The purpose of this Method Statement is to define the procedure for the cutting of piles to the approved cut off level. General sequence of work may include:
- Auger fitted with appropriate head
- Auger drilled into ground to required depth.
- Steel reinforcement cage lowered in the bore hole, with the upper lap length enclosed in PVC sleeve and sealed with sealant to ensure no bond between the reinforcement and the concrete above the pile cut-off level.
- Concrete poured down bore hole
- Wet concrete over spill at ground level
- Ground level excavated and top section of pile ‘broken down’ to desired level
- Pile cap or capping beam constructed
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Following tools and equipment shall be arranged before the start of pile cutting works
- Earth moving Equipment
- Grinders & Breakers
- Jack Hammers & Air Compressor
- Hand tools
Excavation and marking of levels
The area around the piles shall be cleared of any material or equipment stored there. To avoid over excavation, the Surveyor shall check the levels prior to the start of excavation to determine the depth of the required excavation.
Earth moving equipment shall be employed to move the excavated to the designated location in accordance to the type of material removed. The surveyor shall monitor the levels. As the excavation level approaches the cut-off level mechanical excavators shall be replaced by manual excavation.
Pile Cut-off Level Marking
The exposed pile shall be cleaned off and inspected by the Site Engineers of piling subcontractor and contractor for any obvious visual defects.
If the pile is found in good condition, the Surveyor shall mark the cut-off level. The site execution team shall cut using grinders a ring at this cut off level. To prevent any damage to the pile at the cut off level, a second ring shall be cut 70 mm above the first. The second ring shall act as a marker for the cutting by jack hammers to stop. The last 70 mm shall be removed using only light breakers.
Method 1: Pile Cutting by Jack hammers
Jack Hammers shall be employed to cut the piles up to 70 mm above the pile cut off level.
Breakers and power tools shall be employed to remove the rest of the concrete up the cut off level.
Reinforcement Cutting & Protection: The pile reinforcement shall be cut off leaving 1000 mm steel for lapping. The spiral ring reinforcement shall be cut at the concrete cut off level.
Method 2: Taets Hydraulic Pile Breaker
The Taets system from the Netherlands replaces hand-held pneumatic breaking with a large scale hydraulic breaker.
The breaker is suspended from an excavator and makes a horizontal fracture in the pile at cut off level.
Each hydraulic cylinder drives a chisel into the concrete producing a horizontal fracture as the breaking force built up this way always seeks the shortest way through the pile concrete.
This stage takes about 25 seconds. The steel chisels do not have to penetrate beyond the reinforcement bars.
After the fracture is made, the chisels penetrate further into the concrete (usually 25-40 mm).
Due to the shape of the chisel, in combination with the reaction forces on the concrete by the steel reinforcement, the concrete breaks into pieces and can removed without the need for further breaking.
Method 3: Elliot Pile Breaking Method
This technique involves the removal of the unwanted pile section in one piece, exploiting the physics of crack propagation
| Sr. No. | Description of step | Image explanation |
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1 |
Steel reinforcement above the final cut-off level is prevented from bonding with the concrete by fixing isolating sleeves to the bars before the cages are lowered into position. |  |
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2 |
When the pile is finally exposed a 51 mm diameter hole is drilled horizontally into the concrete at cut-off level to just beyond the centre of the pile. |  |
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3 |
A standard hydraulic splitter is inserted and activated and after around 30 seconds the concrete cracks across the desired level. |  |
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4 |
Then an excavator is used to lift off the surplus in a single piece via a lifting eye cast into the top surface. |  |
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5 |
A clear cut pile is available for further works or repairs if required. |  |
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