Prefabricated House Piles

Prefabricated house piles, mainly consisting of pre-cast piles, are characterized by high bearing capacity and fast construction speed. The following provides an introduction from the aspects of types, construction methods, and manufacturing requirements:

Types

The main types include solid concrete square piles, prestressed concrete pipe piles, and steel piles. Among them, prestressed concrete pipe piles are hollow cylindrical slender precast concrete members manufactured using the pre-tensioning prestressing process and centrifugal forming method. They mainly consist of a cylindrical pile body, end plates, and steel collars.

Construction Methods

These methods include hammering, static pile pressing, and vibration. The construction process involves pile driver positioning, pile lifting and stabilization, pile driving and jointing, etc. During construction, the verticality deviation should be controlled to be ≤ 0.5%, and the pile spacing should be maintained at ≥ 3 times the pile diameter. Taking the construction of prefabricated house piles in rural areas of South Korea as an example, first, install anchor plates on the foundation after the concrete has set. Drill holes with a drill and secure them with expansion screws. After installing anchor plates in six directions, install the prefabricated foundation piles. Then, install the crossbeams, adjust them horizontally, and secure them with nuts. Finally, fill the gaps with expanding foam and seal the nut fixation points with cement.

Manufacturing Requirements

• On-site Prefabrication: Tool-type wooden or steel molds are commonly used, supported on a solid and level floor. The molds should be flat, reliable, and dimensionally accurate. Production is carried out using the interval overlapping method. The pile head is blocked with a steel mold end plate, and the piles are separated with a release agent. The concrete for adjacent piles and upper-layer piles must be poured after the concrete of the adjacent or lower-layer piles has reached 30% of the design strength. The number of overlapping layers should generally not exceed four.
• Reinforcement Requirements: The reinforcement in the piles should strictly ensure correct positioning, with the pile tip aligned with the longitudinal axis. The main reinforcement in the reinforcement cage should preferably be connected by butt welding or arc welding. The number of main reinforcement joints configured in the same cross-section should not exceed 50%. The distance between the cross-sections of adjacent main reinforcement joints should be no more than 35 times the diameter of the main reinforcement and no less than 500 mm. There should be no joints within 1 m of the pile top.
• Concrete Requirements: The concrete strength grade should be no less than C30. Coarse aggregates should be 5 - 40 mm crushed stone or gravel. The concrete should be mechanically mixed, with a slump of no more than 6 cm. Concrete pouring should be carried out continuously from the pile top to the pile tip without interruption and carefully compacted with a vibrator.