Combined Static and Push-Pull Injection Concept

This PT350 injects concrete or steel piles using combined static and push pull injection (CSPPI) concept without huge dead weights. It can be easily re-asseamble inside a small footprint of 3.3m x 3.3m that is otherwise inaccesible to large pilling machine. Specially adapted to drive piles in close proximity to wall and confined buildings lots. The piles are injected up to 30m with excellent vertically without vibrations and noise.

 

Methodology of the CSPPI technology

In addition to the machine weight, the principle of the CSPP engages the frictional resistances of the injected piles to assist the pile drive. The piles in the injectors are driven cyclonically by advancing the hydraulic jacks one at time. However, not all the pile will experience the same resistance at similar depths. The piles are driven to a “set” criteria not exceeding the recommend maximum rate of pile settlement of 2mm after duration of 5mins under maintained load of 2.3 to 2.5 times of the working load. The CSPP works best with more than 4 pilling injectors otherwise more kentledge will be required in hard and swallow ground strata. To prevent the precast prestressed concrete pile from tensile cracks, the CSPP pile clamping technology is preset to limit the maximum pile tension exceeding which the clamp will slips.

 

Patented Clamping System

CSPP’s unique patented side-griping pile clamp is free to rotate to a certain degree. Thus, when the pile is injected through an uneven hard stratum, a 2deg deviation along the axes of the pile can be tolerated. This slanted pile will subsequently self realigned to the axis of the pile injector leading to excellent vertically of the driven pile.

 

The pile within the clamped zone mimicks a tightly squeezed egg. The lateral normal pressures on the pile increase in tandem with the vertical injection load leading to a more balanced 3D-uniaxial normal stress in the clamped zone.

The freshly casted 250mm spun piles were injected after 7days using the PT350 to a MAXIMUM load of 180t (i.e 85% of the 28 days characteristics concrete compressive strength of the grade 80MPa}. Despite this extremely hard driving, only about 2% of the total pile driven failed by cracking at the base of the clamps at above the ground level. These piles were later cut well below the damaged portions and tested to 110t with excellent inelastic re-bounce of <2mm. Whereas, using the conventional hydraulic static piling machine to drive the same 250mm spun piles at 110t, it resulted in 15% breakages of the driven piles at 3-8m below ground. Additional piles were required to compensate forevery breakages below the ground.

CSPP drives pile into ground truly vertically due to the inbuilt pile/clamp self-correcting plump mechanisms. The piles in a group can easily be injected vertically with a pile deviation tolerence of <20mm.

Maintained load test using injected pile