1. Basic knowledge of pile foundation

（1） Pile foundation

Pile foundation is the most commonly used foundation form among deep foundations. It consists of several piles sunk into the soil and a cap or cap beam connecting the tops of the piles.

（2）The function of piles

The function of the pile is to transfer the load of the upper building to the deeper soil layer with a stronger bearing capacity or to compact the weak soil layer to improve the bearing capacity and compactness of the foundation soil.

（3）Classification of piles

Classification according to stress conditions

End-bearing piles: They are piles that pass through soft soil layers and reach hard soil layers or rock layers. The rock layer's resistance mainly bears the upper structure's load; during construction, the penetration is mainly controlled, and the pile tip enters the depth of the bearing layer or the pile tip. The elevation can be used as a reference.

Friction pile: completely set in the soft soil layer, and the weak soil layer is compacted to improve the compactness and bearing capacity of the soil. The load of the superstructure is borne by the resistance of the pile tip and the friction resistance between the side of the pile body and the foundation soil. , during construction, the design elevation of the pile tip is mainly controlled, and the penetration can be used as a reference.

Classification by construction method

Prefabricated piles: According to the method of sinking into the soil, they can be divided into driven piles, water-driven piles, vibration piles, and static pressure piles.

Cast-in-place pile: A hole is drilled at the pile location, a steel frame is placed, and concrete is poured into the pile. Cast-in-place piles are divided into bored piles, excavated cast-in-place piles, punched cast-in-place piles, sunken tube cast-in-place piles, etc.