States Boost Their A-GaME

Advanced geotechnical methods in exploration (A-GaME) is a set of technologies promoted by Every Day Counts (EDC) to increase the accuracy of subsurface investigations for improved project design and construction. States are making the most of their site characterization programs by using A-GaME techniques such as measurement while drilling (MWD), cone penetration testing (CPT), and seismic and electrical geophysics.

New Hampshire and Florida Advance MWD

As part of a project to widen and improve a major corridor, the New Hampshire Department of Transportation (NHDOT) instrumented a rig to use MWD to better understand the engineering properties of the soil and rock.

MWD can be used in any type of soil or rock, records continuously, and does not require additional effort from the driller. A relative advantage of MWD is that it can distinguish boundaries and material changes with greater precision and accuracy than intermittent sampling methods, as measurements are taken continuously.

NHDOT used MWD on this project to enhance geotechnical site characterization and provide continuous monitoring and recording of data during the drilling process. This technique allowed NHDOT to add information between standard penetration tests and get real-time information in between the traditional 5-foot samples. This helped with site characterization and enabled the driller to know, in real time, how the drill was responding to the subsurface materials.

The Florida Department of Transportation (FDOT) used MWD at a site near Dowling Park as part of ongoing research investigating the benefits of MWD for drilled shaft quality assurance and quality control (QA/QC) applications.

The Ocala Limestone formation at the site has historically been challenging for site investigation as the bedrock is soft-porous, often highly weathered, and possesses a high degree of strength variability and spatial uncertainty. FDOT conducted MWD on test shafts to assess the measured drilling resistance compared to the load-tested shaft side shear capacity. The relationship between drilling resistance and shaft side shear capacity was then used to estimate performance on untested production shafts.

Because MWD was conducted in the footprint of the future production shafts, spatial uncertainty was eliminated, and the strength variability and side shear capacity of each shaft were directly assessed. This application of MWD helped confirm the engineering design was appropriate at each production shaft location. FDOT is continuing its development of MWD as a QA/QC tool for drilled shafts and developing a new protocol for MWD that will improve and speed-up decision-making when encountering problematic shafts.

Michigan and New Mexico Learn from User Groups

The A-GaME team continues to reach, assist, and grow a community of practice through three user groups. Each of the three groups represents an area promoted by A-GaME—CPT, MWD, and geophysics. Groups have member support from, but are not formally affiliated with, American Society of Civil Engineers Geo-Institute committees, Deep Foundation Institute committees, Transportation Research Board geotechnical committees, and FHWA.

These technical transfer and discussion forums enable efficient cross-organizational communication and exchange of thoughts and ideas. Members discuss best practices, lessons learned, and application of technologies in novel situations; answer questions; and collaborate. “The user groups are guided directly by user interests and needs,” said Benjamin Rivers, FHWA A-GaME team lead.

The Michigan DOT (MDOT), which has more recently adopted CPT, participates in the CPT user group.

“The presentation and discussion topics in the group have covered the full range of CPT from planning and performing CPT, collecting good data, interpreting CPT data, and designing with CPT data while using real project experiences,” said Erron Peuse of MDOT. “As a newer CPT user, being involved with the CPT user group has been a way to connect with more experienced users, which has been very helpful for us as we get started using and continue to further develop our CPT program. We have implemented several best practices learned from the group and the topics covered in the group give us confidence in the results that we are getting.”

The ability to learn both benefits and challenges of using a particular technology can be valuable to States as they grow their areas of practice around specific geophysical exploration techniques.

“Attending the MWD user group allows me to hear about the successes as well as challenges that others have run into while trying to implement MWD,” said Melissa Bates of the New Mexico DOT. “Prior to attending the webinars, I realized that these methods had some advantages; however, applying the methods in a practical way could be difficult. Without these presentations, it was sometimes difficult to find practical technical resources meant for geotechnical engineers that were up-to-date and had the appropriate level of technical background. The user group makes using these methods feel less intimidating.”

EDC Outtakes: A-GaME

Derrick Dasenbrock, FHWA geotechnical engineer and A-GaME team member, said they encourage participation from those willing to share their A-GaME experiences and those looking to learn more. “These user groups are for anyone interested in, or curious about, advanced geotechnical exploration methods,” he said. “Individuals are welcome to join and help continue to build these robust, interactive communities of practice.”