Advances in tunneling technology discussed at Cutting Edge Conference in Dallas, TX

The SME and UCA (Underground Construction Association) “Cutting Edge” conference hosted its largest attendance yet with 285 in-person participants meeting in Dallas, TX Nov. 15–17. Attendees came from the United States, Europe, Israel and Canada and included engineers, contractors, project managers and college students. Elisa Comis from McMillen Jacobs Associates chaired the three-day event.

Priscilla Nelson, professor and head of mining engineering at the Colorado School of Mines in Golden, CO was the opening speaker and delivered a keynote address discussing crumbling infrastructure in tunnels, waterways, sewage and drainage systems in the United States and world and ideas on how to address resilience and the underground. Nelson has worked as a program director and senior advisor at the National Science Foundation, as a professor at the University of Texas at Austin, and was formerly provost at the New Jersey Institute of Technology. She is internationally known for her expertise in geological and rock engineering.

Her talk focused on the fact that cities throughout the world are growing in population and that growth is anticipated to continue in the coming years. “Our future is one of population and urban growth worldwide,” said Nelson. “It’ll be interesting to see how people want to live, considering the long-term effects of the pandemic.”

Nelson encouraged the audience to think about the often vast, public and private infrastructure systems that are frequently created independently from one another and in silos in many cities. She explained that many have been created in an uncoordinated manner and need to be considered by engineers in more of a “systems of systems” approach. The complexities and interdependence of waterways, sewage, drainage, electricity and transportation modes need to be looked at more holistically, she said.

“We have to inform the public, professionals and politicians, and provide truths, examples and answers,” said Nelson. She cited natural disasters and the recovery time it took for each including Hurricane Sandy in 2012, Hurricane Katrina in New Orleans in 2005, and the earthquake in Kobe, Japan, in 1995, lessons learned and the necessity of studying what went wrong and how to anticipate for these types of events in the future.

Crumbling infrastructure

There is growing demand for equity in any proposed Advances in tunneling technology discussed at Cutting Edge Conference in Dallas, TX infrastructure rebuild efforts of cities. Repairing and replacing water mains, gas pipelines and sewers in places like New York City, where much of the systems are 60 to 100 years old, requires consideration of what neighborhoods are most affected and where the work should be prioritized. According to Nelson, the Federal Emergency Management Agency (FEMA) does not have these potential breakdowns on its list of possible emergencies, though they should be added.

Scott Elmer from the Harris County Flood Control District presented “Going Deep to Reduce Harris County’s Future Flood Risks,” as he represented the city of Dallas’ flood control project, equating the length of it to the driving distance between New York and Los Angeles. Elmer said that historically, people did not think tunnels could be built in this area because of weak soil, yet there are lots of water and waste tunnels in downtown Dallas.

Hurricane Harvey, a devastating Category 4 hurricane that made landfall in Texas and Louisiana in August, 2017, impacted all of Harris County. Tens of thousands of homes were flooded and this generated political support for a bond package that was approved by voters. “Tunnels are one of the ways we’re looking at this differently. We were told to be innovative, and so now we are asking, ‘Can tunnels be built in Harris County?’” said Elmer, adding, “If so, can they move enough water to make a difference?”

The team has created 2D models of the entire county, establishing critical mass areas with consideration of social equity. They believe the answer is “yes” to the feasibility of the work and have moved on to phase two of the study. “We’re not quite sure where we’re going to build these tunnels—we’ll need all of you engineers and contractors in the future. We’ve got some good projects coming up,” Elmer said to the crowd.

The team considered water quality and sedimentation issues and collected data to look at the watershed and history of flooding in the area over the last 100 years. They also considered how the land was being used.

John Kinnear from Jacobs in Toronto, Canada presented on the London Thames Tideway Tunnel Project. The project involves sewage upgrades necessary because “every time it rains in London, the system goes over and into the river,” said Kinnear. He explained that in London, the river generally drains to the east, and that the Thames water management project is run by a private utility, which is a common practice in England, and in this case, amounts to managing systems worth £4.2 billion pounds (equivalent to $6 billion U.S.).

Jacobs has developed a reference design for the project and the work is being done as design/build contracts. The Thames is made up of clay to the west and above the river is mixed sand and gravel.

Milton Brooks with the City of Dallas and Paul Smith, Black & Veatch, discussed “Changing TBM Excavation Diameter Mid-Tunnel in Dallas.” When Dallas was founded in the 1920s it was a much smaller city, and as it began to develop, it spread east and north. Brooks shared that deep, underground tunnels have never been built in this city, but the need has become apparent as there is “$4 billion worth of property to protect in Dallas.”

The city is trying to build an alternative outfall for the current drainage system to reduce possible flooding, moving from a 9.1 to 10.7 m (30 to 35 ft) section. The soil in the build area is made up of soft limestone, is 8 km (5 miles) long, and currently has seven shafts. Completely paid for by the city of Dallas (no federal or state funds), the project is estimated to cost $210 to $285 million.

On Wednesday of the conference attendees who had preregistered visited the Mill Creek drainage relief tunnel project site and learned about its design change from a horseshoe to round tunnel design.

Brad Grothen from Robbins presented “The Future is Noncircular: TBM Solutions for Flat Inverts,” and discussed recent advancements in nonround tunnel designs. These include noncircular tunneling and mechanized excavation for soft ground and soft rock. He shared lessons learned from the company’s work at the Fresnio Mines in Mexico, where the geology is hard rock.

“Grouting and Greasing in Frozen Ground” was presented by Sean Grant of Traylor Bros. He is a registered civil engineer working in Los Angeles and shared about the company’s recent work experience on a tunnel in Vancouver, Canada. The project was challenging and involved highly variable geology with abrasive ground and rock.

Werner Burger from Herrenknecht discussed TBM technologies of the future. Burger, a mechanical engineer, said the company is focused on optimizing existing technologies, including those in operator assist systems for slurry and hard rock machines.

Also in attendance and presenting were Mark Stephani of HNTB on the topic of resilience through design, Angel Del Amo of Aldea Services on building tunnels that cross fault lines in Los Angeles, and Mark Funkhauser of McMillen Jacobs Associates on geotechnical considerations and the alignment selection for the lower Olentangy Tunnel in Columbus, OH.

Mike Rispin of Strata Worldwide led a panel discussion on research and development “from idea to implementation.” There was discussion of the typical length of time it takes to complete projects; whether owner, contractor and designer all need to be in alignment for innovation to take place (the consensus was not necessarily); and how to work cheaper and faster. Alternative design and build delivery methods, how to measure innovation and its effects, the increasing cost of projects, inflation, supply chain and labor shortages were all reviewed.

Around the discussion of innovation, Bill Edgerton, SME president, said “we innovate to do things we haven’t done before.”

During the UCA Young Members session, Sean McDonald from Jay Dee discussed next generation technology and climate change. Katherine Westerlund from Mott MacDonald led a carbon portal and building information and modeling (BIM) integration talk, and Rachelle McDowell from Atkinson discussed working through the pandemic on the courthouse commons tunnel in downtown San Diego, California.

Federico Bonaiuti from Lane Construction in Italy presented “3D modeling for Tunnels: A Tool for Inspecting and Foreseeing Construction Activities from Planning to Execution.” McDonald discussed the “Down for That” website and young member development initiatives.

In the afternoon, Sanja Zlatanic and Brandi Crawford of HNTB gave an update on the DART D2 subway project in Dallas using 3D animation to show the progress. The project has brought 150,000 jobs to the area.

Nick Chen from Jacobs discussed the Amtrak East River tunnel reconstruction project. During Superstorm Sandy, four of these train tunnels were flooded. Chen said the reconstruction project involves a “total organ transplant, to use an analogy of the body,” because the tunnel is over 100 years old. One of the tunnels in the project is underwater, and issues like egress from the train to inside parts of the tunnel in case of fire or emergency must be considered. Fire, life safety, ventilation, drainage and building redundancy into the construction methodology are all aspects to be addressed. Chen said that the project schedule is a fast, 16 months and there’s been “lots of knowledge gained and lessons learned.”