How To Do Pile Driving With Percussion Method

Written by Harry Lee Under Pile Driving, Piling

There are several types of pile driving method in the piling construction, type of pile driving method used is depending on the condition of soil and location of the site. However, different piling machine will be used with different pile driving methods too. The specification for pile driving mentioned below is generally recommended for pile driving of prestressed spun concrete piles by using percussion method. Engineers may be required to modify some of the clauses to suit requirements of different site conditions.

How To Do Pile Driving With Percussion Method

1) Joints

The bending strength of a joint between two lengths of pile shall be equal or more than the bending strength of the concrete shaft. When two lengths of pile are jointed, the end plates must bear over their complete areas. The two end plates are then welded along their entire periphery with weld size as specified.

1.1 Welding of Joints
All welding shall be carried out in accordance with the requirements of B.S.5135:1974 – Metal-Arc Welding of carbon and carbon-manganese steel.

1.2 Tests for Approval of Welders
Welders shall be qualified in accordance with the requirementsof AWS Code D1.1. Only welders who pass the qualifying tests for the type of weld specified shall be employed on the Works.

1.3 Examination of Welds
Butt welds between the end plates of the joints shall be tested using magnetic particle or dye penetrant test methods. Copies of these test records and reports shall be furnished to the Engineer.

Where such examination reveals defects in the welds, the joints shall either be rejected or repaired. If repeat tests show the weld to be still defective, the joint shall be rejected. The defective weld shall be removed, replaced with a fresh weld and re-examined.

For the purpose of this Clause, cracks, leaks, laminations, lack of complete fusion, undercutting or reduction in wall thickness adjacent to the weld shall constitute a defect.

2) Pile Driving by Using Percussion Method

2.1 Pile Hammers
Shall be of size and type able to deliver consistently an effective dynamic energy suitable to the piles to be driven and the material into which they are to be driven. Hammers shall be provided with proper driving helmets suited for the piles. Any indication of collapse of hoses, tripping of hose lining or any erratic action of the hammer shall be cause for immediate shutdown until the problem has been corrected.

Pile hammers shall be operated at the full rated efficiency and capacity and in the manner specified by the manufacturer, except as directed otherwise by the Engineer, or noted herein below under Reductiono of Hammer Energy.

When a steam or air hammer is used for driving any type of piles, both the volume and pressure of steam or air recommended by the manufacturer of the hammer shall be maintained at all times to ensure full energy of the driving blows. Before pile driving is started, the Piling Contractors shall provide written certification to the Engineer that the pile hammer, compressors and valves have been inspected and found to be in good working condition.

2.2 Reductiono of Hammer Energy
When the pile is set in a pre-jetted or pre-drilled hole or when the point of a prestressed concrete pile is passing through soft soil so that there is little or no resistance to penetration of the pile, there is a possibility that longitudinal tensile stresses may be set up in the pile shaft by the elastic shock waves travelling up and down the pile. For such driving conditions, the length of stroke of the hammer shall be reduced. Failure of the piles due to longitudinal tensile stresses caused by excessive driving shall be the Contractor’s responsibility.

2.3 Pile Cushion Block
The heads of all prestressed concrete cylinder piles shall be protected with a soft wood cushion block at least 15 cm thick to effectively and uniformly distribute hammer blog energy. The block shall be composed of layers of 20mm hi-grade marine plywood or approved equal, and of such dimensions as to completely cover the concrete cross-section of the pile. The cushion block shall be inspected periodically during driving and no driving shall be done with a block that has been unduly worn and compressed with use. Cushion blocks must be replaced when compressed to 1/2 their original thickness, when badly worn or when burning.

2.4 Driving
The piles shall be driven to the driving resistance or tip elevation as determined by the Engineer from pile load tests. The maximum allowable variation at the butt end of the pile shall be 150mm in any direction from the location shown on the Drawings or as directed by the Engineer. Any variation beyond these limits shall be allowed or rejected at the sole discretion of the Engineer.

3) Cutting Off and Capping Piles

Tops of foundation piles shall be embedded in the concrete footing or pile cap for a minimum depth of 75mm (measured at center line of pile). When the top elevation of a pile is below the elevation of the bottom of the cap, the pile shall, if approved by the Engineer be built up from the butt of the pile to the elevatioon of the bottom of the cap by an approved method. The cuts shall be made accurately in clean, straight lines; care shall be exercised to avoid damaging the remaining pile and to ensure full bearing between the footings (or pilecaps) and piles.

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