On Monday, September 14, 2026, the 2nd Technical Seminar on Road Tunnel was held at the Platinum Hall of Avani Ratchada Bangkok Hotel in Bangkok, Thailand. The seminar provided an opportunity for Thai and Japanese stakeholders to share expertise on construction technology, quality control, and safety management for mountain tunnels.

Eisuke Otsu of Eight-Japan Engineering Consultants Inc. (EJEC) participated as a member of the JICA Expert Team and delivered a presentation entitled, “Design for Constructability: Technical Problem-Solving and Construction Management”.

The seminar addressed technical issues across the full life cycle of mountain tunnels, from planning and design through construction and maintenance, and shared practical knowledge for ensuring quality and safety. Presentations covered Thailand’s experience in mountain tunneling and geotechnical risk management, together with approaches developed through Japanese investigation, design, and construction practice.

In the afternoon session, Professor Nobuharu Isago of Tokyo Metropolitan University, Mr. Otsu of EJEC, and Mr. Masashi Nakaya of Hazama Ando Corporation each delivered a presentation on advances in tunnel technology, design for constructability, and advanced construction technologies and safety measures.

The seminar was organized in morning and afternoon sessions featuring Thai and Japanese specialists. Mr. Otsu spoke in the fifth session, explaining how design for constructability can anticipate and manage construction-stage issues from the design stage.

Mr. Otsu defined constructability in mountain tunneling as more than simply making construction easier. He described it as a design capability that anticipates uncertainty in ground conditions and enables appropriate management and response during construction. His presentation emphasized the importance of connecting site investigation, design, construction planning, field implementation, and feedback as one continuous process.

The presentation explained how design documents can be developed not as static deliverables, but as practical action rules for decision-making during construction. By clearly documenting key design assumptions—such as anticipated ground classes, allowable displacement, and water inflow—and by defining responses for predetermined threshold levels, project teams can improve construction safety, quality, and schedule stability.

Japanese case studies were also introduced, including early identification of landslide risks and optimization of tunnel alignment and structural design to protect groundwater. These examples demonstrated how risk reduction during design can avoid extensive redesign and additional countermeasures during construction.

The seminar brought together stakeholders involved in tunnel engineering to exchange knowledge on construction technology, quality control, and safety management for mountain tunnels. A presentation of tokens of appreciation and commemorative photographs followed the presentations.