Method Statement -Piling Works

1.0       INTRODUCTION

This Work Method Statement is to outline the installation of drive pile and testing for piling works.

 

2.0       SCOPE OF WORKS

This method statement shall apply for all piling works for (your project name). Details of the procedures contained herein may be modified based upon actual ground condition and site requirements.

 

Material, manpower, plant and equipment as below;

Material                                 : Spun pile 400mm dia. And 600mm dia.

Manpower                            : Piler, welder, operator and general workers.

Plant and equipment         : Hydraulic hammer, pile driver.

 

3.0       RECORDS

Contractor shall submit to the Superintending Officer the piling form format for approval prior to the commencement of piling works.

Contractor shall provide the Superintending Officer with two copies of the records for each pile.

These records shall have the following formation:-

 

a. Drawing Ref No.                                                             i. Length Form Toe to Ground Level  

b. Project Name                                                                  j. Initial Pile Length  

c. Block                                                                                 k. Extension Pile Length  

d. Pile No.                                                                             l. Total no. of extension  

e. Pile Size                                                                            m. Total Pile Length  

f. Type of Hammer & Weight of Hammer                      n. Final Set Per 10 Blows  

g. R. L. of Ground                                                                o. Length of Drop (M)  

h. R. L. of Cut-Off Level; of Driving                                  p. Remarks.  

 

Records of piles shall be made and submitted in the order in which the pile have been driven. Any unexpected driving conditions reported in accordance with, shall be note in the records.

 

4.0       HANDLING OF PILES

Contractor shall exercise the greatest care in the lifting and handling of piles and no pile shall be lifted other than by slinging through the lifting holes. All piles damaged during handling, driving or at any other time shall be replaced at contractor own expense.

 

5.0       PITCHING AND DRIVING

Piles shall be pitched accurately in the positions and driven to the appropriate lines and levels and to a predetermined set as directed by the Superintending Officer. Piles may be suitably constrained to maintain their correct position by means of guys or guides but the piles which has been deflected from its course, or has been incorrectly aligned shall be forcibly brought back to its correct alignment.

Sufficient care shall be exercised in handling and slinging of piles, and no pile shall be lifted other than by slinging from designed and approval lifting points.

Where piles are driven below the level of the bottom of the leads of the pile frame, extension leads shall be fitted.

Before the commencement of driving of each pile, the guides of the pile frame shall be checked for plumb in any two different directions and shall be maintained during driving to the entire satisfaction of the Superintering Officer (S.O.) or his representative. At no time during driving operation shall the center of the hammer or hydraulic ram be more than 50mm off center with respect to the center of pile being driven, in any direction.

Driving of a pile shall, as far as possible, be in continuous operation until the required set is obtained.

For rc square pile, during driving heads of the pile shall be protected by a helmet of cast steel or mild steel fitting closely around the pile. Packing of soiled hemp rope or plywood, 25mm thick, covering the head of the pile, shall be placed within the helmet to separate the helmet from the head of the pile. The top of the helmet shall be recessed and fitted with a timber stub dolly lift 300mm long. The packing a stub dolly shall be renewed as often as necessary to prevent damage to the piles.

For spun pile, when driving commence, the first few blows and meter of penetration shall be closely monitored to enable any initial deviation to be physically corrected. Large deviations in terms of position and inclination (in excess of specified tolerances) shall merit an extraction and re-drive at this stage if forcible corrections are not adequate. For deviations that inevitably occur at deeper penetrations, only measurements in the final set position shall dictate, amongst other factors, the pile acceptance or otherwise. Where driving depths go below the piling rig’s base level, a suitable temporary pile extension of known length and material properties shall be used to enable proper computation of the pile set.

Contractor shall maintain a record of the driving of all piles giving sets and other data required by the Superintending Officer and four copies shall be submitted to the Superintending Officer. All piles shall be driven to the shown on the Drawings or to such final set of depth as may be approved by the Superintending Officer.

The weight, type, height of fall for the hammer and the final set shall be strictly observed by the contractor but under main-con supervision.

The predetermined set must be obtained for three consecutive trails of 10 blows each before driving can be stopped.

 

6.0       BASIC FOR ACCEPTANCE OF INSTALLED PILES

a. The basis for the acceptance of installed piles is that the driving criteria and final set of a driven pile or the design criteria of any other type of installed pile which has been verified by successful load test shall form a basis, on which other piles are to be driven or installed and their performance compared.  

b. Contractor shall ensure that all the other piles are strictly driven or installed to the same conditions or better than the initial tested pile which passes the load test requirements, as any further pile chosen for load test which fails to meet the requirement shall be rejected and all costs for remedial piles and amendments to pile caps shall be borne by the contractor.

c. The pile sections and details have been designed to safely carry the maximum design load as far as the strength of the pile section itself is concerned and subjected to its proper handling. The safe bearing capacity of the pile will depend on the driving criteria adopted and the actual soil conditions and shall have to be verified by an initial load test. Any driving criteria or final set suggested to the contractor by the Superintending Officer shall be fully responsible in all aspects of the design and the contractor only responsible in the aspects of installation of the piles. Contractor shall have the right to adopt a different driving and final set provided their suitability are verified by a load test and also provided the stresses on the pile during driving shall not damage the pile.

 

7.0       HILEY FORMULA FOR PILE DRIVING CALCULATION

For driven piles, calculations are usually based on the Hiley formula, or on one of the many variations of this, designed to give more accurate results or great ease of calculation. The basic formula is:

(Refer to submission of blow count calculation using Hiley Formulae in separate submission).

This formula should only be used when piles are driven into sands, gravels or similar non-cohesive soils or into hard clay or into rock.

The capacity of driven piles is generally a matter of experience on the part of the piling contractor though empirical formula have been devised by many companies. The number of variables and the range of variability are usually too many and too great for even reasonable measurement, but the piling contractor’s estimate of the carrying capacity of one of these own piles is usually fairly accurate.

Temporary compression, C is assumed 14.0mm, fixed value for size of piles. The actual value shall be confirmed after actual set is determined and set calculation shall be recalculated based on actual temporary calculation.

In general, the coefficient of restitution is 0.25 to 0.4 and the hammer coefficient is 0.8 to 0.85.

 

8.0       VERTICALITY OF PILE

For the checking of the verticality of the leader (guide) throughout the driving process, we will use the plumb stand at the side of machine and spirit level. During pitching and installation, the verticality of the pile will be continuously monitored and plumbed to ensure the pile is centrally in line with the pile axis to receive the ram to prevent pile whip, twist or rotation.

 

9.0       PILE JOINTING AND SPLICING

9.1          Pile jointing and splicing

Piles shall be joined at the specified position using the recommended method or propriety systems as required.

Equipment – Welding Set. The type of welding rod are E6013 and size of welding rod shall used 3.2mm and 5.0mm. 

The required setting and hardening times for primers and epoxies, where used, shall be adhered to when pile joints are made, to ensure a safe and effective joint.

The pile will be extended by butt-welding the steel plates on the pile heads. On completion of welding, the slag will be chipped off and wire brushed to receive red-oxide paint.

When welding joints, no gaps shall be allowed and full bearing at the connecting plates between the driven and the extended length shall be ensured. Pile driving will then be resumed after the required setting/hardening times for the weld to develop its strength.

 

 

9.2          Weld Tests

Ø  During production of welded tube piles, at least one radiograph or ultrasonic test approximately 300mm long shall be required on each end of a length as a spot check on weld quality. This shall be taken on a circumferential or longitudinal weld and its position shall be as directed by the S.O.

                                 i.            For tubes of wall thickness 12mm or less, three spot radiographs, one at each end of each length of the tube as manufactured and one at position to be chosen at the time of testing by the S.O; and spot check radiographs as required by the S.O on the weld joints between strip lengths

                                ii.            For tubes of any wall thickness, continuous ultra-sonic examination over the weld, supplemented where necessary by radiographs to investigate defects revealed by the ultrasonic examination.

 

Ø  Weld tests shall be performed by radiographic or ultrasonic methods as specified. Provided that satisfactory result are being obtained, one test of a length of 300mm shall be made 10% or more of the number of welded splices in the case where the load will be carried by the wall or section of the pile will not normally exceed 10%. Results shall be made available to the S.O within 10 days of completion of the tests.

 

9.3          Pile Load Test

 

10.0     PILE CUT-OFF

Piles shall only be cut-off after securing the directive and acceptance by the S.O.  This is to ensure that any re-driving work that would be required can still be carried out when such situations warrant.

The value for pile cut-off level must be formally agreed and any piles that need to be ‘brought up’ to the required cut-off level must meet the S.O.’s agreement and guidelines.

Where pile cut-off levels are below ground, excavation sides shall either be sloped or protected by an earth retaining structure to prevent collapse of the excavated pit.

Where pile cut-off levels are below water level, suitable enclosing structures (e.g. cofferdams) shall be installed to exclude water from the works.

 

11.0     HEALTH, SAFETY & ENVIRONMENT PROGRAMME

11.1     Health & Safety

Ø  Safety induction to be conducted to all new workers that involved to this activity and safety toll box meeting shall be conducted every day to remind the workers about concerning the safety.

Ø  All workers shall be provided with PPE (Personal Protective Equipment) and shall be worn at all time on site. Safety Manager / Safety Supervisor shall ensure all the workers wear all the safety equipment provided

Ø  All workers shall be advised to report any accident or injury to supervisor.

Ø  Proper and adequate provision of temporary signage’s and barricades at diversions and temporary haul road as necessary (if applicable).

 

11.2     Environment

Ø  All workers shall educate on good environmental management practices and well- disciplined to environment.

Ø  The garbage bin shall be provided at the working area and Supervisor shall ensure its must be collected regularly and disposed-off at the approved dumpsite.

Ø  All workers shall ensure that all tools and equipment machinery are in good condition to avoid any oil leakage that could harm to environment.