Efficient Seismic CPT Includes Live Views of Data

Passionate about delivering exceptional geotechnical, environmental, and instrumentation exploration services, the TERRACON CONSULTANTS INC office in Savannah, Georgia, went from being without in-house drilling resources in 2021 to running three Geoprobe^® rigs, operating full time. The rigs are a 7720DT, a 6622CPT, and a new 7822DT.

"We now support Terracon drilling offices across Georgia and into Florida and South Carolina," Logan Richard, drilling manager, said. "The diversity of our fleet allows us to accomplish a variety of drilling objectives — from environmental Macro Core^® soil sampling, well installation, cone penetration testing (CPT), dilatometer (DMT), and Standard Penetration Testing (SPT) with our 7822DT and 7720DT, to dedicated and highly efficient CPT operations with our 6622CPT."

Depending upon the job specifications, any of the three rigs can be found running the Geoprobe^® seismic cone penetration testing (sCPT) module.

"Its modular nature makes setup from rig-to-rig quick enough to perform sCPT whenever it is deemed necessary," Richard said.

Many people don't realize the Southeast is a seismically active area.

"In 1886 Charleston experienced a massive earthquake estimated to be a magnitude of 6.9-7.3,” John Mnieckowski, geologist, said. “Because of this historic event, we now know that Savannah is within a seismic zone as dictated by the International Building Code. Naturally, seismic analysis is a crucial element of our geotechnical drilling.”

Conducting liquefaction analysis increases the importance of obtaining quality data with an efficient system.

"Our rigs are oftentimes miles deep into undeveloped forests, which means having a reliable system is highly important," Richard said. "We rarely go to a jobsite just to perform an sCPT, meaning we need cross-compatibility between CPT and sCPT."

Both Mnieckowski and Richard feel they found the solution when they added the Geoprobe^® sCPT module to their resources a little more than a year ago.

"Several parts offered by Geoprobe^® have made cross-compatibility possible for us - notably the blade mounted rod and tooling rack, which allows us to have a set of wired rods for sCPT and a set of non-wired rods for wireless CPT both ready to use at a moment’s notice," Richard said. “Compared to our previous system, it is much more advanced.”

Three factors influence their preference for Geoprobe^® seismic CPT module, including:

• VIEWING DATA IN FIELD – “You can see the shear wave velocity in a zoomed, real-time view in the field. Velocity waveforms appear on the screen as the program processes them during data collection operations. Previously it was difficult to tell if you’d collected poor quality data. Now you can readily make adjustments in the field by simply clearing the strike and trying again after adjustments.”
• STACKING WAVES – “You can easily stack the waveforms to determine more accurate average velocity at different depths.”
• EFFECTIVE COMMUNICATION — "With the real-time view Geoprobe^® software offers, drillers are able to efficiently communicate their findings with engineers via text or phone call."

Ensuring quality data from the field contributes to overall team efficiency.

“It takes effort to prep and mobilize to a site, and then to be blind to what data you’re collecting is frustrating and inefficient. We now can see quality of the data in higher detail in the field and if there are problems, allow our operators to make adjustments in the field versus learning days later the data was insufficient or lacking is a tremendous advantage,” Mnieckowski said. “Additionally, setup of the new system is quick and modular. Plug in four wires, snap magnetic strike boxes to each side of your rig, and you're ready to go.”