Pile Construction and Installation Overview

Piling rigs, typically track-mounted, are specialised plant items designed for installing specific types of piles. Driven piles employ hammering, jacking, or vibrating methods, using percussion hammers, hydraulic drivers, or rams. Diesel-powered vibratory drivers are also utilised to reduce ground resistance, facilitating the pile’s insertion into the ground.

Bored piles, on the other hand, utilise a continuous auger resembling a large drill bit with diameters ranging from 300mm to 900mm. Larger-diameter piles may use circular bits up to 1200mm in diameter. Piling Essex rigs for this purpose is substantial, with weights reaching 180 tonnes.

Piling in Bridge Construction:

Piles play a crucial role in providing robust foundational support for bridge abutments to withstand the structural load. When constructing bridges on land, the piling process aligns with traditional methods. However, for bridges over bodies of water, the installation of piles involves the construction of a watertight enclosure known as a cofferdam. After enclosing the area, water is pumped out to facilitate pile construction.

Safe Working Platforms:

Piling rigs come in various sizes based on the required pile type and depth. These rigs must manoeuvre and position accurately for each pile location on an area referred to as the piling platform. Piling platforms are typically created by compacting a coarse, granular fill layer to a specified depth. This fill may be brought to the site or generated from on-site demolition rubble, particularly in brownfield developments.

The piling platform distributes the load from the tracks, preventing bearing failure and minimising settlement for the rig’s safe operation. Proper design by a qualified engineer, considering soil data and piling rig loading specific to the site, is essential for working platforms. The contractor is responsible for construction, regular inspection, and maintenance of these platforms.

The Federation of Piling Specialists (FPS) highlights that many Dangerous Occurrences reported by their members are related to piling platforms. They emphasise that every Dangerous Occurrence or ‘near miss’ involving the platform has the potential for fatality. The principal contractor on-site is responsible for designing and constructing the piling platform, often contracting the design to a professional engineer.

Distinguishing Between Bored Piles and Driven Piles:

As previously mentioned, driven piles represent a conventional piling method where the pile is forcefully inserted into the soil, enhancing its load-bearing capacity. On the other hand, bored piles involve the creation of holes in the ground through drilling, subsequently filled with concrete.

The primary disparity between these two pile types lies in their construction process. Driven piles are prefabricated off-site and later positioned on-site, offering a swift construction process. However, their drawback is the generation of substantial vibrations, making them unsuitable for compact sites. In contrast, bored piles are crafted with concrete directly on-site. They are preferred for their non-disruptive impact on soil, elevated load-bearing capacities, and resilience against seasonal disturbances like frost penetration.

Construction Methods for Bored Piles:

Execution of bored piles demands specialised machinery and proficient operators. The initial phase involves the deployment of the drill rig and initiating the drilling process for the hole. Typically, the hole is drilled in sequential sections, with each section excavated and lined with casing before advancing to the subsequent section.

Upon achieving the required depth, the reinforcement cage is carefully lowered into the hole and accurately positioned. Subsequently, concrete is pumped into the hole from the base, employing a tremie pipe to ensure precise concrete placement and eliminate any voids or air pockets. The concrete is generally added in stages, allowing each segment to set before incorporating the next.

Once the concrete is in place, the summit of the pile is commonly sealed with a steel or concrete pile cap. This cap evenly distributes the loads from the superstructure above onto the pile. Reinforcement bars embedded in the concrete usually connect the pile cap to the pile, enhancing structural integrity.

CFA piling contractors play a vital role in the construction industry, especially installing foundation piles using the CFA piling method. Their responsibility encompasses various crucial aspects throughout the construction process.

Firstly, CFA piling contractors are tasked with conducting thorough site assessments and soil investigations to determine the optimal foundation solution for the specific project. This involves analysing soil conditions, load-bearing capacities, and potential piling process challenges.

Once the groundwork is established, CFA piling contractors are responsible for selecting and mobilising the appropriate equipment, including CFA rigs, drills, and support machinery. Efficient coordination of these resources ensures a seamless and timely piling operation.

CFA contractors meticulously execute the drilling and concreting process during the piling phase, adhering to engineering specifications and industry standards. They monitor the quality of the piles, addressing any issues promptly to maintain the foundation’s structural integrity.