Casing hole cast-in-place pile

Also known as driven casing pile, involves the use of a steel pipe (casing) that matches the designed dimensions of the pile. After fitting the pipe with a pile tip, it is driven into the soil. Reinforcement cages are then lowered into the casing, and concrete is poured in while vibrating or hammering the casing out. The vibration during the extraction process helps compact the concrete, forming the desired cast-in-place pile. This construction method is suitable for conditions with groundwater, quicksand, and silt. Depending on the method of pipe sinking and the type of vibration during extraction, driven casing piles can be further classified as hammer-driven casing piles, commonly used in cohesive soil, silt, sand, and artificial fill, and vibratory casing piles, suitable for slightly dense to medium dense gravel soil as well.

There are distinct differences between the sinking pipe pile and the bored pile with casing protection.

The sinking pipe pile uses a casing to squeeze out the soil at the pile location. Once the casing is sunk to the designed depth, the reinforcement cage is lowered, and the hole is filled with concrete.

On the other hand, the bored pile with casing protection is a type of bored pile construction. It involves the continuous striking of the pile location with an impact drill to break and extract stones, forming the pile hole. Once the designed pile depth is reached, the reinforcement cage is

lowered, and concrete is poured.

Other key differences include:

The sinking pipe pile avoids issues such as pile body settlement and insufficient bearing capacity caused by floating soil at the pile tip, commonly seen in bored piles. It also effectively improves the surface floating slurry phenomenon of the pile body and saves material. However, it can be challenging to control the construction quality. Rapid pipe extraction can lead to necking of the pile body. Additionally, as an earth-displacement pile, previously cast piles can be affected by soil displacement, resulting in tilting, cracking, or even misalignment.

Due to the significant noise generated by hammering and the vibration impact on surrounding structures, this technique is not suitable for urban areas, and some cities have banned its use in urban settings. This technique is well-suited for areas with loose soil and complex geological conditions. However, it cannot be implemented in the presence of large boulders in the soil layer, necessitating the use of alternative techniques.

There are differences between the rotary drilling pile and the long-spiral drilling pressure grouting pile, primarily in the machinery used and construction techniques. The long-spiral drilling pile is limited to diameters of up to 800mm, while larger diameters require the use of rotary drilling piles.

Fundamentally, both techniques involve mechanical drilling to create the pile hole. Rotary drilling uses a rotating drill, while long-spiral drilling utilizes a long-spiral drilling machine.

Cast-in-place piles refer to piles formed by mechanical drilling, steel pipe extrusion, or manual excavation in the foundation soil, followed by the placement of reinforcement cages and the pouring of concrete. Depending on the method of hole formation, cast-in-place piles can be further classified as sinking pipe piles, bored piles, and dug piles.

The main difference between the sinking pipe pile and the bored pile lies in the presence of a casing during the sinking process for the former. Concrete is poured within the casing, whereas for the bored pile, concrete is poured directly into the drilled hole without a casing.