The Driller by Tony Kraut
Hi. I’m Tony Kraut with Watson Drill Rigs. I’m the Sales Manager here at Watson. And we’re a four-generation family-owned business. We build foundation construction drilling equipment that serves multiple industries. We put them on excavator mount, truck mount, and crawler mount, and even crane mount drill attachments.
Watson Drill Rigs right here from Fort Worth, Texas. We’re made in America with Texas pride and workmanship in every product that we make. Everybody on our team believes in that product and believes in the contractor who uses that product who’s out there to use it as a tool to serve his needs.
A driller is a term that’s given to a skilled professional that has a responsibility to penetrate the earth with a rotary and a feed device in search of whatever resource that he’s been tasked with. A lot of drillers– and when you hear the term driller you think of oil or water or gas. And those are common driller terms also.
But there’s also other types of drilling applications that are used. They include blast hole, exploratory drilling, and construction drilling, which is what we’re going to talk about today. In construction drilling application, the driller is given the responsibility to drill a bored shaft down to a predetermined formation. And a rebar cage is then placed and concrete is poured to support the structure.
Within these few minutes, I’d like to talk to you about those roles and responsibility the driller has, as well as some of the challenges he’s going to face and some of the responsibilities he has to ensure the quality product at the conclusion of the project.
There are several common terms used for drilled shaft construction. They include drilled shaft, drilled caisson, drilled pier, bored pile, or cast-in hole drilled pile, which is commonly used on the West Coast. All of those reference a drilled shaft construction project, which is an excavated bore hole that’s down to a predetermined elevation of competent material.
Once that’s sourced and identified, then the rebar cage is then installed inside the bored pile and concrete’s poured to the surface to support the load as designed. So the structural engineer meets with the architect to determine what the column loading requirement is of that structure.
Whether it’s a single level, double level, or a bridge construction, it has a weight. It has some mass to it. So the structural engineer needs to determine what that weight is and convert that to column loading, as to what diameter and to what depth those drilled shafts need to be to be able to support that structure. Column loading is calculated in kips in the industry.
So once this drilled shaft design is implemented, then it’s given to the general contractor who will hire a specially subcontracted driller to go out and execute the project as designed. It’s very important that we reference as designed, so the driller understands what his requirements are.
Now, the driller has a choice. He has a choice on what rig to take to that job site. He has a choice in what tooling to take to that job site. But what he doesn’t have a choice in, is what diameter drill and to what depth to drill, because he has to follow the instructions of the design as it was predetermined. So it’s very important that we consider that.
And it’s amazing some of the different geology we have on our Earth and some of the different things that have created the topographic that we have, that we see today. And it’s an evolution of 4 and 1/2 billion years to create what we see here.
But there’s layers of history that lie below the surface where we are now that expose the tectonic plate movement, volcanic activity, sedimentary and erosion, all the stuff that’s unknown to the normal person. But a driller now has an opportunity to penetrate those soils and expose that evolution of changing Earth as we have it today.
And he sees that and he brings material to the surface that’s never been to the surface in a million years. And I think it’s kind of exciting to be a driller and you see that soil, you see that changing rock, and you wonder, how did this get here? What made this happen? And it’s is a study of history and a lot of people specialize in studying that. But the fortunate thing is, the drillers, you get to expose that.
But more than that, is as you’re penetrating that soils you’re going to get a different response to that drill rig. That drill rig is going to have a different erratic rotation or smooth rotation as you change in those transitional zones. And it’s exposing that hard sedimentary rock to a soft clay layer or a saturated sand layer or even the basement rock of granite. Once you penetrate into that, you’re going to get different erratic responses in those transitional zones.
And why is that important? Well, the drill responds differently. And the driller being a professional, he needs to be monitoring that drill rig as to how that tool’s responding down that hole. Because his end objective, as we mentioned earlier, is a straight drilled shaft is his end product.
It’s got to be on center. It’s got to be on location. It’s got to be in the right trajectory. And those changing soil conditions, if a driller is very aggressive, he could get that hole to deviate off. And trying to straight a crooked hole is harder than if you drilled it straight the first time.
I have the fortunate opportunity to work here at Watson and see the maturity of the different transitions from the different generations. And I met Jack Watson when I first started here in 2004. And Jack always said that a drill rig does two things. Turns and pushes.
Now it’s up to the driller to decide how fast or how slow or how hard or how light to push. Because you’re going to get a different performance of that drill tool in this changing soil conditions. But the driller could tune the tool to those soil conditions because its ultimate objective is to maintain a straight hole. And by adjusting the speed and the rotation, he can get that tool to advance properly.
And obviously, it’s an economic issue. We have to maintain an optimum penetration rate to get that drill shaft done in an expected amount of time period. So there’s a balance of that. But ultimately, it’s better to take your time and drill a hole straight the first time.
As the driller excavates that shaft, that’s the first step of a three-stage process that he has to do to execute the product. Because really, the driller advances a hole, but really he’s a manufacturer. By a manufacturer, he’s producing this drilled shaft product. And the drilled shaft product is not complete until the steel rebar cage is set in place and concrete is then poured to the surface. And it’s very important that steel rebar cage is centralized in the drilled shaft.
If you’ve ever poured wax into a mold or used a casting and poured concrete into a casting, like a statuary or a plant or whatever it might be, and you pull the mold away, the solidified product inside is your end product that you’re trying to create.
Realize the drilled shaft is very much the same thing. That drilled shaft is the mold in which that drilled shaft is going to be poured into and that’s the shape that it’s going to be forevermore. You can’t change it after that concrete is in there. That’s your end product. So it’s very important that that drilled shaft is straight and on target, and on point, to the right depth. Because that’s going to be the end product as it is.
To centralize the rebar cage, we recommend Quick-Lock® Pier Wheels and Quick-Lock Pier Boots® on the bottom of the vertical rebars to help centralize that rebar cage in the drilled shaft. Because it’s very important that concrete is allowed to flow externally off that rebar cage and make skin friction contact with the drilled shaft itself. And that that rebar cage is then encased in that concrete to prevent erosion and degradation of the shaft, which ultimately leads to the failure of that drilled shaft.
The concrete is also as important that it’s introduced properly so that there’s not an anomaly and it flows evenly outside that rebar cage from the bottom to the top. Now, many people may pour the concrete through the top or they may introduce it through a trimming pipe from bottom to top, displacing any fluid off the top of it so they ensure 100% flowability of that concrete throughout the shaft.
We’re fortunate that there’s professionals out there that design the foundation for our structures. Most people that use the building, the library, the office building, the bridge, the power line that delivers power to the home, have no idea the foundation that all of those things sit upon.
Because wherever they are, the foundation may not be stable. So it’s important that we have stability of that foundation, and that’s where drilled shafts are so important is they transfer that load down to a competent static layer that will support that structure regardless of what happens on the surface.
Now, I applaud those people that are in this industry and out there every day in the mud turning the auger, making holes. The designers that design these foundation elements for the benefit of us. Future generations will be rewarded because of the work that’s done today. And populations will continue to grow, infrastructure will continue to have to be developed, so there’s always going to be opportunities in this construction market.
And I recommend and applaud anybody who’s considering coming to the construction market. There’s great opportunity. There’s great reward. There’s also great challenges, which keeps it quite interesting. So I thank you very much for your time and look forward to visiting with you someday in the future. Thank you.
This video was made courtesy of Pieresearch, “The Standard of Excellence”! Manufacturer of high-quality alignment and centralizer products for the deep foundation and earth retention industries.