andremain damp for two days or until the Engineer allows backfilling toproceed

d) Culvert Headwalls, Inlets, and Outlets

Unless otherwise shown on the Drawings, the Contractor shall construct allculvert aprons, wing-walls, and headwalls using reinforced concrete of theclass indicated on the Drawings and in accordance with requirements and

- Spreading blinding stone for culvert foundation;

- Construction of bedding stone and foundation lean concrete;

- Installation of reinforced steel, pouring concrete for bottom slab of bodybox culvert;

- Installation of reinforced steel, pouring concrete for bodywall and face slab

of culvert;

- Execution of headwalls, wingwalls, structure of inlets, outlets

- Execution of mortar stone structure, reinforcing slope of headculvert,reinforcing to unti – erosion of culvert downstream

- Installation of over slab when filling soil to design elevation

All works for executiong concrete, reinforced steel, formwork conform tothe requirements specified in section “Concrete and Concrete Structures”.Furthermore, these works need to comply with specific requirement asfollows:

Reinforcement erection in accordance with the design drawings The

steel bars are discalced and cleaned Reinforcement connection methods aswelding or binding shall be carried out right in accordance with regulations.Reinforcement frames, fenders or rebars shall be laid on the skids; thecement skids have the similar thickness to the protection concretethickness; the steel cable shall be lined in the skids to bind them on thereinforcement The skids laid on the suitable positions basing on thereinforcement density but not over 1m from a skidding place The salvageshall not be used to skid the outer surfaces of the structures Frame andfender of the reinforcement shall be binded tightly and not deflecting wheninstalled in the platform and during concrete casting The pre-erected parts

do not affect to the parts erected afterwards The reinforcementinstallation shall be accepted by the SC before concrete casting

Erection of the reinforcement platform: Before erection, the platform

shall be cleaned and an anti-adhesive oil layer shall be applied The platformshall be erected by crane in cooperation with manpower and closelyconnected by bolts It shall be noted to erect the scaffolding and bearingbraces to ensure the stability of the platform during concrete casting Thecleats shall be arranged for easy disassembling of the scaffolding andplatform when the concrete reaches the allowed strength

NGAI SECTION

Concrete casting and vibration: Equipments and materials as well as

manpower shall be checked before concrete casting The materials shall besufficient for continuous concrete casting and the concrete batchingmachine shall operate well

- Concrete casting-in-situ shall be done by batching machine and crane.Concrete shall be casted in the silo right after poured out from thebatching machine Crane shall be used to take to concrete to right place

- During casting, sample shall be taken to test the slump of the concretefor adjustment as in the design Sample shall be casted for later test.The aggregate measurement system shall also be checked to ensure thedesign batching ratio for concrete

- Concrete transference chute shall not be over dip, the free falling height ofthe concrete shall not be overt 1m because of making concretestratification

- The upper concrete layer shall be casted and vibrated before theconcrete layer below starts to freeze

- Concrete shall be well vibrated right after casted

- If the needle vibrator and plate vibrator are used, then the maximumthickness of the concrete layer shall be as follows:

+ If the needle vibrator is used, the concrete layer thickness shall be by1.25 of the effective length of the needle arm

+ If the plate vibrator is used, the concrete layer thickness shall be12cm for the structure with much reinforcement, or shall be 25cm forthe non-reinforcement structure

+ The distance for needling the vibrator shall not exceed 1.5 time of theeffective radius of the vibrator The vibrator shall not penetrate to thelower concrete layer casted before, if this layer is freezing

- If the plate vibrator is used, then the vibrating marks shall overlapped by

4 - 5cm Vibrating through the reinforcement shall not be done

- Concrete casting shall be done continuously until part by part of theconstruction works is completed

Concrete maintenance: After concrete casting no later than 10 -12 hours

in winter or 4 - 5 hours in summer, watering shall be done and theconcrete surface shall be covered in 7 days and 7 nights; if thetemperature exceeds 150C, then watering shall be done in the first 3 daysand 3 nights: in daytime, watering shall be done after every 3 hours and in

NGAI SECTION

night time, watering shall be done for 1 – 2 times, then at least 3 times ofwatering in a night is required

Platform disassembling: Culvert wall platform (the non-load-resistant,

non-strength-resistant structure) shall be disassembled when the concretereaches the strength of minimum 25kg/cm2 For the strength-resistantscaffolding and platform, concrete shall reach 70% of the designedstrength then the platform can be disassembled The platform disassembleshall be done carefully for not creating the thrust to the concrete structure.Before and after strength-resistant platform disassemble, the slump of thedeformation area and structure shall be measured

4.5 Backfill

Backfill of foundation pit and fill material both side of culvert comply withthe requirements specified in Section “Excavation and backfill forstructure”

The Contractor shall not backfill any pipe until the Engineer inspects andapproves the site conditions The Contractor shall backfill and compact thesoil around and over the reinforced concrete culvert pipes in accordancewith the requirements specified in Section “Embankment Construction”and “Excavation and backfill for structures”

The Contractor shall take the fill to a minimum height of 500 mm abovethe top of the pipe Unless in a trench, the fill shall extend for a minimumdistance of one and a half diameters from the centerline of the pipe oneach side of the pipe The Contractor shall take special care to compactthe backfill under the haunches of the pipe properly The backfill shall bebrought up evenly on both sides of the haunches for the entire pipe length.Heavy earth moving and compacting equipment shall not operate closerthan 1.5 meters from the culvert until the cover above the pipe is at least

500 mm Light weight equipment may operate within the limitationmentioned above provided the backfill is placed and compacted at least

300 mm above the top of the pipe Notwithstanding these conditions, theContractor shall be responsible for and shall rectify any damage resultingfrom such operations

4.6 Cleaning Culverts

The Contractor shall clean all culverts until they are free of loose debris,soil, and all foreign material The Contractor shall keep the culverts cleanand maintain them in an operating condition throughout the ContractPeriod The Contractor shall only permit water to flow through the cleanedculvert after the Engineer inspects and approves the culvert

4.7 Quality assurance method

a) Pipe culvert quality assurance method.

Pipe culvert shall be laid at right positions, straight to the longitudinalsection of the pipe culvert and suitable to the natural flow

The inner and outer surfaces of the pipe culvert shall be flat and smoothwith no crack, porosity or roughness

-Pipe culvert body -10; +5 ± 10 - ± 5

The following parameters are noted in detail on each component of the casted concrete pipe culvert body:

pre Type of pipe culvert and inner diameter;

- Date of casting;

- Lot number of products;

- Product testing results;

- Name and code of typical drawings of applied pipe culvert components

- Pipe culvert with one of the following features shall be discarded:

+ Serious cracks or crazes;

+ Defects due to unsuitable mixture ratio and under-required batchingand vibration;

+ Porosity or breaking; reinforcement sticks out;

+ Reinforcement sticks out or serious displacement of reinforcement(checking is carried out by ruler to measure the concrete layer);

+ Pipe culvert opening is damaged or cracked, broken (these damagesinconvenience the connection joint construction)

Checking the elevation, dimension and geological conditions of foundationbedding: Before culvert foundation construction, the foundation pit ischecked with elevation, dimension and geological conditions of foundationbedding by the SC The construction of the next parts of the box culvertshall only be carried out with the approval in writing of the SupervisionConsultant

Culvert shall be laid at the easy water discharge position; after laid, culvertshall be straight, at right elevation and gradient as designed Error ofculvert bedding elevation is ±10mm, assuring the uniformity of the outletand inlet of the culvert

The outlet and inlet of the culvert shall be strengthened; the absorptionbasin shall be at designed dimension

The tightness of embanked soil layer in the foundation pit, culvert openingand culvert top shall be checked regularly before carrying out the nextlayers