Table of Contents

    Methodology for Bridge Pile Foundation

    1. Scope

    This method statement covers boring and construction of pile foundations for Minor Bridges and ROBs in accordance with approved drawings, IS:2911 (Part-1), and MoRTH Specifications.

    The work includes boring, reinforcement fixing, tremie concreting, and quality control of cast-in-situ bored piles.

    2. References

    • Contract Agreement
    • IRC: SP: 84-2014
    • MoRTH Specifications (5th Revision)
    • Relevant Approved Drawings
    • IS:2911 (Part-1)

    3. Setting Out

    1. The center line and benchmark of each bridge/structure shall be established with reference to project center line and approved by the AE.
    2. Reference points for X-X axis and Y-Y axis shall be fixed using Total Station.
    3. At least two permanent benchmark/reference points shall be established on either side of the bridge at safe locations away from construction activities.
    4. Center line and benchmark points shall be transferred to each pier and abutment location while maintaining safe offset distances.
    5. Pile layout shall be established using approved coordinates before commencement of boring operations.
    6. All working reference points shall be checked jointly with the AE and recorded in site records.

    4. Working Drawings

    Working drawings, structural drawings, and relevant details shall be submitted to the AE before commencement of work.

    After review and approval by the AE, setting out and construction activities shall be carried out.

    Test piles shall be executed as per reviewed drawings and Clause 1105 of MoRTH Specifications.

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    5. Materials

    All materials shall conform to Section 1000 of MoRTH Specifications.

    • Structural steel shall conform to Section 1600.
    • Concrete shall conform to Sections 1700, 1800, and 1900.
    • Reinforcement steel shall conform to approved drawings and relevant IS codes.

    6. Equipment & Machinery

    • Piling Rig / Percussion Machine
    • Lifting Crane
    • Dumpers
    • Batching & Mixing Plant
    • Transit Mixer
    • Concrete Pump
    • Concrete Vibrators
    • Vibrator Needles
    • Bar Bending Machine

    7. Personnel for Execution & Supervision

    Experienced and trained personnel shall be deployed for pile construction activities.

    Reinforcement cage inspections shall be carried out by the Sr. Structural Engineer / DPM to ensure compliance with approved drawings and specifications before lowering into boreholes.

    8. Construction Operations

    8.1 Boring Operations

    1. Cast-in-situ bored piles shall be constructed by boring into the ground and removing excavated material.
    2. Boring shall be carried out using rotary drilling equipment.
    3. Pile diameter shall not be less than specified in approved drawings.
    4. Continuous records shall be maintained regarding boring depth and volume of concrete placed.
    5. Bentonite slurry or approved drilling mud shall be maintained above groundwater level throughout boring operations to ensure bore stability.
    6. Borehole verticality and alignment shall be checked periodically during drilling.

    8.2 Reinforcement Cage Lowering

    1. Reinforcement cages shall be fabricated as per approved BBS and drawings.
    2. Cover blocks and spacers shall be fixed to maintain required cover.
    3. The reinforcement cage shall be lowered carefully without disturbing bore stability.
    4. Proper lifting arrangements shall be used during cage lowering operations.

    8.3 Concreting Operations

    1. Wherever practicable, concrete shall be placed in a clean and dry borehole.
    2. Before concreting, it shall be ensured that no loose material or debris remains at the bottom of the bore.
    3. Concrete shall be placed using tremie pipe continuously from pile toe to pile top.
    4. The bottom end of tremie pipe shall always remain embedded in freshly placed concrete.
    5. Concrete placement shall be continuous without interruption to avoid cold joints.
    6. Concrete shall be properly graded and self-compacting.
    7. Care shall be taken to avoid segregation or contamination of concrete.
    8. Concrete placing rate shall not be less than 6 m pile length per hour.
    9. Temporary casing during concreting shall conform to Clause 1107.3 of MoRTH Specifications.
    10. Where concrete is placed in dry boreholes with casing, top 3 m concrete shall be compacted using internal vibrators.

    9. Mixing, Transportation, Placing & Compaction of Concrete

    9.1 Concrete Mixing

    Concrete shall be produced in approved batching and mixing plants as per Clause 1708 of MoRTH Specifications.

    • Batching plant calibration shall be approved by the AE.
    • Mixing time shall ensure uniform color and consistency.
    • Mixers not used for more than 30 minutes shall be cleaned before reuse.
    • Water-cement ratio shall be maintained considering aggregate moisture content.
    • Approved superplasticizers conforming to Section 1012 shall be used where required.

    9.2 Transportation of Concrete

    Concrete shall be transported using transit mixers.

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    • Concrete pouring shall be avoided during extreme summer and winter temperatures.
    • Concrete temperature during placement shall remain between 5°C and 40°C.
    • Concreting shall not be carried out when ambient temperature exceeds 40°C.

    9.3 Placing & Compaction

    • Concrete shall be placed as near as possible to final position.
    • Concrete shall not be dropped freely from height exceeding 1.5 m.
    • Concrete shall be placed in layers of maximum 300 mm compacted thickness.
    • Fresh concrete shall not be placed against concrete older than 30 minutes without proper construction joints.
    • Formwork and reinforcement shall be cleaned before concreting.

    10. Quality Control

    • Pile Location & Verticality Check
    • Bore Depth Verification
    • Bentonite Slurry Testing
    • Reinforcement Cage Inspection
    • Concrete Slump Test
    • Concrete Cube Testing
    • Tremie Concreting Monitoring
    • Pile Integrity Test (PIT) / Load Test as Applicable
    • Tolerances shall conform to Clause 1116.1 of MoRTH Specifications

    11. Safety

    1. Barricading and warning signage shall be provided around piling locations.
    2. All lifting equipment and machinery shall be inspected before use.
    3. Workers shall use PPE including helmets, safety shoes, reflective jackets, gloves, and safety belts.
    4. Proper illumination shall be provided during night operations.
    5. Safe lifting procedures shall be followed during cage lowering and casing operations.
    6. Emergency rescue arrangements shall be maintained at site during piling operations.