Deep Foundation Pilling
Foundations support structures by transferring their loads to soil or rock layers with adequate bearing capacity and settlement characteristics. When shallow foundations are not feasible, deep foundation piling techniques are employed, tailored to the specific nature of the structure.
Prefco specializes in various deep foundation piling methods, primarily aimed at load transfer and earth retention systems. These techniques are utilized for both marine and land-based structures, particularly in areas where surface soil layers lack the necessary load-bearing capacity. Deep foundation piling is essential for transferring lateral, vertical, or a combination of both loads through weak soil layers to a suitable bearing layer. Below are descriptions of the most common techniques used in deep foundation piling construction.
MAJOR ACTIVITIES
CAST-IN-SITU Bored Piles
Cast-in-situ bored piles are a type of deep foundation system used to support structures by transferring loads to deeper, more stable soil layers. This method involves drilling a hole into the ground to the desired depth, then reinforcing it with steel bars and filling it with concrete, which is poured directly into the borehole. The term “cast-in-situ” indicates that the concrete is poured on-site, as opposed to precast piles made elsewhere.
These piles are particularly useful in various scenarios, such as in areas with limited access for heavy machinery or when working in urban environments where vibrations and noise must be minimized. They can also be employed in challenging soil conditions, including soft or loose soils, where traditional shallow foundations may not suffice.
Cast-in-situ bored piles provide high load-bearing capacity and resistance to lateral forces, making them ideal for supporting tall buildings, bridges, and other infrastructure projects. Their adaptability to different soil types and construction requirements makes them a preferred choice for engineers seeking durable and effective foundation solutions. Additionally, they help mitigate environmental impact due to their quieter installation process compared to driven piles, aligning with sustainable construction practices.
Driven Pile
Driven piles are deep foundation elements that are mechanically driven into the ground to provide structural support. Made from materials like concrete, steel, or timber, these piles are prefabricated and installed using a pile driver, which delivers repetitive blows to embed the piles into the soil. This method is particularly effective in achieving the necessary depth to reach stable soil or rock layers.
Driven piles are widely used in various construction applications, including high-rise buildings, bridges, and marine structures. They are especially advantageous in environments where soil conditions are challenging, such as in soft or loose soils that cannot support shallow foundations. The dynamic installation process enhances soil compaction around the pile, improving load-bearing capacity.
Additionally, driven piles are effective for resisting lateral loads and providing stability against wind and seismic forces. Their use is common in projects requiring rapid installation, as they can be placed quickly and often require minimal excavation. They are also beneficial for environmental reasons, as the noise and vibrations generated during installation can be managed, making them suitable for urban settings. Overall, driven piles are a reliable solution for achieving deep foundation stability in a wide range of construction scenarios.
Continuous Flight Auger (CFA) Piles
A Continuous Flight Auger (CFA) is a cast-in-situ piling method that originated in the United Kingdom during the 1960s and has since become one of the most commonly used foundation techniques worldwide. The CFA method is particularly advantageous in environmentally sensitive areas and soft or water-bearing strata, where traditional deep casings would be necessary, thanks to its low vibration levels during installation.
CFA piles are primarily employed in projects like bridge construction and large structural foundations. They can be installed as individual piles or as part of a group, similar to driven pile foundations, providing flexibility in design and application. The process involves drilling a hollow auger into the ground while simultaneously injecting concrete, which creates a strong, stable foundation.
This technique not only minimizes disturbance to the surrounding environment but also ensures precise placement of the piles. Additionally, CFA piles are capable of supporting significant vertical and lateral loads, making them suitable for various types of structures, including commercial buildings and infrastructure projects. Their efficiency and adaptability make CFA piles a preferred choice in modern construction practices, especially in challenging soil conditions.
Pile Caps & Capping Beams
A pile cap is a robust, mat-like concrete structure that sits atop a group of piles, providing a stable foundation for the entire system. Its primary function is to distribute the load of the superstructure evenly across the piles, enhancing the overall bearing capacity and stability of the foundation. Similar in concept to a raft foundation, which also consists of a large concrete slab, the pile cap plays a crucial role in supporting heavy structures.
Capping beams, which are made from a combination of steel and concrete, further reinforce the foundation system. These structural elements serve as the base for the slab and help stabilize the surrounding ground and adjacent structures. To ensure structural integrity, steel reinforcing bars are placed on top of the piling cages according to engineering specifications.
Once the reinforcement is in place, concrete is poured over the bars to form the capping beam. After the concrete has cured, the temporary casing can be removed, allowing for excavation work to begin for the basement or lower levels of the building. This process represents a critical step in preparing the site for the capping beam pour, ensuring a solid foundation for future construction.