Deeper, Faster, Better CPT Data and Operations

When F&ME CONSULTANTS INC needed to balance demanding government transportation and infrastructure assessments with commercial and private foundation projects, geologist Craig Piercy knew their cone penetration testing (CPT) capabilities needed an upgrade.

"We were looking for something that we could mobilize in emergency situations, move around job sites faster, and complete soundings faster than borings with a traditional drill rig while collecting continuous data," Piercy said.

Speed wasn't the only concern. CPT data quality had become a persistent challenge.

"We've used other CPT systems that don't give you confidence in seismic velocity readings," he said.

Choosing a New Path

After evaluating their options, FME in South Carolina decided to partner with Geoprobe^® for an entirely new CPT configuration: a 20CPT press on tractor and ASTRA15 cone with true interval seismic.

“Geoprobe^® has a longer track record with drilling equipment, so we had confidence in their 20CPT press rig,” Piercy said. “We also thought the Geoprobe^® DI CPT Suite software was more impressive.”

Piercy traveled to Geoprobe^® headquarters in Kansas for hands-on training with CPT specialist Cory Harvey, running the press and software through its paces.

“Cory gave me great advice and helpful recommendations during the training,” Piercy said. “It was good to check out the manufacturing side of Geoprobe^® also. The machining of the tooling is done in-house.”

Field-Proven CPT Data Results

After completing three deep holes with the new setup, Piercy knew they’d made the right decision: "We like it more than what we were doing before."

• 20CPT Press on Tractor: “Heavy-duty components are used to build the press, which is very easy to operate. We can take the tractor almost anywhere. The constant 2cm/sec head feed rate is convenient and gets our CPTs deeper than pushing from the back of a conventional drill rig.”
• ASTRA15 Cone: “Works better than the 10cm2 cone because it keeps the sleeve friction off the rods so you’re able to push deeper. It’s also more robust than a 10cm2 cone. The Geoprobe^® cone is very well-built and the components are well made.”
• True Interval Seismic CPT: “The true interval eliminates trigger errors when doing seismic testing. The instant feedback of velocities in the field gives assurance that the velocities being collected are reasonable. Visually, it’s great looking at the data and having confidence in the seismic shear waves being collected by two geophones for every hammer strike. The seismic data processing software gives you many options to chose from to help you determine the best velocity analytic model to use.”
• Geoprobe^® DI CPT Suite: “It's very user-friendly and integrates quality control checks that are not a feature on other CPT platforms I’ve used in the past. It’s easier to run and teach other people how to use it than what we were using before. Geoprobe^® DI CPT Suite software is just easier. The integrated zero values at the beginning and end of a push help verify CPT data quality and ensure ASTM standards are being followed.”

Proving Ground: A Critical Foundation Project

FME recently deployed the system on a critical infrastructure foundation project at the Columbia Canal. A sinkhole had formed next to a drilled shaft, prompting excavation and soil recompaction. They needed assurance that no additional voids remained.

"We did eight CPTs all around the foundation in question and found a small void that could have easily been missed using conventional drill rig sampling methods," he said.

A Partnership Built on Support

FME values the relationship they've built with Geoprobe^®.

"Geoprobe^® customer support is top notch, with most parts made in house. If we have an issue, it can be fixed," Piercy said. "We can send the cone off to Kansas or get the press serviced in Hickory, North Carolina."

And when questions arise?

"We can send Geoprobe^® CPT experts an email or a call and they're more than helpful — even if it's just something I forgot from training," he said.

The Bottom Line

For FME, the investment has delivered on every front:

• Confidence from better CPT data
• Capability to push CPT deeper
• CPT data accuracy by eliminating trigger errors with single-strike dual shear wave recording

"Overall, any equipment that increases the quality of CPT data collected in the field is what I am looking for," Piercy said. "And I have been very happy with the added value that we have seen from our new ASTRA15 CPT cone, true interval seismic, and 20CPT press from Geoprobe^®."