Microphone image, GAP 2019

How do overloaded trucks impact the near- and long-term performance of roadways? How should we manage runways in karst environments? What is the impact of ballast fouling on railway safety and maintenance? These are just a few of the high-level questions asked—and for which solutions were advanced—during the inaugural GAP conference.

Geostructural Aspects of Pavements, Railways, and Airfields was held 4 – 7 November 2019 in Colorado Springs, Colorado. Minerva TRI, which developed GAP 2019 in conjunction with representatives of multiple federal transportation agencies, treated the 120 delegates to a more intimate conversation and networking-focused event than is typical these days.

By design, the event was different.

Sessions were limited to four speakers for every 90 minutes to give ample time for presentation and debate. Breaks between sessions were set at 30 minutes minimum. All gathering tables were set between rows in the small exhibit hall. Full hot breakfasts, more elaborate appetizers, lunch buffets, and open bars each evening were provided.

GAP 2019 logo

The result was an event that kept the geotechnical conversations buzzing throughout the days. In an infrastructure environment in which the geotech’s concerns and decision making are pushed aside in favor of cost control discussion and a seemingly simple, clean surface on a project (regardless of what is going on beneath), the GAP conversation was exactly what the field needed.

RELATED: The Benefits of Accelerated Pavement Testing on Infrastructure


One of the core pieces of GAP was the guidance of federal agency personnel in developing the event. Mike Adams (Federal Highway Administration), Ted Sussmann (Federal Railroad Administration), and Jeb Tingle (US Army Engineer Research and Development Center) served as co-chairs for the conference. They were joined by colleagues including Jennifer Nicks (FHWA), Hugh Thompson (FRA), Amanda Kessler (Amtrak) and others. Together, they helped secure Transportation Research Board non-financial sponsorship for the conference and brought key people into the event’s program, including ERDC Director and USACE Chief Scientist Dr. David Pittman and Vulcan Materials’ Kevin Vaughan. The latter brought the crucial aggregates perspective on behalf of the National Stone, Sand, and Gravel Association (NSSGA).

Additionally, major transportation research centers contributed substantially to the technical program. These included (but were not limited to):

  • The University of Illinois – Urbana-Champaign (Prof. Erol Tutumluer)
  • The University of Texas – Austin (Prof. Jorge Zornberg)
  • The University of Nevada – Reno (Prof. Elie Hajj)
  • The University of Texas – El Paso (Profs. Soheil Nazarian, Reza Ashtiani, Cesar Tirado, Danniel Rodriguez)
Jorge Zornberg, Erol Tutumluer
Profs. Jorge Zornberg and Erol Tutumluer led a new full-day short course on Geosynthetics for the Design of Pavements, Railways, and Airfields. Dr. Tutumluer also delivered conference closing remarks on geotechnics and transportation infrastructure.

Class I railroads (e.g., BNSF), major engineering and construction firms (Schnabel, Bechtel, Kimley-Horn, etc.), and military entities (US Army ERDC, US Air Force Academy) sent participants and presenters.

For short courses, Prof. Jorge Zornberg and Prof. Erol Tutumluer presented a new course: “Geosynthetics for the Design of Pavements, Railways, and Airfields.” The course was very well received and will certainly be presented again.

Prof. Soheil Nazarian, Dr. George Chang, and Prof. Mehran Mazari presented a half-day course on intelligent compaction, which was a lesser known topic among the attendees but one which built a true interest as word was extended through the event. (Ingios Geotechnics’ presence in the technical program and exhibit hall helped raise the profile of intelligent compaction and its many benefits.)

Furthermore, the Transportation Technology Center, Inc., which is operated by the American Association of Railroads (AAR), hosted a technical tour at its vast site (48 miles of track!) outside Pueblo. There, they showcased cutting-edge research in track design, monitoring, and safety. The Federal Railroad Administration and private research car operator ENSCO were on hand to showcase the technology on FRA’s DOTX 218 and DOTX 220 monitoring cars.


The plenary sessions at GAP were structured to provide provocative ideas, calls to action, and greater interaction with the audience.

Transportation consultant Mark Marienfeld (President, TreadMark) provided the November 4 welcome address ahead of the opening reception. His topic, “Geosynthetics Protect Our Transportation Assets,” highlighted not just benefits of geosynthetics in particular applications but a little “finger wagging” as to why the adoption rate of geosynthetics in transportation was still fairly low, a point of both concern and consternation considering the well quantified cost and performance advantages.

ERDC team at GAP 2019
Dr. David Pittman (center) delivered the GAP 2019 keynote. He was joined at the event by many of his US Army Engineer Research and Development Center colleagues.

The following morning, Michael Adams (FHWA), Kevin Vaughan (Vulcan Materials), Ted Sussmann (FRA), Jeb Tingle (ERDC), and Eli Cuelho (TRI Environmental) set the stage for the day’s technical sessions with an engaging roundtable that was geared more to challenges and contributions from the audience. The panel discussion speakers, seated in comfortable chairs in a “talk show” setting, took turns making very short presentations that introduced questions for the field. Are we training engineers correctly? Do we need to tie transportation engineering more to operations and safety? Are we undercutting our sustainability goals with how we specify aggregates? It was a lively conversation that ended much too soon.

On November 6, the conference was treated to a fascinating address from Dr. David Pittman, the Director of ERDC and the US Army Corps of Engineers Chief Scientist. Dr. Pittman’s keynote focused on “Cutting through the Complexity: How USACE Is Revolutionizing.” It was a timely address and spot on for GAP. Dr. Pittman discussed the historical connection between military geotechnical engineering and civil infrastructure. He addressed challenges in funding and the difficulty in more quickly bringing geotechnical innovations into practice—topics everyone in the room related to. And, he emphasized the Three Cs, which could have served as the overall conference theme: Collaborate, Cooperate, Communicate.

To close the event on November 6, Prof. Erol Tutumluer (UIUC) issued remarks on the activities of ISO Committee 221 and the growing important of transportation geotechnics. His remarks served as a final call to action, with an invitation for attendees to continue the conversation at the 4th International Conference on Transportation Geotechnics (4ICTG) in Chicago, 30 August – 2 September 2020.


As noted, the 12 technical sessions were limited to four speakers in each 90-minute block. While many conferences push 6 or 7 speakers into those time frames, GAP was designed to allow full presentations to be made so that conversation could follow. Many of the high-caliber presenters took the opportunity to focus on the presentation and interaction over submitting a paper. In fact, 27 of the 48 presentations were designed only for live presentation. This allowed more timely information to be included and more pressing questions to be asked.

The main session topics were:

  • Aggregates & Ballast
  • Asset Management
  • Condition Assessment (2)
  • Design & Construction (2)
  • Designing with Unbound Layers (2)
  • Geosynthetics (2)
  • Infrastructure Degradation: Evaluating & Forecasting
  • Subgrade & Ballast Characterization

Attendees were treated to dialogue on the effect of fines on aggregate bases, lightweight expeditionary airfield systems, base design for concrete pavements, ballast fouling, geotechnical asset management for transportation agencies, inverted pavements, the US Army rail inspection program, and much more.

It was an energetic series, one supported greatly by the longer breaks between sessions so attendees could linger on topics, sit together, and meet with vendors.


Exhibit hall vendors play an important financial role in all events. For GAP, the organizers ensured that its vendors were recognized not only for their commercial role in the field but for their importance in the overall dialogue and their many technical contributions.

All exhibitors were given multiple full registrations (versus “Exhibit Hall Only” badges), so that their voices were welcomed in every plenary and every session.

Many of the exhibitors sent technical experts to present: CQA Solutions, Geo Products, Geopier, HUESKER, Ingios Geotechnics, Presto Geosystems, Sol Solution, TenCate, Tensar, TRI Environmental, and URETEK.

Additionally, Earth Science Systems, Olson Engineering, and Sol Solution contributed personnel and technology for demonstration at TTCI during the November 7 technical tour.

Other exhibitors included FODS Trackout Control Mats, Geosynthetica, Hanes Geo Components, Makes Media, Nicholson Construction Company, and Propex (which brought welcome address speaker Mark Marienfeld).

TTCI tour group image
The technical tour at TTCI was well attended. It offered participants demonstrations of railway monitoring equipment, time to explore the DOTX 218 and 220 railway research cars, and opportunity to discuss TTCI’s Class I Railroad Operator and Federal Railroad Administration research.


GAP proved how much geotechs want to be more forward in the conversation and why they need to be heard, especially in transportation engineering. The recommendations they make in design, construction, and monitoring have enormously beneficial information and results for infrastructure.  They show how an asset management perspective can save many millions for states and municipalities. They show how the utilization of advanced condition assessment technologies increases safety and provides real long-term data on why the geotechnical components of a transportation system are performing well and lowering costs. They make an incredibly compelling case for recognizing unbound aggregate as the most important asset in our roadways and how much infrastructure suffers when we do not protect that base.

GAP focused on what lies beneath, both in terms of subgrade and the subtext of our transportation engineering discussions. It focused on gaps in communication. It took a hard look at the past, and through the assessment of data, sharing of design approaches, and demonstration of technology it forecast a bright future—so long as we listen.

The organizers thank our speakers, presenters, sponsors, and participants. GAP 2019 was a truly unique gathering. We are excited to learn with you again.