Driven precast concrete piles are a popular type of foundation construction method. These piles are made by hammering them into the soil with an adjustable hydraulic or diesel hammer to a depth greater than 40m. They are versatile and can be used in various ground conditions, making them suitable for the foundation of almost all types of engineering structures.
One of the advantages of driven precast concrete piles is their suitability for use in soft deposits and aggressive or contaminated soils. This makes them particularly useful where the founding stratum is overlain by such soil types. The piles are manufactured in factories with high-quality control measures in place. They consist of segmental lengths of reinforced concrete sections with lengths ranging from 3m to 15m and standard or required cross-sections.
Sequence of Precast Concrete Pile Production
Prestressed piles require several important steps in their manufacturing process. The first step is casting, which involves pouring concrete into a mold to form the pile. After casting, tensioning work is done to create prestress in the pile. This involves applying a load to the pile to create tension in the steel reinforcement, which will provide the necessary strength for the pile.
The next step is curing, which is the process of keeping the concrete at a controlled temperature and humidity level to allow it to harden and reach its maximum strength. After curing, the pile is ready for release in the case of pretensioning. This involves detensioning the steel strands to release the prestress, which allows the pile to be removed from the casting bed.
Finishing is the next step, which involves smoothing and shaping the pile to ensure it meets the required specifications. The pile is then marked with the necessary identification information, such as the manufacturer’s name, the pile type, and the date of manufacture. Finally, the pile is ready for handling and storage, which requires careful consideration to prevent any damage or deformities. Proper storage techniques include keeping the piles in a vertical position, away from any potential sources of damage, and keeping them at a controlled temperature and humidity level.
Pile Materials
- Concrete
- Formwork
- Prestressing steel
- Reinforcement
Precast Concrete Pile Construction Procedure
In preparation for pile driving, measures to safeguard the head of the pile from shattering must be determined. These measures should be based on factors such as the end bearing requirements and driving conditions. It is also essential to ensure that the pile has reached its maximum strength before beginning construction.
Next, the precast concrete pile should be placed at the designated location. Then, the pile should be forced into the ground using an impact pile driving hammer. To protect the pile head during the driving process, a special timber packing or synthetic cushion block should be used.
Driving the pile with precision can be achieved by measuring the set. The goal is to drive the pile to a depth that equals one times the pile diameter into the resistive soil layer. By following these steps, the pile can be safely and effectively installed.
Applications
This construction material is versatile and can be utilized in various construction projects, particularly in challenging soil conditions. It is particularly well-suited for building sites with soft and thick soil, as well as those with high water tables that may pose difficulties for conventional pile construction. Additionally, this material can support large pile sizes, making it an ideal choice for constructing wind turbines, pylons, and marine structures, as well as building bridge abutments and piers that need to withstand the forces of rivers.
Fig. 4: Driving Concrete Pile
Advantages of Precast Concrete Piles
This construction method has several key benefits. Firstly, it does not produce any spoil, which is advantageous for projects where environmental impact needs to be minimized. Additionally, it is unaffected by groundwater, making it a reliable option for areas with high water tables. Furthermore, this method is cost-effective for deep foundation work, and it can be installed quickly, saving time and money. It is also suitable for a wide range of project sizes and complexities, as it is capable of accommodating both simple compressive loads and more complex combined loadings. Overall, this method is a versatile and efficient option for deep foundation construction.
Disadvantages
During the driving process of a pile, it is possible for damage to occur in a position that is not visible from the surface. Additionally, the pile may become laterally displaced if it encounters any obstructions such as rocks in the ground.
Before driving commences, the length of the pile is estimated. However, the accuracy of this assumption can only be determined on site. Short piles can be difficult to extend while long piles may prove to be expensive and wasteful.
A large rig is necessary for driving piles, and hard-standings are required to ensure that the ground surface is suitable for the pile-driving.