The difference between cast-in-place piles and precast piles

Piles can be divided into precast piles (prestressed pipe piles) and cast-in-place piles (bored cast-in-place piles) according to different construction methods. Both are widely used in soft soil and thick buried foundations. They have the characteristics of high bearing capacity, good stability, small settlement, and less consumables. They can effectively meet the requirements of buildings for foundation strength, deformation and stability. The two types of piles have their own characteristics.

Definition

Cast-in-place piles are piles that are formed by drilling a pile hole (or manually digging a hole) at the construction site using a drilling machine, pouring concrete in the hole (or hanging a steel cage in the hole first), and waiting for the concrete to solidify and harden. This type of pile has a high bearing capacity and good stability, and is widely used in various construction projects.

Precast piles refer to piles with a certain length, cross-sectional dimensions and reinforcement that are manufactured in a factory or construction site according to design requirements and then sunk into the foundation using pile driving equipment.

Advantages

Cast-in-place piles

- Strong adaptability: cast-in-place piles can adapt to changes in various strata, including complex geological conditions, such as clay, silt, sand, fill, crushed (gravel) stone soil and weathered rock below the groundwater level. Since long piles can meet the bearing capacity requirements under various geological conditions by adjusting the pile length, they are highly adaptable.

- Flexible construction: cast-in-place piles can be constructed in various complex environments, without the need for prefabrication sites, and concrete can be directly poured after the holes are formed on site, making the construction flexible and convenient.

- Relatively low cost: Since the production equipment and technology of cast-in-place piles are relatively mature, and no large amount of steel is required for prefabrication, their cost is lower than that of prefabricated piles.

- Fast construction speed: The construction speed of cast-in-place piles is relatively fast, especially the rotary mud wall bored cast-in-place piles and rotary mud wall bored cast-in-place piles with mechanized operations, which can complete the pouring of piles and the arrangement of steel bars at one time, improving construction efficiency.

- Environmental advantages: The vibration and noise generated by cast-in-place piles during construction are relatively small, and the impact on the surrounding environment is small, which meets the environmental protection requirements of modern buildings.

Precast piles

- Stable and reliable quality: Precast piles are produced in the factory with stable and reliable quality. Through strict quality control process, the quality of the pile body can be ensured to meet the design requirements.

- Strong bearing capacity: The concrete of the precast pile body is high in strength and has reasonable reinforcement. It can withstand large loads and improve the bearing capacity of the foundation.

- Convenient construction: Precast piles are easy to construct. You only need to transport the precast pile body to the site and sink it into the foundation by driving or pressing it. There is no need to pour concrete on site, which simplifies the construction process.

- Fast construction speed: The construction speed of precast piles is fast, and the driving of piles and the connection of steel bars can be completed at one time, which improves construction efficiency and shortens the construction period.

- Wide range of applications: Precast piles are suitable for bearing capacity requirements under various geological conditions, and can adapt to various types of buildings, such as high-rise buildings, bridges, docks, etc.

Disadvantages

Cast-in-place piles

- Difficulty in quality control: Cast-in-place piles are concealed projects, and their pile quality is affected by many factors, such as on-site pouring quality, mixture quality, pile top connection quality, etc., so quality control is difficult. If the construction management is not perfect or an emergency occurs, it is easy to cause quality problems, such as broken piles, concrete segregation, necking, loose soil at the bottom of the hole or too thick sediment.

- Difficulty in construction: Cast-in-place piles need to be poured and vibrated on site, and the construction environment is not easy to control, especially when underground and underwater construction, there are many construction processes, complex processes, high technical standards, and construction is difficult. If the construction management is not good, it is easy to cause quality problems.

- Environmental protection issues: Cast-in-place piles may generate a large amount of mud garbage during construction, which is difficult to handle and has high environmental protection requirements. If handled improperly, it may cause pollution to the surrounding environment.

- Costs may rise: Although cast-in-place piles are less expensive than precast piles, costs may rise if quality problems cause rework or additional reinforcement measures are required.

Precast piles

- High cost: Precast piles need to be produced in factories, which requires special equipment and technology, so the cost is relatively high. In particular, the reinforcement of precast piles is designed to resist the stress during handling, lifting and hammering, which far exceeds the requirements of normal working loads. The large amount of steel used further increases the cost.

- Limited scope of application: The length of precast piles is limited and is not suitable for deeper underground projects. At the same time, due to the large volume and weight of precast piles, special equipment and technology are required for transportation and installation, which also limits its scope of application.

- Construction noise and vibration: Precast piles are generally sunk by hammering or vibration. The construction noise is loud and the vibration is strong, which may have a certain impact on the surrounding environment. Especially when constructing in densely populated areas such as cities, noise reduction and shock reduction measures need to be taken.

- Sensitive to geological conditions: The sinking effect of precast piles is greatly affected by geological conditions. When sinking piles in hard soil or rock layers, greater resistance may be encountered, resulting in difficulty in sinking piles or damage to the pile body.

Applications

Cast-in-place piles

- Geological conditions:

Cast-in-place piles are suitable for various geological conditions, including soft soil, clay, sand, gravel soil, rock formations, etc. It is not limited by stratum changes and can flexibly adapt to various complex geological environments.

In particular, for foundations where quicksand or pressurized water may occur, cast-in-place piles can also ensure the safety and quality of construction by adopting appropriate construction techniques (such as mud wall protection method).

- Building type:

Cast-in-place piles are widely used in high-rise buildings, bridges, docks, large industrial plants and other buildings that need to bear large loads or have special foundation requirements.

It is also suitable for urban areas with dense buildings, because cast-in-place piles have no vibration and no soil extrusion during construction, and have little impact on the surrounding environment.

- Construction conditions:

The construction of cast-in-place piles is not limited by the site and can be carried out in a smaller space. At the same time, it can realize the simultaneous construction of multiple piles and improve construction efficiency.

Precast piles

- Geological conditions:

Precast piles are mainly suitable for foundations with soft or medium hardness, such as soft soil, sandy soil, plastic soil, silt, etc. It has limited penetration ability for hard interlayers such as thick sand, so auxiliary measures such as lead holes may be required when the stratum changes greatly or there are hard rock layers.

- Building type:

Precast piles are suitable for projects with tight construction period requirements and high construction quality requirements. It is widely used in residential, commercial buildings, infrastructure projects and other fields.

Precast piles have obvious advantages in some projects that require rapid construction due to the high degree of standardization of their production and construction.

- Construction conditions:

The construction of precast piles requires a larger site to place and transport precast piles, and special construction machinery (such as pile drivers) is required for construction. Therefore, the application of precast piles may be limited under limited construction conditions (such as small site, inaccessible machinery, etc.).

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