30 MARCH 2023 Geotechnical, Foundations, and Pilings by Ronald B. Peterson Drilling Products Specialist, Mountainland Supply Company In the construction market, some of the applications are geotechnical, foundations, and pilings. Each of these operations usually involves drilling or excavating in some manner. Geotechnical drilling covers a broad spectrum of drilling or sampling methods which help construction teams better understand the geology or makeup of the soil they are going to build on. It involves investigating the subsurface formations to collect data. Information gathered through geotechnical exploration will be used to determine the correct method of completing the project. It might indicate how deep to place pilings and footings into the earth so they remain stable, or it could help discover unique soil conditions which need to be accounted for in the construction planning and completion. Geotechnical drilling companies can deploy several different versions of this investigative technique to help clients gather the information they need. Here is an overview of the most commonly used types of geotechnical drilling: Direct Push Technology (DPT) - DPT is a sampling technique which involves pressing specially designed drill rods into the ground using weight or percussion. It’s one of the most cost-effective versions of geotechnical drilling and is perfect for most shallow applications. However, it is often limited by depth refusal. If you have to dig very deep into the earth or through tough material like rocks, then another type of geotechnical drilling may better fit your goals. Hollow Stem Auger - Hollow stem auger is a technique that leverages torque and force to send a screw-like assembly through tough formations. It is a relatively inexpensive technique that works well in sand, clay, and silty formations. You probably won’t want to use a hollow stem auger if your site is full of rocky or dense materials because depth refusal is likelier to occur when using this strategy in those types of environments. Sonic - Sonic drilling cuts into the earth by resonating a series of connected steel drill pipes. This technique creates a basically undisturbed continuous core sample of site materials with limited refusal. This makes it a good fit for teams that need to look very closely at a site’s underlying geology. Sonic is a more advanced drilling style, so it requires specific equipment and teams with proper training, which means you will pay more if your site needs this technique. Rotary - Rotary is a term often used to describe several closely related types of geotechnical drilling. The common thread is each technique involves cutting into the ground with a rotating bit suspended by a drill pipe. The main benefit of this technique is it can be used to achieve greater depths of penetration and larger borehole diameters. There are several different types of rotary drilling, which makes it a more versatile method. Rotary drilling uses a drilling fluid which can be formulated to provide the properties needed to successfully control the formations and complete the hole. This makes it easier to use rotary drilling on projects with more difficult geology. Wireline and Diamond Coring - These two methods involve using a rotating core barrel and a diamond bit to cut through tough formations and provide a minimally disturbed sample. If you’re looking for a fast, efficient way to collect samples from your site, this could be your best option. Pilings and foundations typically require a geotechnical evaluation prior finalizing the design and method of completion. Thanks for reading. As I often say, “A man has to know his limitations.” Working together, it is amazing where we can go. Let’s enjoy the trip! If you have any questions about this topic or if you have another topic you would like addressed, please remember this column is ours. Help me make it of value to you. It needs to be an interactive tool. I need your feedback. Send your suggestions to Michele (below) and she will get them to me. Ron Ron Peterson may be contacted via e-mail to michele@ worldwidedrillingresource.com C&G WorldWide Drilling Resource® May Issue Deadlines Space Reservation: March 25th Display & Classified Ad Copy: April 1st
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