NAT 2026 | PREVIEW


Technical areas of construction are: Overview; Mix


Design; Reinforcement; Site Considerations; Surface Preparation; Water Control; Equipment; Placement; Quality; Repair & Rehab; Safety; and, Case Studies. Proposed instructors are from the American Shotcrete


Association, Bekaert, Solomon Colors, SNF, Beton- und Monierbau USA, Mott MacDonald, Sika, Patriot Shotcrete, and Schnabel Engineering.


TECHNICAL PROGRAMME In all, the Technical Programme runs over five half-day sessions, commencing Tuesday, June 16, and finishing lunchtime on Thursday, June 18. Each of those periods has the same structure, running four themes, parallel tracks: Case Histories; Design; Planning; and, Technology. This framework holds more particular subjects of interest, in turn, as follows: Case Histories:


● Geology & Structures ● Ground Improvement & Geotechnical ● Rehabilitation & Maintenance ● Urban and Complex Challenges ● Tunnel Construction & Equipment


Design:


● Ground Behaviour & Stability ● Numerical Modelling & Simulation ● Risk & Safety ● Specialised Techniques & Innovations ● Tunnel Design & Construction Methods


Planning:


● Future Projects ● Risk ● Resiliency ● Alternative Delivery Methods ● Transportation


Technology:


● Emerging Technologies ● Equipment Automation ● Innovations in Tunnelling ● TBMs-1 ● TBMs-2


Sampling of the subjects, and wider themes, could be


done in many ways. In this case, as this issue of T&T has Rock Tunnelling among its themes, this focus will be taken to spotlight a few of the papers and presentation considering such challenges. The opportunities to learn


EVENT SPONSORS


Sponsors of the NAT 2026 gathering include: Overall: Jennmar Civil Gold: Civil & Building North America (CNBA); Herrenknecht; HNTB; Jacobs; Mott MacDonald; Skanska Silver: BabEng; Barnard; Jay Dee; Kiewit; SAK; Schnabel Engineering; Bronze: Black & Veatch; Conquip; Delve Underground; Dr Sauer & Partners; FlatironDragados; LJB Underground Services; Michels; Slipform Engineering; Subsurface & Tunnel Engineering (STE); Traylor Bros; Treviicos; Typsa; Walsh


There are to be more discussions on Rock Tunnels,


and much more, in the sessions. Go to: https://natconference.org/


about Rock Tunnelling experiences run through all days of the Technical Programme, and for example include papers on clogging, swelling, acid rocks, groundwater, and use of permanent structures early on: ● TBM clogging risk in clay-rich rock: this discusses the challenges, especially for earth pressure balance (EPB) shields when boring (cutting, scraping with liquid introduced) through the likes of claystone, siltstone, mudstone, shale, etc. The paper, from Colorado School of Mines, notes that availability of best practice guidelines is limited to help contractors define and mitigate clogging risk, and so provides some, from considering case studies.


● Modelling of swelling in time-dependent deformation: two papers look at tunnelling in through shales in the Georgian Bay Formation, where 1) shaft support and construction sequencing are considered, and, 2) risk assessment and mitigation measures on a metro project are discussed.


● Swelling tuff in wine cave needed floor fix: Improvements at a storage cave revealed problems with swelling pyritic tuff (due to oxidation, sulphate formation), leading to a new engineered floor tied down with micro-piles.


● Managing acid producing rock (APR) in tunnelling: the paper compares and contrasts the practices in the US and Canada, respectively, noting that these are needed for environmental compliance and that testing is required to assess risks and which can also help to avoid cost-overruns.


● Challenges to excavate under a rail tunnel: a rock tunnel replaced proposed micro-tunnels as the solution to route utilities below part of Amtrak’s Northeast Corridor, but varied ground near shaft locations and the high groundwater table, plus nearby tracks and only limited rock cover all added to the challenges for the alternative method.


● Permanent lining in initial works helping to reduce time and cost: initial excavation support (bolts, shotcrete, spray waterproofing membrane) has used permanent structural elements, plus pre- grouting, in soft rock recently to build metro projects in Montreal, helping to reduce time and cost. It is being termed the ‘New Montreal Tunnelling Method’.


June 2026 | 29


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