Piling

 

                                           Piling                                                          

Building engineers use piling to secure the foundations of a construction site before they begin building infrastructure on top. It's a key step in the construction process that contractors use to boost the safety and reliability of a project. Piling is an important technical skill that requires confidence and a collaborative team dynamic. If you're seeking a role in the construction industry, it's essential to be knowledgeable about the different piling types and methods.

What is piling?

Piling is the process of drilling foundations through the ground to provide more structural strength to the weak soil underneath. Piling prepares the ground to carry heavy loads, such as a new home, office complex, road or another piece of infrastructure.

Piles usually are long poles that are made of timber, steel or concrete. Its shape, circumference and weight may vary depending on the conditions of the soil and the demands of the project. For example, piles may need to carry uplift loads to support taller structures, such as skyscrapers. In this case, engineers need to consider overturning forces from winds or waves. Essentially, pile foundations work by distributing the weight of heavy construction across a wider surface area.

When to use piling foundations in construction

There are several factors to consider when using a piling foundation during construction. Their primary purpose is to ensure the safety and strength of the ground before workers build anything above. Here are a few situations when using a pile foundation system can be essential:

•             When the groundwater table is high

•             When a heavy load of a superstructure needs additional support

•             Other types of foundations are costlier or not feasible

•             When the soil at shallow depth is compressible

•             When there is the possibility of scouring, because of its location near the river bed or seashore

•             When there is a canal or deep drainage systems near the structure

•             When soil excavation is not possible up to the desired depth because of poor soil condition

•             When it becomes impossible to keep the foundation trenches dry by pumping or by any other                       measure

How are piling types used in construction?

Before building engineers can decide between piling types, they need to assess the conditions of their construction site, such as the soil, climate and other relevant factors. They will also need to consult with architects to understand the scale of their infrastructure project. Using this information, they can prepare for construction challenges and decide on the most suitable piling type. At this stage, their goal is to use a piling type that boosts the longevity and structural integrity of the foundations below their build.

The following describes three common methods of using piling types in construction:

1. Driven pile foundations

Concrete, steel and timber are the most common materials used to make piles for the driven pile foundation method. Concrete piles are precast before they arrive at a construction site. Similarly, contractors order prefabricated steel and timber piles that they can drill directly into the soil with a piling hammer. In granular soils, these piles displace an equal volume of soil, helping the soil become more solid. This compaction of soil increases its density; and therefore, its bearing capacity.

However, this construction method is not suitable for saturated silty soils that have a poor drainage capacity. The watery condition deters the compaction of the soil when you drill driven piles through it. In fact, this has the opposite effect on the soil because it decreases its ability to support heavy loads.  

2. Cast-in-situ pile foundations

Cast-in-situ foundations use concrete piles. Rather than bringing in precast piles to the construction site, workers drill holes into the ground, place steel reinforcements inside and then fill the hole with concrete instead. This allows them to tailor the depth of the foundation as per the project's needs and use piles with a smaller diameter than the ones used for driven pile foundations.

3. Combined pile foundations

Combined pile foundations use a mix of the driven pile foundation process and the cast-in-situ pile foundation process. Thus, it retains the advantages of each method.

First, workers drive a steel shell with the same diameter as the pile into the ground. Next, they pour concrete into the shell to secure the foundation. This is a common method that engineers use to pile over water.

Types of piling

When determining the best piling type for a project, building engineers examine a range of factors, including:

•             The depth of the excavation

•             The angle at which the pile needs to be installed

•             The environmental issues that impact local residents

Here are the eight main piling types construction workers can consider:

End-bearing piles

The bottom of end-bearing piles rests on a layer of strong soil or rock. Engineers design this type of pile to transfer the heavy load of a building through the pile onto the strong layer. It essentially is a column that cuts through a weak layer of ground so that a structure can remain upright with the support of the strongest layer underneath.

Friction piles

Friction piles are cylindrical. They use their full height to transfer the forces a building generates into the soil. In a friction pile, the amount of load a pile can support is directly proportional to its length. This also means that at greater depths, the pile can hold more weight.

Bored piles

Bored piles need to be augured into the ground to form a hole that workers can later fill in with poured concrete. The benefit of this type of pile is that it's cast into position, meaning that bored piles are extremely secure. Construction projects in cities use bored piles because the installation process results in less vibration when compared to other methods.

Driven piles

Driven piles need a lot of force to be hammered into the ground. This type of pile is common for foundations that have non-cohesive soils or soils that contain many contaminants.

Screwed piles

Screw piles look like large steel screws that need to be fastened into the ground using a similar circular motion regular screws to attach to other surfaces, such as wood.

Timber piles

Engineers have used timber piles for thousands of years in construction. Timber piles are precast off site and installed with the driving method. They are a highly economical, safe and efficient foundation solution for temporary and permanent structures.

Steel piles

Construction workers install steel piles with impact or vibration hammers that can penetrate sturdy soil and rock. Depending on the support that your project needs, steel tube piles come in different diameter size options too.

Concrete piles

Concrete piles are common in offshore construction projects, such as bridges, oil rigs and floating airports. It's a modern tool that effectively supports vertical structural loads and lateral wave loads. It's often used to stabilize complex terrain because of how the pile reacts and the way it distributes loads through the pile.