A Beginner’s Guide to Foundation Drilling
The world of construction is full of unsung heroes, but none may be more essential and underappreciated than the realm of foundation drilling. This immensely valuable process is actually the heart of any major construction project, yet many are still a little confused as to what it actually is and why it’s so crucial.
We’re here to help fill in the blanks. Below, you’ll find all the essential information needed to understand the immense role foundation drilling plays in building everything from 50-story skyscrapers to highway bridges. You’ll learn what it’s used for, the different types of methods, and even a bit about the foundation drilling equipment and foundation drill rigs themselves.
Let’s get started by defining what foundation drilling is in the first place.
What is Foundation Drilling?
The term ‘foundation drilling’ may seem fairly self-explanatory, but the process itself can be rather extensive, covering many different methods and applications. In short, foundation drilling is a process that involves using a drill rig to bore a large hole deep into the ground in order to insert structures—such as piles—that are used to build a foundation for a construction project.
Foundation drilling can come in many forms, utilized for both new projects and existing structures. The most common use of foundation drilling is generally for new construction projects that require foundation piles, piers, or caissons to be placed deep into the ground for maximum load-bearing capability underneath the foundation’s main body.
The logic for this is simple: Larger structures need as much stability as possible. This begins by drilling deep into the earth in order to install the components that can provide that stability, leveraging the strength of immovable sediment layers such as bedrock with cement columns.
Sounds simple, right? It’s actually not. Foundation drilling is an extensive process that involves a profound level of skill expertise for the drill operator, combined with coordination from the construction site’s project manager, engineers, and more. Add to that the difficulties posed by the site’s soil composition, nearby construction, weather, and unforeseen surprises, and you can see how the “simple” process of drilling a hole can quickly become anything but.
Examples of Foundation Drilling Projects
Foundations are built under most any new construction project, whether it’s for a new home, bridge, office building, and so on. The actual foundation itself can take on many forms, with some being built just a few feet into the ground. This can be acceptable for smaller structures under a certain size or height, but taller and heavier structures typically require a foundation that can bear a much more sizable load and withstand natural shifts in the soil without sinking. Such projects call for foundations to be built deep into the ground — a situation that requires foundation drilling in order to achieve this.
One common example is any skyscraper project. Tall buildings spanning several stories simply cannot rely on a shallow foundation for a multitude of reasons. Even the slightest shift in a shallow foundation could damage the structural integrity of the entire building. This not only creates the need for costly repairs, but it may also make the entire structure dangerous to occupy. Securing a stable, secure foundation is paramount to ensure the longevity and safety of the structure. This begins with foundation drilling.
Another excellent example of a construction project requiring foundation drilling is utility poles. These poles are crucial for ensuring the delivery of power to communities all across the country; they need to be able to withstand everything from the elements to shifting soil. Powerline drilling equipment is often used to create boreholes deep enough to firmly hold the poles inside, along with drilling through stubborn rock layers that may be close to the surface.
Infrastructure needs involving foundation drilling don’t stop there — it’s also a significant part of the construction process for highways, bridges, and even piers. Foundation drilling isn’t relegated to new construction either, as it can be used to provide added stability to current structures that may be at risk of sinking or shifting. In some cases, foundation drilling techniques and equipment can be used to divert groundwater away from structures at risk of potential damage, a process known as dewatering.
Why Build a Deep Foundation?
In order to understand the need for deep foundations, it’s important to understand how a shallow foundation works.
Many houses are built on shallow foundations, which either sit on top of the earth’s surface or just below it. These foundations work well for smaller structures, but they are still subject to sinking or moving as time goes on, as they are still essentially built on top of the ground. While this is
usually a fixable problem with little danger posed to the structure itself, the same is not true for larger ones, such as tall office buildings and interstate bridges. The general concept of the foundation remains the same, but the “roots” of the foundation need to be anchored deep into the ground. That’s where foundation drilling comes in.
Foundation drilling provides an effective and standardized way to install “anchors” for the foundation that extend far into the earth to prevent it from moving or sinking. In many cases, this means drilling far enough down to where the foundation’s piles or piers rest on top of bedrock, essentially transferring the load-bearing responsibility to the most solid and immovable portion found deep under the earth’s surface. These columns are then attached to the structure’s foundation, ensuring a fully stabilized base on which to build upon.
Foundation Drilling vs. Pile Driving
When it comes to deep foundation construction, the two main options for installing piles and piers into the ground are either via driving or drilling. In this case, the term ‘driving’ refers to a hammering motion from above that drives the pile into the ground. This is done using heavy machinery and has limits to its use.
Although pile driving is an effective technique regularly used in the construction industry, it does pose some disadvantages in certain situations, such as limiting the size of the pile being used, extremely loud noise, and disturbing nearby soil and construction areas due to the shockwaves sent out from each strike from the pile driver.
Foundation drilling methods typically offer an advantage over these drawbacks. For example, with pile driving, the pile is preconstructed, which creates limits on its size and creates logistical complexities and costs that stem from transporting large piles to the construction site. With foundation drilling, the pile is created within the borehole by pouring cement inside. This allows for the creation of a perfect, form-fitting pile right there on the spot.
Constructing the pile within the ground also sidesteps the noise otherwise created by hammering a pile into the ground, along with avoiding the disturbance of nearby soil or projects that may be underway. It’s safe to say any people living or working near the construction site will certainly appreciate these aspects as well!
Common Foundation Drilling Methods
Foundation drilling can be done in several different ways. These are among the most common currently being used today.
The most common type of dry rotary drilling, kelly drilling is typically used to create large-diameter bored piles. The name refers to the “kelly bar” drill rod that can reach very deep into the ground thanks to its telescopic design. Suitable for most any soil and rock type, kelly drilling removes soil to the surface using several different options, including augers, buckets, and core barrels.
During a typical Kelly drilling process, the drill rod extends below a hollow temporary protective pile as it bores into the ground. The drill rod is then withdrawn back up to the surface, a reinforcement structure is lowered into the hole, which is then filled with concrete, followed by the removal of the temporary protective pile structure.
Continuous Flight Auger Drilling
As the name implies, continuous flight auger drilling makes use of a prominent auger drill design that continually brings displaced soil and rock to the surface throughout the duration of the drilling. With this method, the bore hole needs to be the length of the auger. Continuous flight auger drilling is a common method used for projects requiring pre-drilling and creating holes for a cast-in-place pile.
For projects with challenging soil or environmental situations, continuous flight auger drilling is often combined with double rotary drilling. This method involves placing a smooth, continuous casing around the auger, which helps control the flow and dispersion of the drill cuttings as they make their way up to the surface.
A reversed version of this method is known as full displacement drilling. With this method, drill cuttings are displaced into the ground instead of being brought to the surface and removed. This is achieved by fitting a smooth casing over the auger with a displacement attachment on the end.
Reverse Circulation Air Injection Drilling
Reverse circulation air injection drilling is used in instances where large boreholes are needed — typically up to 3.2 meters in diameter. This method involves using hydraulic circulation and a pump to flush a liquid current between the drill rod and borehole that brings drill cuttings up the drill rod and out onto the surface.
One of the oldest dry drilling methods, grab drilling is characterized by the use of a sphere-like claw with an angled end that is forcefully driven into the ground via a crane through a pre-placed casing. The drill head closes onto the soil and/or rock and is then raised to the surface so it can dispose of its contents. This process is repeated until the desired depth is achieved.
Down-the-hole drilling is usually reserved for projects with hard rocks or boulders in need of being broken up. This is achieved by mounting a hammer on the drill bit at the end of the rod. Compressed air is pumped through the bit to help break up and remove rock as the bit rotates and impacts rocks in its path while simultaneously pumping drill cuttings out of the hole and up to the surface.
Foundation Drilling Equipment
As you may imagine, foundation drilling usually involves some pretty heavy machinery. Foundation drill rigs come in many shapes and sizes, often with some unique capabilities and uses. Some rigs are more suited towards smaller projects with standard needs, while others may be equipped for larger projects in more challenging terrain, such as projects handling the building of a bridge across a lake or river.
It’s important to realize there is no one-size-fits-all foundation drill that works for all types of drilling or any variety of site conditions.
The actual type of drill rig used for a particular project depends on several factors, including:
- Depth and diameter needed for the holes
- Type of soil
- Location of project
- The layout of the construction area
Foundation drilling equipment and rigs should always be used solely for their intended purposes and nothing more. Fortunately, many drill rigs are capable of handling a few other foundation-related construction tasks as well.
There are also a number of different foundation drill tools that can be equipped to a rig to enable it to take on different types of jobs and applications. These include tooling options like adapters, augers, buckets, casing spinners, and core barrels.
In addition to tools and add-ons to drill rigs, you can also install upgrades to core components for better performance or to better match the terrain and soil at the job site. An example of this would be switching out a rig’s foundation drilling teeth with upgraded carbide auger teeth for drilling into harder soil and rock.
Today’s foundation drill rigs also offer many modern upgrades and conveniences that include features like digital dashboard screens, automatic placement, and improved torque technology.
So, there you have it. Hopefully, you now have a much firmer grasp regarding the inner workings of foundation drilling, its importance to ensuring the stability of new and existing structures, and the complexities of the process itself.
For those who are well-acquainted with the foundation drilling industry but worn out from the lack of support for drill rig operators in the field and the absence of personable, caring, and consistent customer service from suppliers and technicians, Blaze Equipment has got your back.
We founded this company in order to provide a reliable partnership that helps those in the foundation drilling industry succeed — people just like you. Our extensive background and first-hand experience in the industry enables us to offer the precise resources you need to keep your foundation drilling services running at their peak.
From service and repair to rig sales and heavy hauling, Blaze Equipment has you covered. Contact us today to find out what we can do for you!