Method Statement for BaseSlab Concreting:
METHOD STATEMENT
FOR
Base Slab Concreting
Table of Contents
1. PURPOSE -------------------------------------------------------------------------------------------- 2
2. SCOPE ------------------------------------------------------------------------------------------------ 2
3. RESPONSIBILITIES ------------------------------------------------------------------------------- 2
3.1 Project Manager ----------------------------------------------------------------------------------------------------------------------- 3
3.2 Station Manager ----------------------------------------------------------------------------------------------------------------------- 3
3.3 Site Engineer ---------------------------------------------------------------------------------------------------------------------------- 3
4. DEFINITIONS ---------------------------------------------------------------------------------------- 3
5. REFERENCES -------------------------------------------------------------------------------------- 4
6. METHODOLOGY: ---------------------------------------------------------------------------------- 4
6.1. Instrumentation and monitoring ------------------------------------------------------------------------------------------------- 4
6.2. Excavation works: --------------------------------------------------------------------------------------------------------------------- 4
6.3. Preparation of diaphragm wall surface and exposure of couplers: ---------------------------------------------------- 5
6.4. Preparation of Formation ----------------------------------------------------------------------------------------------------------- 5
6.5. Placing of PCC/Blinding concrete ------------------------------------------------------------------------------------------------- 6
6.6. Application of waterproofing ------------------------------------------------------------------------------------------------------ 6
6.7. Installation of Rebar ------------------------------------------------------------------------------------------------------------------ 6
6.8. Formwork -------------------------------------------------------------------------------------------------------------------------------- 6
6.9. Concrete production and transportation --------------------------------------------------------------------------------------- 6
6.10. Compaction of concrete ------------------------------------------------------------------------------------------------------------- 7
6.11. Surface Finishing ----------------------------------------------------------------------------------------------------------------------- 7
6.12. Curing of concrete --------------------------------------------------------------------------------------------------------------------- 7
6.13. Removal of Formwork:--------------------------------------------------------------------------------------------------------------- 8
7. SAFETY ----------------------------------------------------------------------------------------------- 8
8. QUALITY --------------------------------------------------------------------------------------------- 8
9. EQUIPMENTS --------------------------------------------------------------------------------------- 8
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Method Statement for BaseSlab Concreting:
1. PURPOSE
This document sets out the Work Method Statement for Base Slab concreting, in order to carry
out the works in planned and systematic manner .
2. SCOPE
To set out the requirements for Base slab concreting for MMRDA/9/MMRP/CA48 Project to
meet all the contract requirements and JKIL standards for work operation, safety, quality and
environmental compliance. This Method Statement applies to station/Shaft works having top
down methodology construction.
This includes the following.
Excavation upto formation level of Base slab
Preparation of D’wall and exposure of coupler
Placing of PCC
Waterproofing works
Concreting
Curing
3. RESPONSIBILITIES
The MS shall be followed by all personnel involved in construction activity.
This MS may be adjusted to suit adverse site conditions subject to approval of
Station Manager.
Action may be delegated, but responsibilities shall not be delegated.
Use of word ‘shall’ with in this document indicates a mandatory requirement.
Use of word ‘should’ within this document indicates a preferred requirement.
Detailed responsibilities are set out in:
o Project Quality Management Plan
o ITPs
o Risk Assessment
o SHEVCs
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Method Statement for BaseSlab Concreting:
3.1 Project Manager
The approval of this MS
Overall scope of work.
Coordination of personnel and equipment to ensure continuous program of works
during execution.
Receiving daily progress reports and distributing to Client’s approved representative
and Contractor’s Management, and ensuring prompt action to any matter highlighted
in the same.
3.2 Station Manager
Implementation of this MS.
Safety to personnel, incident reporting and implementation of the Safety
Management Plan and Safety Management System.
Ensuring that the works are carried out in accordance with approved permits and
MS.
Ensuring that all personnel are fully aware of their duties and responsibilities.
Liaising with Client’s approved representative during the operations and during MS
change, contingency operations or mitigation works.
3.3 Site Engineer
Ensuring construction is in accordance with approved MS and specifications.
Ensuring that all data is recorded in accordance with this document.
Ensuring all required as built data are recorded.
Providing any information and field calculations that may be required during the
work.
4. DEFINITIONS
For the purpose of this document the term:
JKIL : Contractor
QA : Quality Assurance (applies essentially to process)
QC : Quality Control (applies essentially to works and
Page 3 of 8
Method Statement for BaseSlab Concreting:
products)
ITP : Inspection& Test Plan-A document that sums up all the
information related to inspections, measurements and
tests to be carried out during execution of work in scope.
For the scope, the term ITP is used.
Shall : Mandatory Requirement
Should : Recommended Practice
SHEVC : SHE verification checklist
5. REFERENCES
Applicable Specifications - refer to Attachment 1
Applicable Project Procedures - refer to Attachment 1
Applicable Project MSs - refer to Attachment 1
Applicable Drawings & Sketches – refer to Attachment 2
6. METHODOLOGY:
Baseslab construction shall be performed according to the following Sequence:
6.1. Instrumentation and monitoring
Monitoring of ground settlement and water table measurement shall be carried out
throughout the construction works by continuing reading at the installed piezometers,
inclinometer and standpipes (If required).
6.2. Excavation works:
Permit to dig shall be obtained from the designer prior to carrying the excavation works.
Excavation of soil to formation level:
o Excavate the soil down to the formation level using mechanical excavator with a
long boom.
o Use dump trucks to haul the excavated material to the dumping ground.
o Progressively carry out spot level survey and conform the formation level.
o Excavate down further beside the diaphragm wall where and as shown on the
drawings.
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Method Statement for BaseSlab Concreting:
o Adjust the formation level (lower), where the lower couplers slightly out of
position (lower than the designed level) but within the allowable limits.
o Water table will always be maintained below final excavation level and drainage
layer (wherever applicable) shall be prepared as per approved MS.
6.3. Preparation of diaphragm wall surface and exposure of couplers:
Currently with the excavation for the base slab, the surface shall be prepared as
mentioned under:
Couplers shall be exposed by chipping off the concrete surface using electric
chipping machine.
Following points should be noted while doing this operation
o Care shall be taken to ensure that the rebars shall not be exposed unnecessarily.
o Chipping shall be limited to exposing the sound concrete surface only.
o Chipping should be carried out in a manner that cracks are not
formed/propagated.
All loose and unsuitable material/concrete shall be removed using water/air pressure
wash. The blackouts in the diaphragm wall for the base slab shall be removed and
the cast in couplers shall be located in the diaphragm wall. In the event of cement
grout found in the inner threads of couplers, it shall be cleaned by wire brushes and
compressed air. A threader may be used if required.
In case of missing couplers or couplers out of position beyond tolerance, the same
shall be treated as per guideline given by designer.
The surface of diaphragm wall shall be in contact with base slab shall then be
roughened to provide a good joint between the old and new concrete. Beside recess
shall be made in the D’wall along the coupler location.
6.4. Preparation of Formation
After completion of excavation to the formation level, relevant gridlines shall be set out
and the area for the PCC/blinding concrete shall be levelled and compacted. The area
shall be free from mud and after and trimmed clean. All soft or defective materials shall be
cut and replace with suitable materials. After levelling and compaction of the formation,
survey check shall be carried out to confirm the level of the prepared formation.
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Method Statement for BaseSlab Concreting:
6.5. Placing of PCC/Blinding concrete
PCC/ Blinding concrete of required thickness shall be placed manually or mechanically.
Concrete shall be levelled and finished to ensure uniformity.
6.6. Application of waterproofing
Method statement for application of waterproofing shall be followed.
6.7. Installation of Rebar
Fixing of steel reinforcement bars inclusive of bar chairs, couplers shall be carried out in
accordance with approved rebar drawings. Following fixing sequence shall be generally
being followed:
Marking out gridlines and construction joint on the D wall face.
Install first layer of bottom reinforcement on cover blocks with appropriate dia bars
and Install top reinforcement over the bar chairs.
Install level markers for the finishing level of the baseslab concrete. The surveyor
shall mark a level line on the diaphragm wall to show base slab surface.
The rebar shall be cut and bent as per approved construction drawings at the rebar
yard and shall be accurately placed, securely fixed using tying wire and adequately
maintained in position shown on the approved drawings.
Dowels shall be suitably left for the construction of UPE duct, service gallery
escalator pit, lift pits. Permanent column and STUB columns.
6.8. Formwork
Formwork shall be required for following:
Plug all through holes (opening around starter bars) in the formwork.
To form the sides of the slabs around the main access openings and other smaller
openings.
Formwork shall be externally supported by suitable bracing & will be strutted all
along the length of formwork.
6.9. Concrete production and transportation
Concrete (Grade: M40 mix with crystalline water proofing material) shall be
produced at JKIL. batching plant and transported by 7.0 m 3transit mixer to site.
Approved concrete mix shall be placed as per approved concrete pouring plan.
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Method Statement for BaseSlab Concreting:
Concrete pump with pipeline shall be used for pouring of concrete to pour area.
Pouring rate of concrete shall be minimum 40cum/hr unless it can be demonstrated
that pouring rate below this level shall not lead to cold joints. A flexible hose shall be
attached to the end of the concrete pipeline to deposit concrete as nearly as
practicable in its final position.
Prior to the commencement of pumping of concrete by concrete pump, 0.3-1.0m3 of
cement slurry shall be pumped for lubricating the pipelines. After this, concrete shall
be taken in pipe line. Slurry coming out of pipe shall be discarded and the concrete
shall be poured inside the formwork. Concrete for the base slab shall be placed in
layers. Each layer shall be compacted before the next layer is placed in layers.
Concrete shall be placed in final position and after that adequate vibration shall be
given for compaction.
Sufficient manpower shall be provided to ensure the surface does not get dried up
before finishing.
Operation shall be full systematically and competently supervised ensuring all
precautions for drying of concrete is provided. Back-up equipment shall be in place.
6.10. Compaction of concrete
Concrete shall be compacted during placing by immersion vibrators 60mm dia penetration
vibrators shall be used at grid of 300mm c/c. Immersion vibrators shall be operated in
near vertical position and shall penetrate the full depth of the layer of concrete placed and
just into the layer below. Vibration shall be applied continuously until the expulsion of air
has practically ceased. The vibrator shall be withdrawn slowly to avoid the formation of
voids. During the compaction, care shall be taken to avoid the displacement of
reinforcement, formwork, pre-fixed pipes, blockouts, thermocouples, etc.
6.11. Surface Finishing
Surface finish for the PCC concrete and base slab concrete shall be done at the required
level.
6.12. Curing of concrete
The following procedures shall be followed in curing the slab concrete:
Curing shall be done with water which is found suitable to be used as mixing water
for concrete (As per IS 456:2000).
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Method Statement for BaseSlab Concreting:
Wet hession cloth shall be spread over the concrete surface or curing shall be done
by ponding.
6.13. Removal of Formwork:
The side forms at construction joints shall be struck after 24hrs.
7. SAFETY
Risk Assessment report attached as attachment 3 shall be used.
Workers will wear helmets, Safety shoes/ Gum boots while working on site.
Watchman will be available at each work site both during working and
non-working hours.
All excess excavated material, concrete, etc. will be cleared regularly.
During excavation, watering platform around the panel shall be maintained clear
of slurry, concrete, water enchanted material etc. so that safe access is
available.
8. QUALITY
Inspection Test Plan attached as appendix 4 shall be used.
Concrete shall be placed in its final position within 2 hrs of the introduction of
cement to aggregates.
9. EQUIPMENTS
List of Equipment attached as appendix 6 shall be used.
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