Method for Constructing Piles

Driven and bored/ cast-in-situ piles are two primary methods for building foundations and piling on construction sites. Although you may find more types, such as driven and cast-in-situ piles, aggregate piles, etc., all the others are variations of Driven and bored/ cast-in-situ piles. Here is a comprehensive overview of these piling construction methods.

Driven Piles Foundations

Driven piles are a type of pile foundation that are constructed by driving a precast or prefabricated pile into the ground using a pile driving hammer or similar equipment. This method is also sometimes referred to as driven pile foundations.

The process of constructing driven piles involves the following:

1. Preparing the ground by excavating any soil or debris and compacting the soil to provide a stable foundation.
2. A pile-driving hammer is then used to drive the precast or prefabricated piles into the ground to the required depth.
3. A pile cap, used to distribute the structure’s load evenly across the pile, is installed on top of the pile.
4. The foundation of the structure is constructed on top of the pile cap.

Note: The piles are usually made of concrete, steel, or wood and can vary in shape and size depending on the design requirements of the structure.

Driven piles can support heavy loads in various soil conditions, including loose or soft soils. Driven piles can also be cost-effective for large projects, as they can be manufactured off-site. However, their installation can generate significant noise and vibration.

Bored/ Cast-In-Situ Piles

Bored or cast-in-situ piles are a type of pile foundation constructed by drilling a hole into the ground and filling it with concrete or other materials to form a pile; the piles are created on the site, unlike the bored, where the precast piles are installed. This method is also sometimes referred to as drilled piles or auger-cast piles.

The process of constructing bored piles involves the following:

1. Drilling a hole into the ground using a drilling rig equipped with a drill bit. The design requirements of the structure determine the diameter and depth of the hole.
2. A steel reinforcement cage is then lowered into the hole, and concrete is poured into the hole using a concrete pump or similar equipment.
3. Once the concrete has set, the top of the pile is trimmed to the required level, and any protrusions or deformities are removed.

Bored piles can support heavy loads in various soil conditions, including hard or rocky soils. They are commonly used in urban areas where noise and vibration from driven piles may be disruptive and can be a good option for sites with limited access or space.

However, they can be slower and more expensive to construct than driven piles due to the specialised equipment and materials required to complete the construction process.

For your information, there are subtypes of the bored/ cast-in-situ piles used for different purposes. Here is an overview of these types.

Rotary Bored Piling

Rotary bored piling is a type of bored pile construction method in which a drilling rig equipped with a drilling tool is used to excavate the soil and create a hole for the pile.

A temporary casing is installed into the hollow structure to support when pouring the concrete and other material. The concrete is poured, and the steel frame is installed; the casing is removed immediately after installation when the concrete is not set yet.

Continuous Flight Auger (CFA) Piling

In the CFA piling method of bored piles, a hollow-stemmed auger is used to drill into the soil while concrete is continuously pumped through the hollow stem of the auger.

The auger is withdrawn from the hole while concrete is pumped through the hollow stem, creating a continuous concrete column. Unlike the rotary bore piling, there is no need to install the temporary casing.