When you think about foundations, what comes to mind is the concrete slab that is poured on top of the ground to offer a foundation for your home. Foundation drilling is different; this is when big machines or pieces of equipment are used to drill holes into the ground called shafts. This is mainly done to create a strong foundation for big structures like bridges and tall buildings. Such structures require deep foundations, which are achieved through foundation drilling.
The General Idea
A machine is used to drill a deep hole in the ground, and then concrete is poured into the hole. This process forms what you hear being referred to as bored piles, drilled piers, drilled shafts or caissons. These drilled shafts run deep in the ground to help keep a large structure stable, even in the case of flooding or earthquakes.
Before drilling starts, specialists have to consider various factors:
The Type of Structure To Be Built
This helps determine how deep or wide the hole needs to be. The larger or the more likely a structure is to be unstable, the wider and deeper the hole needs to be.
Soil and Rock Composition
This mainly helps in two main things: first, the soil and rock properties are tested to find out whether they are suitable in offering sufficient stability for the structure. If not, measures are taken to guarantee structural stability. Secondly, the properties of the soil and rocks help in choosing a suitable drill/machine/rig/piece of equipment for efficient and effective drilling.
When choosing a suitable drill, the terrain, accessibility, location and tightness of the construction site needs to be considered as well. This ensures that the drill fits into the construction site and moves about easily. When needed, a silent drill can be selected for noise or vibration reduction.
Drills You Might Come Across
Some of the common drills you might come across include the following:
Kelly Drill: This is the most common drill because it is suitable for different soil and rock properties. It is also suitable where larger diameters are required.
Continuous Flight Auger Drill: This is mostly used for predrilling and installing cast-in-place piles for particular soil properties. As drilling takes place, soil and rock is loosened and conveyed continuously by a continuous flight auger.
Double Rotary Drill: This drill is similar to the continuous flight auger drill, but it has an additional feature: a continuous casing. The auger is inside a casing.
Down-The-Hole Drill: This is mostly used when the soil and rock are very hard. It uses a hammer and compressed air to help with drilling.