Nebraska DOT: 3230DT is an all-inclusive timesaver

The Nebraska Department of Transportation found exactly what it was looking for with the 3230DT – an all-in-one drill rig for field investigations.

“The 3230DT allows us to switch from mud rotary, rock coring, hollow stem or straight auger, CPT, or direct push easily and with limited time interruptions,” said Mark Lindemann Geotechnical Engineer for the Nebraska Department of Transportation. 

The NDOT’s first project with the 3230DT took place in the Nebraska Sandhills – the largest sand dune formation in the Western Hemisphere.

“We needed to get several borings and test data for a proposed sheet pile wall,” Lindemann said.  “We were able to take SPT tests through the 4.5 inch direct push casing until we got refusal in the dense sands at about 40 feet. Then, we switched over to mud rotary drilling with the casing in place.  It was nice to be able to keep going and not have to start a boring completely over.”

The NDOT splits its geotechnical drilling into three main groups: bridge foundations (deep foundations), soil mechanics (undisturbed sampling for embankments, walls, culverts, and landslides), and soil survey (bulk samples for subgrade, soil suitability, and wetland mitigation). 

“One of the things we were looking for was versatility – a one-stop shop machine that could do everything we needed to in our field investigations,” Lindemann said.  

It’s been a 10-year journey of research and approvals, but NDOT received the OK in 2016 to make the purchase. 

“We’ve been working with Lee Shaw since 2012 and he has been so helpful and patient with us,” Lindemann said.  “That is one of the factors that helped us decide which manufacturer to go with –  the prompt, knowledgeable and friendly service we have received from Geoprobe® staff.” 

NDOT took delivery of its 3230DT in 2017 but was first introduced to Geoprobe® in 2005 when purchasing a wireless Cone Penetration Test (CPT) system.  The NDOT utilizes CPT for in-situ testing and is currently performing CPT research with the 3230DT that will enable the department to design deep foundations with additional accuracy when compared to more common SPT methods. 

“The anchoring system has been a big benefit to enable us to reach the depths we need,” Lindemann said. “Another benefit is the ability to dial in the feed rate for improved CPT testing quality and less fatigue for the operator trying to hold a constant feed rate.  And finally, the head clamp makes it easier to push CPT rods to greater depths and also pull the rods out of the ground quicker and safer.”

The group is just getting started, though, when it comes to using the 3230DT to its full potential. 

“Our track-mounted 3230DT allows us to get into rugged terrain and soft ground areas we typically couldn’t access before,” Lindemann said. “We also plan on using the direct push 4.5 inch casing to install monitoring wells for wetland mitigation sites and see the direct push method as a big time-saver versus conventional drilling methods.”