Find out how pile driving can be an efficient method of installing deep foundations and discover solutions to the challenges of pile driving
Published 2 Jan 2023
Pile driving installs long, slender support structures into the ground. The process involves using a large machine to drive the piles into the earth until they reach the required depth.
Pile driving is often used to construct foundation supports for buildings and other structures. It’s also possible to use the process to install fencing, erosion control barriers, and signposts. It’s an efficient and quick way to install deep foundations and causes minimal disruption to the surrounding area when performed with pile drivers.
Here are several advantages of pile foundations:
While they have many advantages, there are also several disadvantages to pile foundations, including:
A pile driving system is composed of four main components: lead, hammer cushion, helmet, and pile cushion. Together, they work to transfer energy to the piles, which impacts how well the hammer performs.
The pile driver lead is a support beam that guides the piling and hammer. Depending on how they are suspended from the pile driver, they are either hanging, fixed, or swinging. Leads keep the pounding and hammer in sync.
A shock-absorbing hammer cushion, usually constructed from man-made materials, is positioned between the striker plate and helmet.
Helmets are steel caps placed atop piles. It protects the head during driving.
A pile cushion is usually made from wood and serves as a buffer between the helmet and the pile.
Pile drivers come in several types, such as:
Vibratory hammers slice through the soil to create piles rather than pound them using a spinning and counter-weight system. Hydraulic motors provide the power for this operation while a crane or excavator lifts the hammer. The pile is attached to the vibratory hammer via hydraulic clamps. Creating piles is faster and emits less noise (comparatively).
A two-stroke diesel engine powers this drop hammer. The operator raises the ram, then drops it onto the pile. As the ram hits the pile, its momentum drives it back up. The machine will continue until the fuel runs out or it’s manually stopped.
With a shorter stroke, these hammers increase the blow rate when the ram is accelerated during the downstroke, and pile-driving speed increases.
A hydraulic hammer employs an outside power source to raise the hammer to the top of its arc. For a single-acting hydraulic hammer, the energy that drives the piston down comes from gravity, like a drop hammer or a single-acting air/steam Hammer.
The inherent challenge of pile driving is that it deals with soil and that there are a lot of potential problems with this setup. But if you plan and consider all the likely issues that come with pile driving, you can be better prepared to mitigate them. Include solutions in your contingency planning, so you don’t exceed the budget, among other issues. Here are some common challenges and solutions:
Before starting, calculate how many times the pile driver needs to hit the ground to make the pile as deep as required. It depends on the soil and the driving system. If it takes more hits than we thought it would, there is a problem with the soil or the driving system.
Always match the driving system to the pile type before starting any work. If already matched, verify that the driving system operates according to the equipment manufacturer’s guidelines. Inadequate driving system performance can be due to insufficient hammering efficiency or too-soft cushioning. The soil may have more strength, a higher damping ratio, or larger soil quakes than initially tested for.
Borings must be taken if the blow count of a group of pilings changes. The pile toe is likely damaged if there is no indication of a weathered profile above the bedrock. If the pile is too damaged to inspect from the inside, use dynamic measurements to evaluate the problem. If that is not possible, you will have to extract the pile.
There are two possible explanations for a lower-than-anticipated blow count: either the soil’s resistance is low, or the performance of the hammer is better than average. If soil resistance is lower than anticipated, you will need restrike testing. It entails calculating the setup factor and driving at a reduced capacity. Evaluate hammer performance and make adjustments as required.
If the blow count is lower than expected, check the soil borings. The pile may be broken beneath the grade if there’s no sign of soft layers. In addition to evaluating the tensile stresses along the pile, you should also check for compressive stresses at the toe. Some other possible causes of this issue include a spliced pile, an obstruction, or uneven contact at the toe. Inspect the toe area for any damage that may have occurred.
A restrike test is needed to discover any soil strength changes. If deeper piles are driven into the soil than initially estimated, it may be because of lower soil resistance than anticipated. Or, it could be due to increased driving system performance. A structural engineer will then determine if changes need to be made in the driving system or pile depth.
If the piles unexpectedly move, it’s a sign that an issue needs to be fixed before work can resume.
The piles have likely failed due to soil displacement if they move laterally when new piles are being driven. However, the failure may be coming from an adjacent slope. To solve this issue, you can change the sequence of pile driving or re-drive the installed piles. You may also be able to reduce ground movement by predrilling pile locations.
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Pile joints allow precast concrete piles to be driven to lengths greater than 30m or almost 100ft. Usually, concrete precast piles can only push down to around 30m, but in specific circumstances—such as offshore projects—they can sometimes extend up to 150m.
While there is no set depth for all foundations, the best foundation depths vary depending on many conditions, such as:
If you’re looking to build on shallow foundations, less than 2.5m is an excellent depth. If the area you’re building is close to another structure, take precautions so that your excavation work doesn’t damage or undermine it. In some cases, you may need to extend your foundation as deep as the adjacent building’s foundation.
It depends on several factors, including the type, height, and presence of nearby obstructions and how close you can pile near a building. Generally, you should leave a minimum of 750mm from the face of an obstruction to the centerline of a pile, which means that internal basement walls should be at least 1200mm or more from the nearest pile. Additionally, it is recommended that you consult with a professional engineer or contractor to determine the best approach for piling in your particular situation, as factors such as soil conditions and other construction work may impact your ability to pile safely near a building.
There are two main types of piles: end bearing and friction. End-bearing piles transmit loads directly to a strong layer of soil or rock below the surface, while friction piles rely on friction between the surrounding soil and the pile to support a load.
Pile driving can be challenging, but with iAuditor, you can streamline your operations and ensure everything runs smoothly. SafetyCulture is a multi-purpose inspection platform, and it's perfect for helping you manage your pile-driving process. With iAuditor, you can do the following:
Rob Paredes is a content contributor for SafetyCulture. He is a content writer who also does copy for websites, sales pages, and landing pages. Rob worked as a financial advisor, a freelance copywriter, and a Network Engineer for more than a decade before joining SafetyCulture. He got interested in writing because of the influence of his friends; aside from writing, he has an interest in personal finance, dogs, and collecting Allen Iverson cards.
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