Method Statement of Bored Piles

What is Method Statement for Bored Piles?

Method statement of bored piles is a construction procedure that includes hole boring into the ground, installing steel reinforcement, casting with concrete to form a pile, etc. Bored piles are constructed in the ground by boring in the circular shape of designed diameters to transfer load from the superstructure into the ground through friction and end bearing.

Other items involved in the method statement

• Description of bored piling works and project name
• References to the executed piling methodology
• Responsibilities of the personnel involve
• Duration, Phasing with the Subcontractors
• List of Subcontractors
• Resources, Equipment, Tools, and Materials used
• Site Planning
• Risk Assessment and Job Hazard Analysis involve in Bored Piling
• Permit and Licensing Requirements
• Supervision and Monitoring Arrangements
• The Methodology of Piling Works
  Process includes:
• Setting Out / Survey of Pile Position
• Setup of Starter Casing
• Drilling
• Installations of reinforcement cages
• Verticality Measurement / Verticality Control
• Cleaning of Pile Toe
• Drilled shaft stabilization
• Pouring of Pile Concrete
• Chipping of Pile Head
• Post-installation testing

Structured Method Statement of Bored Piles

I. Description of Works

1. Introduction

This Method Statement defines the sequence and describes the control procedures to be followed for the Construction of Bored Piles.

In the course of the method statement, the construction of cased bored piles with a diameter of 1200 mm and pile lengths ranging from 15.1 m to 33.6 m is described in detail.

The scope comprises:
Construction of Soldier Piles including Drilling, Installation of Reinforcement Cages, and Pouring of Concrete

2. Definitions

CM: Construction Manager
QC: Quality Control
HSE: Health Safety & Environment
PPE: Personal Protective Equipment
PMV: Plants, Machinery & Vehicles
GIS: Geographical Information System

3. References

Information sources may include, but not be limited to, verbal or written and
graphical instructions, signage, work schedules/ drawings/specifications, work
bulletins, charts, and hand sketches, and Material Safety Data Sheets (MSDS).
Excavation Specification, (Reference goes here)
Concreting Specification, (Reference goes here)
Project Specifications
Baseline Program, (Reference goes here)
Construction Environmental Management Plan, (Reference goes here)
Concrete Mix Design (C50/60 OPC 70%+PFA 25%+MS 5%), (Reference goes here)
Grout Mix Design for Shoring, (Reference goes here)
Polymer, Bentonite & Soda Ash, (Reference goes here)
Steel Reinforcement, (Reference goes here)
General Lifting Plan, (Reference goes here)
Specification for Carbon Steel Bars for the Reinforcement of Concrete, BS 4449-2005
Geotechnical Interpretative Report, (Reference goes here)
Calibration Certificates for Survey Equipment, (Reference goes here)
Shop drawings: (Reference goes here)
Material References:
Bonding Agent (Reference goes here)
Method Statement for Slope Protection Measures (Drop Chain Link, Rock Bolting & Shotcrete)
Polymer, Bentonite & Soda Ash
Monitoring Instruments
Galvanized Pipe for Inclinometer
Galvanized Pipe for Crosshole
Sonic Logging
Plastic Spacer
Document References:
Monitoring Plan References (Reference goes here)
GIR Reference (Reference goes here)
Slope Inspection and Surface (Reference goes here)
Protection Procedure (Reference goes here)
Plot Limits Setting Out (Reference goes here)
Installation of Inclinometer in Pile and Borehole and Type of Inclinometer (Reference goes here)

This might interest you: Method Statement for Civil Engineering

4. Responsibilities

Project Manager
Responsible for accomplishing the stated project objectives which include creating clear and attainable project objectives, building the project requirements, and managing the constraints of the project management triangle, which are cost, time, scope, and quality.
Operations Manager
Overseeing and having responsibility for all the activities which contribute to the effective work products and services. His main role is to understand strategic objectives, develop an operations strategy, design the operation’s services and processes, plan and control, and improve the performance of the operation.

Superintendent
Organizes coordinates and supervises the work of the
Foreman, Sub- Foreman, and/or craft employees on construction. Determines work priorities, schedules jobs, and operations, and coordinates work activities within the design area. Exercises control over the rate of construction progress in order to complete the construction project within time limits.

Site Engineer
Supervise operations in accordance with the approved Method Statement, shop drawings, specifications, material submittals, and schedules to achieve the acceptance of the project deliverables.

Site Supervisor
Supervise closely, the activities designated to them and ensure that all instructions and safety procedures are followed and strictly adhered to.

Site Foreman
To liaise with the Site Engineer and Supervisor for the work execution.

QA/QC Manager
Responsible for all aspects related to the Project’s Quality Assurance and Quality Control. QA Manager Prepares the detailed Project Quality Plan and ensures that it is understood,
implemented, and maintained at all levels of the project organization. QC Manager is in charge of the preparation of the Inspection and Test Plan (ITP) and liaising with Third Party Inspectors, Subcontractor Quality Personnel, and Independent Testing Laboratories for quality-related matters.

QA/QC Engineer
Ensure the proper implementation of the Quality system and monitor the overall quality of the work is maintained. Conduct inspection and monitor tests. Determine and report any nonconformance and recommended corrective actions. Ensure that all personnel is aware of the quality requirement.
Training of relevant personnel.
Conduct surveillance and inspection duties at various stages
to ensure compliance with QA/QC Plan.

HSE Manager
Health, safety, and environmental (HSE) managers generally plan, coordinate and implement issues and directives within the organization. They ensure safe environmental working conditions for all employees.

HSE Engineer
Ensure enforcement of safety procedures in accordance with the approved HSE Plan. Will be closely monitoring the site engineer’s strict implementation of the MS and Risk Assessment, the use of proper tools and equipment to maintain safety, certifications of equipment and their adherence to safety regulations, reporting of any unsafe work, or stopping work that does not comply with ES&H procedures. Will advise for Health & Safety requirements and monitor the Hazard controls implemented on site as per the Method Statement /Risk assessment.

Mechanic
Responsible for the repair and maintenance of all mechanical equipment and plants involved in the project execution.

Electrician
Responsible for connecting and testing all electrical contacts and systems during plant assembly. Ensure that all electrical works are in compliance with the Electrical  Standards.

Welder
Responsible for all welding works needed for the work performing a variety of welding functions. Reads and interprets blueprints and machine drawings to determine specific welding requirements.

Equipment Operator
The only authorized person to operate any equipment to be used in the project.

Rigger
The rigger assists in the movement of heavy equipment and loads to be lifted. A rigger setups machinery and secures it in place and signals or verbally directs workers engaged in hoisting and moving loads, in order to ensure the safety of workers and materials.

5. Interfacing with other Operations

Limit and Boundary of Work
Re-routing of existing Temporary Roads
Excavation
Dewatering

6. Duration, Phasing with the Subcontractors

All works associated with the Construction of Bored Piles referred to in this Method
the statement shall be as per Baseline Program.

7. List of Subcontractors

Main Contractor:
xxxxxx
Subcontractors for Piling:
xxxxx

II. Resources

1. Plant and Equipment

Note:
All 3rd Party Certificates shall be inspected prior to commencing the lifting operation.
All machines shall fulfill Project Specifications requirements if required.
Calibration Certificates for Survey Equipment, (Reference goes here)

1.1 Rotary Drill Rig

A hydraulic rotary drilling rig type BG25, BG28, and BG 40 will be deployed.
The rig provides sufficient power to drill the holes of diameter Ø Casing 1200 mm / Drilling Tool 1180 at a depth of 65m. The base carrier, BS 80, is custom-made for the drill rig, allowing high performance together with extraordinary reliability. 

Besides the capability to excavate the deep piles the machine offers various tools for the quality control data for the driver such as depth and verticality control (see also Part V Sec A Part 2 Cl. 2.6 & 2.7) Specific highlights of BAUER BG’s are:
High safety standards
Environmental sustainability, economic
efficiency and performance
Easy to transport and short rigging time

1.2 Rotary Drill Rig

Kelly bars are key components in the execution of boreholes with hydraulic rotary drilling rigs. The Kelly bar consists of 2 – 5 telescopic tubular sections with a system of 6 drive keys and lock recesses, welded onto their outer surfaces. Additional shock absorbers prevent the Kelly bar from damage during the excavation process. 

Kelly bars transfer the torque of the rotary drive and the crowd pressure of the crowd system concurrently to the drilling tool at the bottom of the borehole where the drilling tool will loosen the material by rotation.
A pin system at the bottom of the Kelly bar allows for fast changing of drilling tools.

1.3 Drilling Tools

The drilling tools are loosening the subsoil and capture loosened material. They are equipped with a so-called Kelly box (on top of the tool) and attached to the Kelly pin at the bottom of the Kelly bar by means of a bolted connection.

According to the existing type of soil or rock different tools with different types of teeth are used.

All tools have to be supplied with sufficient teeth. The quality and wear on the teeth have to be checked regularly and teeth have to be replaced if they are worn out or lost to ensure sufficient working progress.

The pictures below provide an overview of some typical drilling tools and their principal
application.

1.4 Casings

Due to the presence of rock directly below the starting level of the drilling a short casing of <10.0 m is required only. In order to penetrate firm soils, rock, or artificial obstacles a casing shoe/starter casing, equipped with a ring of cutting teeth, is attached to the lower end of the casing string. The starter casing will be equipped either with replaceable or weld-on teeth.

1.5 Tremie Pipes

Tremie pipes are used for pouring the concrete. The tremie pipe will be inserted at the center of the pile. A tremie pipe string consists of distinct tremie pipe sections (with individual lengths between 0.5 m – 6.0 m) connected to each other via steel ropes to reach the pile toe. The tremie pipe diameter will be 254 mm.

A starter tremie is located at the bottom of the whole tremie section. At the bottom, a starter tremie will be added to the pipe string. All joints will be provided with seals in order to prevent cement grout losses and to avoid segregation of the concrete.

A concrete pump (instead of the hopper) will be connected on the top of the tremie string to the pouring of concrete. When shortening the tremie pipe it has to be assured that the bottom end of the tremie pipe remains in the fresh concrete by at least 2.0-3.0 m length at any time.

2. WorkForce

3. Light Tools

III. Materials

a. Concrete
Concrete for bored piles shall be composed in accordance with BS EN 1536 “Execution of Special Geotechnical Works – Bored Piles” in order to have:
– a good ability to flow
– the ability to pass reinforcement without segregation
– high resistance to washout and segregation
– a sufficient degree of self-compaction

The final mix design(s) will be tested and shall be approved by the client prior to the commencement of the works on site. Refer to the approved Concrete Mix Design (C50/60 OPC 70%+PFA 25%+MS 5%), (Reference goes here).
The percentage of additives/chemicals to be used may refer to the attached Technical Data Sheet in Appendix E.
Project Requirements
Concrete will be supplied in accordance with applicable standards, specifications, and environmental
and pouring conditions as well as the approved pile design.
– Concrete strength: C50/60 (with fc, k, cylinder = 50 MPa and fc, k, cube = 60 MPa
– Maximum aggregate size: 20 mm
– Concrete supply rate: Average 80 m³/hr.
– Slump range: 200 mm +40mm/-20
– Minimum concrete cover for piles: 75mm according to EN 1536:2010
The sampling and testing of concrete prior to pouring will be in accordance with the approved ITP for Bored Piles.

Trial Mix
Preliminary trial mixes have been executed in order to verify fresh concrete properties in the laboratory. A large-scale trial mix shall be conducted in order to check;
Fresh Concrete on:
– Slump + Flow over complete retarding time
– Bleeding behavior
– Segregation tendency

Hardening / Hardened Concrete on:
– Initial and final setting time
– Compressive Strength (development) 7 and 28 days

b. Reinforcement / Reinforcement Cages
Reinforcement with steel grade and dimensions according to the project specifications will be used for the fabrication of reinforcement cages, where mill certificates for the steel shall be provided by the supplier.

According to the design, reinforcement steel of a steel grade BSt 500 A (with a yield strength of 500 N/mm²) will be used.

The reinforcement cages will be pre-fabricated and delivered to the installation location in accordance with approved construction drawings. The reinforcement cages shall be designed rigid and stable enough to withstand the forces applied while handling and installation. In case too high deformations while cage handling or lifting will occur, the designer shall be consulted and additional stiffening elements added. The type of reinforcement cage to be used at a specific location/section may refer to the approved shop drawing attachment listed in Appendix A.

Concrete spacers shall be used at proper intervals in height and evenly distributed around the entire perimeter of the cage to keep the reinforcement in the center of the borehole and thus to ensure the required concrete cover at all locations (refer to the approved shop drawing).

c. Fly Ash, Sika Intraplast Z, Sikament- 500 and Sika Retarder
The materials which will be used generally may refer to approved Concrete Mix Design (C50/60 OPC 70%+PFA 25%+MS 5%), (Reference goes here).

1. Test Certificates
All Test Certificates for the above materials shall be provided.

IV. Site Planning

All works associated with the Construction of Bored Piles are referred to in this method.
The statement shall be as per the attached Baseline Schedule attached in Appendix H.

1. Preparation

The contractor shall ensure that all gate passes, permits, tools, and materials for safety
precautions, manpower, and equipment are available before the commencement of work.
The Site Team shall make sure that access roads are always clear from any obstruction and sites are always accessible.

2. Site Clearance

Before commencing the work, the area shall be cleared of all debris, materials, or other obstructions.
All necessary MEP clearances shall be obtained prior to starting activity at the site.
Clash Analysis will be done to verify that no utilities will clash with the shoring system.

3. Traffic Management

The Site Team with the assistance of the Safety Officers shall coordinate logistics and materials movement through the site following the direction and road signs displayed on site. The required diversion routes shall be marked on drawings including the required traffic signs.
The Work Permits and Operator Certificates shall be compiled and filed for reference by authorized personnel.
Temporary traffic signs, barriers, and flagmen will be deployed to control traffic flow in accordance with Section 6, Part I, Roadwork Construction and Traffic Management of the HSE Plan.
At the end of each ramp, there will be a transition area to give the driver the opportunity to watch the access roads before joining thereto.

4. Pre-construction Safety Meetings:

The meeting shall be scheduled prior to the beginning of the work and before any Subcontractor starts on the project.
Safety awareness meetings will be conducted every working day morning/every other day to brief the workforce on safety prevention measures. The equipment check for safety shall be recorded/ documented during the daily Safety Awareness Meeting.
Traffic safety will be discussed to emphasize these meetings.
Each worker will be instructed to follow specific safety requirements related to his trade. They will be required to follow installed safety signs, observe barricades and use opens.
Contractor Safety will perform hazard risk analysis by identifying all steps, and hazards identified in those steps, with a focus on the relationship between the work task, the tools, and the work environment. After identifying uncontrolled hazards; the Contractor will take steps to eliminate or reduce them to an acceptable risk level.
General contractual Safety, Health, and Environmental requirements.
Roles of the contractor, subcontractors, authorized representatives, and all project workers.
Accident reporting requirements.
Specific details of the work to be performed along with the use of personal protective equipment.
Emergency procedure.

5. Operating Procedures:

A site investigation has to be carried out to develop safety precautions and measures prior to the commencement of the work. After such investigation, relevant sign boards will be displayed and barricades will be installed where and as necessary, such as but not limited to the following:
Advanced signs e.g. “Work Area” signs will be placed ahead approximately 300m before the activity zones on both sides of the road.
Relevant information, warning, and mandatory signs such as Narrow Road Signs, One-Lane Traffic signs, etc. will be placed approximately 25m from the last advanced signs.
“One Way traffic ahead” signboards would be placed 90 m ahead of the working area in order to notify oncoming drivers of the new road layout.
Traffic Controllers would be deployed on both sides in order to control “One-way traffic”.
Photographs would be taken for information to maintain traffic safety record-keeping.
A Radio Communication system would be used where normal communication is impossible.
After completion of the work, safety cones and barricades have to be removed accordingly.

V. Methodology

A. Bored Piles Construction

1. Scope

The selection of the technique depends on the prevailing soil conditions, the pile diameter, the pile depth, and the technical specifications (Execution of Special Geotechnical Works-Bored Piles, Ref.: EN 1536:2010). The piles will be executed by the use of a hydraulic rotary drilling rig type BG25, BG28, and BG40 equipped with a telescopic Kelly Bar of a length of 65 m. The soil conditions require a casing of a length of approx. 10 m.
The pile construction shall be done as per the approved Shop Drawing.
The scope comprises:
A. Mobilization of Staff and Equipment to the Site
B. Setup of Equipment on Site
C. Construction of Pile Bores including Drilling, Installation of Reinforcement Cages, and Pouring of Concrete
D. Supply of Reinforcement Cages and Concrete
E. Disassembly and Demobilization of Equipment from Site

2. Construction Sequence

A. Casing Installation with the Rotary Drive of the Drill Rig (Pushing and Rotation).
B. Drilling with Bucket, Auger, or Core Barrel. Stabilization of the wall of the bore partially with casings.
C. Installation of reinforcement cage with the auxiliary winch of the drill rig (or alternatively with a separate service crane) into the borehole.
D. Concrete pour via Tremie Method. The required top of concrete (calculated as per the top level of casing given by the surveyor) will be monitored using an end-weighted scale. The quantity of concrete may be increased in order to fill the space created by the insertion of the casing.
E. Extract Casing with the Rotary Drive. The extraction will be done by rotating the casing gradually in a clockwise and counterclockwise direction until the casing has been completely removed. The casing can be removed once the concreting has been completed.

2.1 Working Platforms and Ramps

The piling platform, access ramps, and additional storage/working areas are to be constructed in accordance with FPS and BRE guidelines.
The work areas shall consist of suitable granular/non-cohesive material, well compacted and constructed in a leveled manner. The design of the working platform shall allow safe movements of and safe working conditions for a 97-ton drilling rig(s) and associated service equipment during all weather conditions.
At the general top of any working, the platform should be at least 2.0 m above ground water level and inclination must not exceed 1%. The inclination of access ramps shall not exceed 10%.
More specific information about the weights and pressures imposed by the drilling rig can be provided upon request.
Once the platform is completed and all plant is mobilized, a permit to dig will be issued by the main contractor prior to the commencement of drilling any piles. The location of all utilities shall be confirmed and highlighted/identified both on the permit and on the site. Any utilities that may be affected by our works that cannot be redirected, or removed, shall be protected as required.
For safety reasons and to ensure an unimpeded sequence of work the entire piling platform has to be finalized and handed over to Bauer prior to the commencement of piling operations.

2.2 Setting Out / Survey of Pile Position

The center of individual pile locations will be set out accurately by a surveyor using suitable surveying techniques. The pile center will be clearly marked using steel pins (or similar), approximately 15mm in diameter and long enough to be stable in the ground.
All setting out and survey works shall be done in a timely manner, not obstructing the work sequence and progress. Survey records/protocols shall be prepared by the surveyor and shall be in accordance with the approved shop drawing.

2.3 Positioning of Drill Rig

Prior to the positioning of the drill rig the pile center will be backed up by 2-3 nos., steel reference pins 600mm equidistant to the pile center parallel to the guide wall. The casing with a 1200 mm diameter shall be installed to the pile center through the guide wall and the two reference points parallel to the guide wall. The operator of the BG rig will bring the casing into the exact position with the help of these reference pins.

2.4 Setup of Starter Casing

Before rotating the casing into the ground by the high torque of the rotary drive of the BG the mast and the casing shall be adjusted to the vertical position. The mast inclination will be monitored via the onboard control system (B-Tronic) of the drill rig.
The achievement of high precision in verticality requires accurate insertion of the starter casing. The starter is guidance for the complete bore and therefore determines the overall pile verticality. For this reason, the verticality of the starter casing will be checked for every 1m insertion of the casing in two perpendicular locations and adjusted in two directions by means of the precise spirit level.
Depending on the soil conditions either a single wall casing with the required length or a segmental starter casing will be inserted into the ground. After this first insertion of the casing, excavation with appropriate drilling tools (e. g. auger or bucket) is carried out until the excavation inside the casing has reached approximately 1.0 m above the lower end of the starter casing, while the casing will be concurrently inserted into the ground.

2.5 Cased Drilling

The progression of the casing is achieved via rotation and the application of a pull-down force which is transferred via the rotary drive or a hydraulic casing oscillator.
The cased drilling will be stopped once approx. 9.0 m of casing will be installed into the ground and drilling will be continued below the casing with the drilling tool(s) only, i.e. uncased.
BAUER or equivalent drilling rigs are equipped with a telescopic Kelly bar where drilling tools are attached to it at the lower end. The tools are adapted to suit the ground conditions.
The excavation of materials inside the bore will be performed via a combined rotation of the pull-down force applied to the tool. Once the tool will be filled with the material it will be withdrawn from the bore with the Kelly bar above ground where the tool(s) will be emptied aside from the bore. If any cavities are encountered, the borehole will be backfilled with lean concrete prior to re-drilling. The drill spoil will be emptied directly on the working platform. From there the drill spoil has to be loaded concurrently with the drilling by means of an excavator or wheel loader and removed from the site.

2.6 Verticality Measurement / Verticality Control

Bauer or equivalent Rigs are equipped with a built-in Inclinometer where the operator can see information about the inclination of the boom immediately on a screen. This information allows the operator to immediately counteract borehole deviations while boring operations.

2.7 Cleaning of Pile Toe

The pile base of foundation piles shall be cleaned according to applicable Standards and the Technical Specifications of the project. Several methods can be used to remove loose materials and sediments from the pile toe in order to achieve a proper interface between pile concrete and the subsoil, thus mitigating later settlements of the foundation pile.
All boreholes are cleaned mechanically using a cleaning bucket with a cleaning edge. Cleaning buckets can be used in dry and wet conditions. The cleaning bucket removes debris and fines from the pile base and fines. There will be no boreholes left uncovered/unprotected at any time. It will be covered by means of a metal pile cover.

2.8 Installation of Reinforcement

Shortly before the installation of the reinforcement cage, the depth of the pile bore shall be rechecked with a measuring tape and connected drop weight.
After the borehole and the pile base are approved by the Client, the reinforcement cage will be lifted using a lifting beam and lowered into the borehole via a crawler crane. The approval has to take place in a timely manner, not obstructing the piling sequence or progress.

A reference site datum level will be given by the surveyor to ensure the correct positioning of the cage.

The reinforcement cage will be lowered down to the required level and the top of the reinforcement will be installed within the tolerances to the approved level at a maximum deviation of 0.15m (as per EN 1536). The correct elevation of the reinforcement cage will be achieved via the suspension of the cage to the casing.

In the case of the reinforcement, cages are too long that they cannot be delivered on-site in one piece and/or too long that they cannot be lifted in a safe manner, several shorter cage sections are manufactured/delivered. These individual cage sections are connected to a single cage by couplers. Commonly the upper cage section(s) are connected to the lower cage section(s) right over the bore. In case the complete reinforcement cage is rigid enough to withstand the forces applied while lifting, it might be decided to connect several single cage sections horizontally on the working platform.

Reinforcement Cage

Concrete spacers as detailed in the approved shop drawing shall be used at 3 m intervals and around the whole perimeter of the cage, 5 nos. each level/layer to keep the reinforcement in the center of the borehole, and thus to ensure proper concrete cover at all locations. As the case may be spacers will be installed to the reinforcing cage concurrently while lowering it down into the bore.

The cage will be trapped off at the top welded band. Once inside the bore the cage has no fall radius. The lifting chains are then changed over to an open hook set and lowered into the bore so that the top of the steel is positioned at the correct level.

2.9 Installation of Tremie Pipe String

Tremie pipes shall be installed centered into the pile bore to the pile toe. The tremie pipes shall be internally free of any old and hardened concrete to allow for a smooth concreting procedure. The tremie pipe will be inserted at the center of the pile. The top of the tremie pipe will be connected to a concrete pump. O-rings have to be inserted into the joints of the tremie pipes to ensure adequate water tightness and thus avoid segregation of the concrete.

2.10 Pouring Concrete

The concrete mix proportions will be in accordance with the approved mix design.
For this reason, delivery notes will be checked for compliance with the mix design and for verification of the installed quantity into the pile bore. The concrete properties and the installation will be monitored in accordance with the Inspection and test plan and to relevant standards.

Concrete will be delivered to the site by mixer trucks and directly discharged into the tremie pipe through the concrete pump. It shall be placed without interruption to prevent the hardening of the previously placed batch.

Pouring of Concrete

While concrete rises inside the bore, the tremie pipe string will be extracted. When shortening the tremie pipe it has to be assured that the bottom end of the tremie pipe remains in the fresh concrete by at least 3.0 m in length at any time. Casings will only be withdrawn to such levels that the concrete level will be still above the toe of the casing.

For measurement of the level of concrete within the pile, an end-weighted measure tape will be used. The concrete will be poured above the final pile cut-off level to ensure proper quality and contamination-free concrete at the pile cut-off level. The excess concrete above the cut-off level will be removed after hardening.

On completion of the concreting operation, the temporary casing will be withdrawn using the piling rig.

No dewatering operation will be carried out in the area of pile casting. The minimum distance between the running well and pile casting shall not exceed 40 m.

2.11 Chipping of Pile Head

After hardening the concrete, the excess concrete is chipped down to the cut-off level as per design. This work can be done by:
Breaking down the concrete with the help of a jackhammer manually or installed on a digger or by the use of a pile head cutter.
Milling of the excess-concrete
To avoid damage to the reinforcement cage in that section, the connection of the bars to the concrete is prevented by the protection of the steel bars.
The chipping activity shall be in compliance with the cut-off levels as per approved shop drawings.

3. Tolerances / Requirements

In accordance with EN 1536:2010 – Execution of Special Geotechnical Works – Bored Piles
Pile Position and Verticality:
The plan position for bored piles at commencing surface will be within 0.05 x d1 with 1.0 m < d1 ≤ 1.5 m = 60 mm in any direction.
The finished pile shall be within the maximum deviation of 10% of the pile diameter. Refer to EN 1536.
The verticality of the piles shall be within 1.0 % in both transverse and longitudinal directions.
Reinforcement Cages:
Reinforcement shall be maintained in its correct position during concreting of the piles within a vertical tolerance of +150/-150 mm on the level of the reinforcement projecting above the final cut-off level.
Setting Out:
Setting out pins shall be placed within a tolerance of 2.5 mm in any direction.

4. Specific Requirements

4.1 Verification of Technical Information

Prior to commencing any operations, technical information such as pile coordinates, platform, and cut-off levels or validity of drawings will be verified to ensure that the pile will be built in accordance with the requirements and design.

4.2 Construction of Borehole

a. Excavation Quality
To achieve the required verticality, the accurate set out of the casing is essential.
During the installation of the starter casing, its verticality is checked several times. The built-in inclinometers in the operator’s cabin allow exact verticality control and the rig operator makes corrections by activating the mast positioning cylinders. Also, the casing itself will be checked manually using a spirit level.

Upon reaching the designed depth and cleaning the pile base, the final depth will be confirmed by a manual measurement with a measuring tape.

The excavated material will be continuously checked to confirm the basic soil assumptions and thus the design premises.

0). After the final depth is reached, the base will be cleaned with a special cleaning bucket. This bucket has no teeth at the bottom.
The base will be checked by the client. Loose material on the bottom which has a negative impact on the bearing capacity may be removed with the cleaning bucket, the air-lift method, or the submersible pump.
b. Check Excavated Soil
The excavated soil will be continuously checked to confirm the soil report. In case of any variation, the construction method and the used drilling tools may be adapted to the new soil conditions, if required.

4.3 Reinforcement

The steel reinforcement will be tested by the supplier and test certificates will be submitted for approval.
The reinforcement cages are manufactured according to the specifications. Prior to installation cages are checked, that:
All rebars are installed and fixed according to the shop drawings and specifications.
All spacers, stiffeners, bands, lifting devices, etc. are installed and fixed according to the drawings and specifications.
All joints of the cage sections are carefully prepared and provide the required lap length.
All starter bars will be protected by using PVC sleeves to eliminate the bonding of concrete and steel during pile head chipping.
The cages have to be centered with spacers.

4.4 Concreting

a. Concrete Testing
It has to be ensured that the delivered concrete is in compliance with the technical specifications and the practical requirements for the pouring process.
Before the actual concreting of a pile starts, slump tests will be made by the supplier to confirm the workability of the concrete.
Test cylinders for drilled shaft concrete in a sequence specified in the contractual documents will be taken at the place of concreting and should be tested after 7 and 28 days.

b. Pouring of Concrete
The concrete will be delivered to the site in ready-mix trucks in accordance with the approved Mix Design enclosed in Appendix G. The concrete quantity shall be sufficient to guarantee a continuous concreting procedure without interruption due to the non-availability of concrete.

The concreting will be performed by pouring the concrete continuously from the concrete pump through the tremie pipe and filling the borehole from bottom to top. To avoid segregation, measures will be taken to minimize excessive contact of fresh concrete with water.

During concreting, the tremie pipe will remain embedded in the fresh concrete by a minimum of 3.0 meters. The total volume of concrete consumed by each pile will be calculated and compared with the theoretical volume in order to identify the quantity of over-consumption. The concreted level will be brought to at least 1000mm above the pile cut-off level to ensure good quality and contamination-free concrete at the pile cut-off level. The surplus concrete part will be chipped/trimmed for the purpose of construction of the capping beam. Trimming will be carried out with a pneumatic or hydraulic breaker.

5. Records

Pile records shall be kept as indicated in the asterisk in Table 1.1 below, of the installation of each pile and shall submit 2 signed copies of these records to the Engineer not later than noon of the next working day after the pile is installed. The signed records will form a record of the work. Any unexpected driving or boring conditions shall be noted briefly in the records.

6. Installation and Monitoring of Inclinometer

Installation and monitoring of inclinometers shall be in accordance with the users’ manual for model EAN-26 Digital Inclinometer System Overview and Installation document no. WI6002.104 Rev.00 and users’ manual for Model EAN-26 Digital Inclinometer System Operation document no. WI6002.103 Rev.01. (Refer to the Inclinometer User Manual)

1. Monitoring Schedule/Sequence

Monitoring schedule or frequency shall be in accordance with § 3.8 pg. 23 of Tender
Specifications S0809-Geotechnical Instrumentation and Monitoring (Supplemental).

2. Preparation of Casing before Installation

In a clean work area near the site of installation, collect all materials to be installed along with required accessories, tools, and consumables. Casing and couplings can be partly preassembled in this area. ABS casings are the self-aligning type.
Note: Pre-assembly and storage of inclinometer casings should always be done in the shade as prolonged exposure to direct sunlight might distort the casings and other ABS parts.
Clean the inside of the weighted bottom cap and the outside of the lower end of a casing with a moist cloth (isopropyl alcohol can be used, if greasy). Push the weighted bottom-end cap over the casing. If the bottom cap is a weighted one, then only 24 pop rivets will be required. For a normal bottom cap, only 4 no. pop rivets are sufficient. Holes for rivets are already drilled on the end cap.

Use a 3.2 mm diameter drill bit to drill holes in the casing. The riveting should be done at
diametrically opposite points 90° apart. Seal joints between the bottom cap and casing with mastic waterproof tape. One round of this tape with a 10 mm overlap is sufficient. Press the tape firmly after applying, it to remove any air pockets. Additionally, wrap three to four rounds of BOPP tape with a little force over the mastic tape for additional protection. Proper sealing is necessary to prevent the intrusion of backfill materials inside the casing.

Further, attach a fixed coupling each to the end of the casings to be installed in the borehole. Clean mating surfaces with a moist cloth (isopropyl alcohol can be used if greasy). Push 160 mm long fixed coupling over the end of the casing up to the maximum allowable depth of around 80 mm. Drill holes with 3.2 mm bit and pop rivet coupling to the casing at four places (the position for two pop rivet holes is marked on the coupling the other two holes should be symmetrically drilled). Seal the joint between the fixed coupling and casing with mastic waterproof tape and BOPP tape. Proper sealing is necessary to prevent the intrusion of grout inside the casing. The casing assemblies are now ready for installation. Carefully transport them to the site, when required.

7. Installation of Inclinometer Casing in Borehole

At the completion of the borehole drilling and sampling, inclinometer pipes shall be lowered within the hole and grouted. The special pipes have 70mm of OD and 58mm ID with a length of 3m. The pipes are connected using the coupling to reach the bottom of the installation intended. The end of the pipes has an end cap. The annulus between the walls of the hole and the pipes is to be grouted using cement: bentonite (4:1 ratio with 125 liters of water). At the completion of grouting, the inner pipes shall be flushed with water in order to make sure no grouting residue has leaked into the installation.
The inclinometer monitoring system will be checked on a calibration check frame periodically.
The lowest 3m. of the installed inclinometer casing, which should be beyond the zone of movement, acts as a calibration check zone for the inclinometer probe. The results of this zone will be a part of each data set recorded.

1. Lower casing with a bottom cap into the borehole gripping it with the safety clamp secured around 500 mm from the top.

2. Take a casing pre-assembled with a fixed coupling, having a safety clamp secured around 500 mm from its top end, and mate it with the pipe already lowered through the coupling end. Pop-rivet the fixed coupling to the lowered casing at four places. Seal joint with mastic waterproof tape and BOPP tape, as described above. Remove the safety clamp from the first casing and lower the jointed casings into the guide pipe/borehole.
NOTE: Always use a safety clamp such that the casing does not accidentally fall into the borehole while installing.

3. Flush lockable covers (250 mm x 250 mm) will be installed by RGS for the protection of instrument tops. It will protect the instruments from damage due to the movement of construction equipment.

4. To counteract buoyancy, if required fill the casing with clean water to lower it into the guide pipe/borehole.

5. Repeat the above procedure for all the casings to be installed in the borehole.
The grout mix to be used will be as follows:
Hard and Medium Soils
Cement 50 kg
Bentonite 15 kg
Water 125 liter
Soft Soil
Cement 50 kg
Bentonite 20 kg
Water 325 liter

6. Flush the inside of the casing with water after grouting. This is to prevent any leaking in the grout from sticking to the casing and impairing the movement of the torpedo.

Figure 2: Inclinometer Installation in Ground- Installation Sequence

7. Top of the uppermost casing should be kept below the final ground level and protected by a top cap and lockable manhole cover. Cut the top of the pipe suitably by a hacksaw. Use the flat file to make the pipe end smooth.
NOTE: The top of the uppermost casing should be 125 mm above the base of the niche as shown in Figure 3 the niche is around 200 mm deep. This is necessary for fixing pipe
extension jig over casing for taking readings.

8. When not taking readings, the gauge well should be protected by the top cap and the manhole cover should be kept locked.

9. Fix the manhole cover in the concrete platform on top of the borehole. Manhole covers feature a universal key and dust protection for the lock (always put back the dust protection after locking to avoid lock jamming). These may vary depending on the local site conditions.
Note: Plying heavy machinery such as cranes, loaded trucks, etc. over the manhole cover should not be allowed and if required proper fencing with warning flags should be
provided.

10. Mark tag no. of the installation in the paint on the inner side of the cover. Also, mark casing grooves as ‘A+’,’A-’,’B+’ and ‘B-’ with the permanent ink marker pen. If the uppermost torpedo wheel is pointed in direction of the major principle plane of movement, the casing groove pointing in this direction is marked as ‘A+’. Looking down the well, directions ‘B+’,’A-’, and ‘B-’ are clockwise from ‘A’.
A. Grooves will be used for the traversing of the inclinometer probe and will always be
aligned perpendicular to the direction of the excavation.
B. Grooves of the casing, which are orthogonal to the A-grooves, will be parallel to the
shaft by default.

11. Before taking the first reading the grout filled in the annular space between the borehole and access casing should have been sufficiently set. The first reading shall be taken at least one week after the grouting.

12. In order to take the readings, a pipe extension jig shall be installed over the pipe top if required, and secure the cable shoulder plate over the former. Lower inclinometer probe to the bottom of gage well with uppermost torpedo wheel pointing in the direction marked ‘A+’. Raise the probe along the entire length of the gage well from bottom to top, taking readings at intervals of 0.5 m. Two sensors located in the probe sense the inclination of the casing in two planes at right angles to each other. Again lower the probe to the bottom of the gage well with the uppermost torpedo wheel pointing in the direction ‘A-’. Raise the probe along the entire length of the gage well from bottom to top, taking readings at intervals of 0.5 m.

13. A set of initial readings shall be taken within the gauge well. The base reading is formed after taking at least three sets of initial readings. Choose the most repeatable reading set and make it the base. All subsequent readings are compared with this base reading thereby indicating the rate, magnitude, and direction of lateral deformation. This inclination is displayed in terms of horizontal displacement on the data logger or smartphone at the ground level with the operator.

14. A survey marker shall also be installed near the top of the installation in order to monitor possible surface deflections if needed. The marker will have x, y, and z coordinates taken.

15. Data of the inclinometer will be reported as a chart between changes in cumulative deflection with the initial value in A+ A- plain (principal plane of movement) v/s depth. Y-axis will show depth in meters and X change in cumulative deflection from the initial in “mm”. A positive deflection will represent movement towards excavation and vice versa. Trigger values (amber, red & black) will be depicted in the graph as vertical lines for easy interpretation. Data on inclinometers will be reported as required by the Client.

8. Installation of Inclinometer Casing in the Pile

The installation of the inclinometer casing in the pile is the same as the installation in the borehole with some differences. A GI pipe (4’’ – 6’’) will be installed in the pile before casting as per Figure 4. After casting off the pile, the inclinometer will be installed in the GI pipe and grouted.

Data Reporting and Interpretation

Data from the inclinometer will be reported as a chart between changes in cumulative deflection with the initial value in A+ A- plain (principal plane of movement) v/s depth. Y-axis will show depth in m and X change in cumulative deflection from initial in mm. A positive deflection will represent movement towards excavation and vice versa. Trigger values (amber, red & black) will be depicted in the graph as vertical lines for easy interpretation. Data of inclinometers will be reported under daily and weekly monitoring reports.

Figure 3: Installation of the Casing in the Pile

VI. Risk Assessment and Job Hazard Analysis

Please refer to the attached document in Appendix B.

VII. Permit and Licensing Requirements

Please refer to the attached “Permit to Work” in Appendix C.

VIII. Drawings, Diagrams, and Maps

Please refer to the attached document in Appendix A.

IX. Pre-Start Safety Briefing Arrangements

Refer to Risk Assessment Appendix B.

1. Protective and Safety Equipment
All workers involved shall be equipped with adequate PPE as stated below:
Safety Helmet with Company Logo
Safety Boots
High Visibility Vest
Safety Goggles
Hand Gloves
Coveralls

2. Information to Personnel

Safety Induction
Job training
Superintendents’ Notices/Memos
Toolbox talks
STARRT Card

3. Special Safety Requirements:

All necessary personal/protective equipment (PPE), as well as harness, be provided.
Banksman, wearing distinctive vests, shall be assigned to help operators maneuver their equipment.
The equipment operators shall possess the required licenses and certificates.
Generated dust shall be controlled by periodic water spraying.
The required TSTI will be prepared prior to the commencement of work and positively implemented.
The project safety officer is responsible along with the project zone site engineer for ensuring that all operations are carried out with due regard to the safety of all project personnel & property.
In the case of working at night, please refer to Method Statement for Night Works (Reference goes here).

4. Emergency Procedures

(Reference goes here)

5. Emergency Contact Numbers

(Reference goes here)

X. Supervision and Monitoring Arrangements

Construction Manager
Overall in charge of Construction activities. Schedule the project in logical steps and budget the time required to meet deadlines. Inspect and review projects to monitor compliance with building and safety codes and other regulations.

Site Engineer
The Site Engineer shall evaluate the number of materials consumed by each trade to be compared against the planned quantity.

Site Foreman
A construction foreman is responsible for supervising the workers and also doing actual construction work. The foreman monitors employees to ensure that the work is done efficiently and within quality standards.

QA/QC Engineer
The QA/QC Engineer shall monitor whether the installation works are conforming to the required quality otherwise he shall notify the Site Engineer should he find non-conformance to the ongoing activities. The Site Engineer shall immediately rectify the work to avoid receipt of NCR from the QA/QC Engineer.

HSE Engineer
The Safety Engineer shall be full-time at the site and shall frequently visit all the ongoing works at the site. All safety violations and on-conformance of the HSE Plan shall be registered and immediate action shall be done in coordination with the Site Engineer.

PMV Engineer
The PMV Engineer shall monitor the proper utilization of all equipment, machinery, vehicles, and plant on the site. Keep records of all equipment, machinery, vehicles, and plant as per Daily Checklist and prepares the preventive maintenance schedule as well.

Chief Surveyor
A Chief Surveyor ensures that surveying data are collected and recorded accurately and that all company procedures are followed by crew members.

XI. Environment and Quality Issues

1. Precautionary Measures

All precautionary measures shall be briefed to all workers prior to commencing the activity.

2. Disposal Requirements

All waste shall be disposed of as per Environmental Compliance and Management Plan,
ref. no.: (Reference goes here).

3. Inspection, Test, and Sampling

a. Request for Inspection and Testing will be submitted prior to and after execution of works. An inspection and Test Plan (ITP) shall be provided.
4. Quality Assurance Requirements Table
Refer to Project Quality Plan
Inspection and Test Plan (ITP) shall be provided.

XII. Attachments

1. Appendices

Appendix A: List, Sketch, and Drawings

1. Shop Drawing List

2. Shoring Layout

3. Grout Plant

4. Anchor Fabrication Area
Appendix B: Risk Assessment
Appendix C: Permit to Work (Excavation Works) & Lifting Permit
Appendix D: Inspection and Test Plan
Appendix E: Materials

1. Technical Data Sheet & Material Safety Data Sheet

2. Test Certificates and Technical Data Sheet

Appendix F: Equipment Data Sheet & Third-Party Certificates
Appendix G: Concrete/Grout Mix Design and Trial Mix Results

1. Concrete

2. Grout

Appendix H: Baseline Programme
Appendix I: Quality Forms
Appendix J: Organizational Chart
Appendix K: Anchor Details
Appendix L: Survey Equipment Calibration Certificate
Appendix M: Rig Stability and Ground Failure Estimation for Working Platforms
Appendix N: Emergency Preparedness
Appendix O: Logistic Plan
Appendix P: Piezometer Layout

tag: # method statement for bored piles

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