Introduction
Mini piles are small diameter piles similar to rock socketed H-piles but the diameter even less. They comprise a buddle of steel reinforcement bars installed inside a grout filled circular hole. The pile diameter ranges from 150mm to 300mm.
Same as rock socketed H-piles, the load bearing capacity of mini piles is derived exclusively from the lateral friction in rock since the end bearing is neglected. Typical mini pile applications include underpinning of existing structures, slope stabilization or upgrading of existing abutments and piers.
General Processes
Mini piles are installed by forming a pre-bored hole in the ground with a socket in rock using light hydraulic drilling rig. A permanent steel casing will be installed to support the unstable strata and ensure safe working conditions on ground / working platform. “Overburden drilling method” (down-the-hole hammer technique) will be adopted for sinking the pre-bored hole. This technique is suitable for variable ground conditions including boulders and hard rocks.
Subsequent to the pre-boring, the following processes will be followed.
- Air-lifting and pile base cleaning,
- Installation of steel reinforcement bars,
- Backfilling the bored hole with non-shrink cement grout by tremie method.
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