Piling 101: Piled foundations and their use within construction
What is piling?
Piling can generally be defined as the process of strengthening or supporting a structure. Speaking more technically, piling is often thought of as foundations that are driven or bored into the ground at specific points in order to transfer loads within the soil. Often, piling is associated with structural unbalance or ground weakness. The process of inserting piles into the ground provides stability and reliable support to the targeted building as well as the immediate environment surrounding the structure. Piles go through various layers of soil until a solid layer of rock, or soil, is reached. The supports are then added, serving as a foundation for the building which will distribute the weight of the structure through the ground evenly. Generally piling is used when a combination of factors are present. Existing foundations or trenches may be unstable or too costly to remove, a high-water table may be present which could impact soil stability, furthermore the site chosen may have ground which is unsuitable and unable to support the load of the planned structure without additional support. Piling can be used in a variety of scenarios, from supporting large buildings and structures, such as skyscrapers and bridges, to smaller projects like home extensions and outbuildings.
Essentially, piled foundations are used when the load bearing capacity of the soil is considered to be inadequate for the proposed structure. Piles transfer the load, and associated pressures, to solid ground situated beneath the poor ground conditions.
A brief history
Piling is a traditional construction method which has been used globally for thousands of years. Historically, many villages and towns were situated close to rivers and lakes due to the close proximity to water. Despite the convenient location, the ground conditions surrounding these aquatic environments were often unsuitable for building on due to the weak bearing soil. Therefore, in order to ensure structural stability, the ground was enforced with timber piles which were either forced into the ground or fixed into holes and filled with stones and sand. Numerous examples of early piling has been documented around the globe, including numerous bridges and churches.
Traditionally, timber was the most popular material of choice to use for piles due to its lightweight mass yet robust and durable nature. Timber was, and still is, notorious for being easy to handle and prepare, making it an ideal material to use for construction purposes. For many years timber was the most commonly used material within the piling industry, up until fairly recently when alternative materials like steel and concrete were introduced. As a consequence of the construction industry modernising, as well as the evolution of building materials and manufacturing processes, over time timber has been largely replaced by steel or concrete piles. These newer materials are able to be fabricated into a larger variety of shapes and lengths, as well as being able to sustain compressive bending and tensile forces beyond the capacity of timber. At present concrete and steel are the most popular material choices due to their robustness, multifunctionality and flexibility within projects. Steel is regularly cited as being extremely durable due to its ability to withstand hard driving, as well as being easy to work with and fabricate.
In addition to deciding upon materials, it’s important to think about pile design. Piled foundations should be sympathetically designed to take into consideration soil conditions and the load bearing pressures expected. Piles should be designed to withstand axial, shear, and bending stresses which can develop naturally when horizontal movement occurs between the piles and various soil layers. Depending on the environment, piles may be required to carry uplift loads when used for taller structures or those subjected to high wave or wind forces, or lateral loads in marine surroundings from the impact of berthing ships. Furthermore, combinations of vertical and horizontal loads are expected in contexts such as bridges, piers, and retaining walls. It is important to consider both the pile material type and installation method, along with the ground conditions and loading pressures. If one or the other is unsuitable for the intended environment, an entire project or structure may fail.
At Piling Equipment Ltd, we have a range of piling rigs and foundation drilling machinery capable of completing a variety of piling techniques. Our two most popular piling methods are continuous flight auger and driven piling; however we have an assortment of rigs suitable for working within a variety of modes. To learn more about our machinery and equipment, browse our website or take a look at our catalogue today.
CFA Piling: Continuous flight auger piling is one of the most requested and widely used methods across a variety of projects and locations. This piling technique requires drilling a continuous flight auger into the ground, the auger holds the soil surrounding the hole which eliminates the need for temporary casings and support fluids. Once the required depth has been met, concrete mix is pumped through the hollow stem whilst it is being retracted from the ground. There are many benefits of using this method including minimal vibration and noise production, enabling the piling to be undertaken in close proximity to other structures and buildings. CFA piling is a fast and economical method which is suitable for a wide range of projects and ground conditions, including challenging topography types. The CFA method can also be used for the installation of continuous wall piles.
We have a wide range of CFA compatible piling rigs, including our Geax machines. We are also able to provide mini piling rigs capable of conducting SFA (sectional flight auger) piling. This is a similar method to CFA, except the auger is made up of shorter hollow stem sections. SFA piling is best suited to environments with low headroom or restricted access.
Driven piling: Driven piles are suitable for most ground types and conditions. Piles are driven into the ground using a hydraulic hammer causing the ground to compact and densify the surrounding soil. Like the CFA method, there are lots of advantages to using driven piles within a project. Piles are able to be precast to meet the required specification, meaning various lengths, sizes, and shapes can be manufactured in advance and then transported to site. Alternatively, tubular steel piles are able to be used where more difficult ground conditions are likely to be encountered, such as sand or gravel bands, or deposits containing boulders. Driven piling is a robust solution which is both time and cost effective. Additionally, driven piling does not generate soil arisings meaning a site which requires less preparation.
When it comes to drop hammer machines, we have a few different options. Our most popular drop hammer rigs are the Cobra D-series machines, a compact yet powerful mini rig capable of working on restricted sites with limited headroom and tricky ground conditions.
To learn more about our current hire fleet and sales inventory, browse our website or take a look at our current catalogue. Our team are always happy to answer any questions, or to provide additional information about any of our rigs.