Method of structure excavation a1 ENG s1

This work defines and describes the cutting and excavation of the original ground atlocations where pile cap or footings, box culvert and other structures are to be in placed inaccordanc

Trang 1

1 General 3

2 General Locations 3

3 Construction Schedule 9

4 Site Organization Chart 9

5 Materials 10

6 Equipment and Tools 11

7 Major Types of Structure Excavation 11

a 7.1 Structure Excavation without Temporary Cofferdam 12

b 7.2 Structure Excavation with Temporary Cofferdam 17

8 Quality Control 23

9 Safety Control 23

10 Environmental Control 24

Appendixes

(Structure Excavation without Temporary Cofferdam) 4 Pages Attached

Appendix II - Typical Construction Sequence

(Structure Excavation with Temporary Cofferdam) 5 Pages Attached

Total 36 pages

1 General

Trang 2

Structure Excavation shall be undertaken in accordance with Section 03200 of the GeneralSpecifications This method generally applied to the Structure Excavation for Foundation ofBridge, Culvert, Sub-drain, Box Culvert, and other structures as directed by the Engineer This work defines and describes the cutting and excavation of the original ground atlocations where pile cap or footings, box culvert and other structures are to be in placed inaccordance with the designed bottom elevation.

Excavation for Structures such as Box Culvert and Abutment located at Embankment areasand on Soft Ground conditions shall be in accordance with the Engineer’s instruction forresidual settlement due to consolidation

Where the Engineer orders the excavation after embankment has been placed, this extraexcavation in the embankment will be measured for payment as Structure Excavation

Backfilling and restoration works of adjacent area on completed structures, disposal ofunsuitable excavated material, dewatering works and related works to free the accumulation

of ground water and artificial run off water inside excavated area shall be part of StructureExcavation except the removal or diversion of existing water flows Excavation shall bedone in accordance with the lines and grades as indicated on the approved workingdrawing Accurate quantity will be calculated based on approved working drawing

2 General Locations

Location and intended type of excavation is shown as below table Detail shall be indicated

on the working drawing

without cofferdam

Excavatio

n with a part of cofferda m

Excavati

on with cofferda m

A7/01 Chau Que

Thuong bridge Km190+487.35 A1,A2 P1,P2

A7/02 Khe Sang

Bridge Km191+353.15 A1,P1,P4,P5,P6,P7,P8 P2,P3

A7/03 Khe Hong

Bridge Km193+379.65 A1,P3,,P4,A2 P1,P2

A7/04 Tan An Bridge Km194+765 A1,P2,P3,P4,P5,A2 P1

A7/05 Khe Can

A7/07 Thin Thung I

Bridge Km199+050.50 A1, P1,A2

A7/08 Thin Thung II

Bridge Km199+131.40 A1, P1,A2

A7/09 Tan Thuong Km199+860 A1,P1,P3,A2 P2

Trang 3

Tan Tien Bridge 209+329.70Km P2,P3,P4.P5 　 A1,A2,P1

A7/14 Cam Con

culvert Km191+960.00 Without cofferdam

A7/03C Pipe culvert Km191+980.00 Without cofferdam

A7/17C

Underpass Box

A7/19C Pipe culvert Km195+137 Without cofferdam

Trang 4

A7/20C

Drainage Box culvert Km195+674.00 Without cofferdam

A7/25C

Underpass Box

Km197+032.

00

Without cofferdam

A7/40C

Underpass Box culvert Km203+420 Without cofferdam

A7/41C

A7/42C

A7/43C

A7/44C Underpass Box Km206+239 Without cofferdam

Trang 5

A7/45C

A7/46C

Drainage Box culvert Km202+380 Without cofferdam

A7/47C

A7/48C

A7/49C

A7/69C

Underpass Box culvert 2.70x4.00 Km207+452 Without cofferdam

A7/70C

A7/71C

A7/72C

A7/73C

A7/74C

A7/75C

A7/76C Underpass Box Km211+035 Without cofferdam

Trang 6

culvert 2.70x4.00

A7/77C

A7/78C

A7/79C

A7/80C

A7/81C

A7/82C

A7/83C

A7/84C

A7/85C

A7/86C

A7/87C

A7/88C

A7/89C

Drainage Box culvert (3.0x3.0) Km210+120 Without cofferdam

A7/90C

Drainage Box culvert 2(3.0x3.0) Km211+051

Without cofferdam

A7/91C

Without cofferdam

A7/92C

Trang 8

km210+024-Without cofferdam

3 Construction Schedule

Construction Schedule shall be referred to latest approved Overall Schedule and to beupdated monthly and weekly For each location, schedule for structure excavation shall besubmitted together with working drawing

4 Site Organization Chart

Trang 9

Organization chart for management and construction of structure excavation work is asfollows:

5 Materials

The proposal of materials will be submitted to the Engineer for approval and material tests

in laboratory shall be carried out prior to commencement of work under the Inspection bythe Engineer

The general description and list of materials is as follows The detailed information formaterial shall be submitted separately as proposal for materials

Trang 10

5-1 Material List

List of required material is shown below

6 Equipment and Tools

Table1 - List of Minimum Equipment and Tools

Note:

Above stated schedule of equipment shall be increased in quantity if required andnecessary

7 Major Types of Structure Excavation

Generally, Structure Excavation without Temporary Cofferdam will be applied However,Structure Excavation with Temporary Cofferdam shall be applied depending on thefollowing cases:

1 Structure is located on or adjacent to existing pond, canal and channels

2 Structure is located on or adjacent to existing roads or highways and importantfacilities

3 Actual conditions after verify and ascertain the reasons and factors for application ofTemporary Cofferdam and after approval by the Engineer

Trang 11

4 Design and proposal for application of cofferdam has been approved by theEngineer at locations where structure excavation without cofferdam is not feasible

In addition, in case of structures are located adjacent to existing road and excavation depth

is not so deep (≤ 3m) then excavation may be carried-out with a part of steel sheet pilecofferdam It means only temporary steel sheet pile wall at existing road side shall beapplied This structure excavation shall be applied for abutment or pier adjacent to existingroad of all flyover bridges

a 7.1 Structure Excavation without Temporary Cofferdam

This describes the direct excavation of existing ground and hauling out of excavatedmaterials inside the area of excavation for the construction of structure Excavation workshall be checked and shall be done carefully to prevent and avoid damage or disturb thesubsoil

In case the foundation material is found unsuitable material, removal and replacement shall

be confirmed by the Engineer

Open cut trenches and foundation pits shall have enough clearance for working area forconstruction of foundations and base of structure

Typical Construction Sequence for Structure Excavation without Temporary Cofferdam isattached on Appendix I

7.1.1 Typical Construction Flow

Trang 12

Confirmation of Approved Material

Acceptance Commitee for Cast-In-Place

Granular Backfill

Check Ground Condition Working area preparation.

Confirmation of Working Drawing for Cofferdam Site Clearance and Demolition

Confirmation of Subsoil Foundation by the Engineer Inspection of limit and Elev Bott of Blinding Stone Confirmation of Approved Material

Pile Head condition Check Elevation of Cut-Off level and

Confirmation of As Built for Cast-In-Place

Method Statement shall be submitted separately

Confirmation of Compaction by the Engineer

Set survey marking points

Trimming/Leveling Works

Placing of Blinding StoneFormworks setting/

Backfilling /Restoration Works Pile Cap Construction Casting of Lean Concrete

Pier Construction Pile head Treatment

Cutting and Excavation Works/

Check the location of pump pit and temp drain.

Inspection of limit and Elev Bott of Lean Concrete

Structure Excavation without Cofferdam

Hauling out of Excavated Material Temporary Drainage

"Procedure of construction" "Action to be taken"

Preparation Work

Establish Limit of Work Confirmation of Topographic Survey of Orig ground

Check slope of excavation Construction

by the Engineer

Check existing soil formation (unsuitable material)

Inspection and Approval of Bottom Elev of Excav.

Confirmation of Approved Material

Confirmation of As built for Structure Method Statement shall be submitted separately

7.1.2 Construction Method

7.1.2.1 Preparation Work

Trang 13

Confirmation of Working Drawing including Site Layout plan The type ofStructure Excavation shall be shown on Working Drawing

Prior to starting excavation operations in any area the Contractor shall:

 Take steps on his own initiative to regulate the natural drainage of the waterflows on the surface of the ground to prevent flooding of excavation

 Ensure that all necessary site clearance and demolition in that area has beenperformed in accordance with these Specifications

 Notify the Engineer sufficiently in advance of the beginning of anyexcavation so that cross sectional elevations and measurements can be taken

of the undisturbed ground The existing ground adjacent to the structure shallnot be disturbed without the permission of the Engineer

7.1.2.2 Establish Limit of Work

Establish excavation limit including the working area inside excavation andshall be in accordance with the approved working drawing Topographic survey

of original ground which had been approved shall be applied to calculate thequantity for structure excavation Average elevation of original ground shall becalculated based on topographic survey The elevation of the bottom of siteclearing shall be 20cm below the average elevation of the original ground Depth

of 20cm below the average elevation of original ground shall be under SiteClearing works Excavation below bottom of site clearing shall be applied tostructure excavation Such elevation shall be shown on working drawing.Marking elevation shall be provided prior to excavation at site

7.1.2.3 Cutting, Excavation and Trimming Works

7.1.2.3.1 First step of excavation shall be undertaken using excavating

equipment Bottom of excavation shall be up to 20cm average abovethe designed bottom of structure excavation Depths shall be checkedand monitored carefully to prevent damage and disturb the subsoil offoundation

7.1.2.3.2 Pumping pit may be provided located at one or two corners inside the

excavation area Temporary drain canal sloping towards the pumpingpit may be provided around the perimeter of the excavation pit andmay be constructed outside the perimeter of the lean concrete.Location of pumping pit may be shown on submitted workingdrawing

7.1.2.3.3 Excavated materials found to be suitable for backfill and embankment

shall be hauled to a designated area and shall be protected to keep dry.Unsuitable materials upon approval by the Engineer shall be disposedseparately The vertical sides of the excavation shall be slopedapproximately to a minimum of 1:0.5 for good stability The slopemay be properly covered with plastic sheet against soil collapse anderosion during rainfall During excavation, care shall be taken in

Trang 14

consideration not to damage the Cast-in-Place piles at locations wherepile cap or footing are to be in-placed.

be done on the remaining 20cm average from the first step ofexcavation up to the designed bottom elevation of structure excavation.The base shall be compacted using a portable compacting machine orequivalent In cases that unsuitable or soft material still exists at thedesigned bottom elevation of excavation, removal and replacement ofsuch will be checked and confirmed by the Engineer If found to beunsuitable material it shall be removed and replaced

7.1.2.3.5 After completion of excavation, all loose and displaced material shall

be removed, leaving a neatly and solid finished bed for construction offooting or pile cap or base of box culvert and other structures

7.1.2.3.6 Substructure and Base foundation limit shall be marked with survey

stakes for setting up boundaries of the blinding stone, lean concreteand pile cap

7.1.2.3.7 Completed Excavation shall be Inspected and Approved by the

Engineer prior to construction of any permanent bedding or structure.Same procedure shall be done for base of box culvert and otherstructures

7.1.3 Blinding Stone

7.1.3.1 Establish limit of boundaries of blinding stone for setting side forms

7.1.3.2 Approved material for Blinding Stone shall be placed following the

submitted working drawing The in-placed blinding stone shall becompacted thoroughly to the satisfaction of the Engineer usingportable compacting equipment or equivalent At the area around thecast-in-place pile, a mechanical rammer or equivalent equipment shall

be used in the compaction taking care not to damage concrete piles.Tolerance on thickness and elevation shall be ±20mm

7.1.3.3 Completed blinding stone shall be inspected and approved by the

Engineer prior to construction of lean concrete layer

7.1.4 Lean Concrete

7.1.4.1 Lean concrete shall be placed to the elevation and thickness as

indicated on working drawing and shall be cast within the definedboundaries by setting side forms Placing shall be carried out either bydirect pouring, excavator or by crane and concrete bucket

Định dạng
Số trang	26
Dung lượng	745,5 KB