Phiphat orders 15-day probe into Doi Luang tunnel collapse
A 15-day probe has been ordered into the Doi Luang railway tunnel wall collapse, with officials reviewing safety standards and construction causes
- Transport Minister Phiphat Ratchakitprakarn has ordered a fact-finding committee to investigate the collapse of the Doi Luang tunnel wall, with findings required within 15 days.
- The investigation will determine whether the collapse was caused by an unavoidable event (force majeure) or by defects in the construction process.
- An initial assessment suggests the collapse of a five-square-meter section was due to continuous rainfall saturating waterproofing material that was being installed.
- Officials state the incident will not affect the railway project's expected 2028 opening, as the tunnel requires further layers of concrete reinforcement.
Transport Minister Phiphat Ratchakitprakarn has ordered a fact-finding committee to investigate the collapse of part of the Doi Luang tunnel wall on the Den Chai-Chiang Rai-Chiang Khong railway project, with the findings required within 15 days.
Phiphat said the incident occurred during construction of Contract 3 of the new railway line, covering the Chiang Rai-Chiang Khong section.
He said he had instructed all relevant parties to tighten construction supervision and strictly follow ISO standards after the accident. The newly appointed committee will examine whether the collapse was caused by force majeure or by defects in the construction process.
“At present, no contract has been cancelled and no contractor has been blacklisted,” Phiphat said. “However, I confirm that there will be no exemption or special treatment for any contractor. If wrongdoing is found, action will be taken equally against all parties under the regulations.”
Deputy Transport Minister Siripong Angkasakulkiat said initial information indicated that the collapse followed continuous rainfall in the area.
He said the section of the tunnel wall affected was being prepared for waterproofing installation. The waterproofing material absorbed a large amount of rainwater, causing an area of about five square metres to collapse.
Siripong said the Department of Rail Transport had already begun an inspection and expected the true cause to be known within 15 days.
The ministry has instructed construction teams to further tighten safety and worksite standards. Siripong said the incident would not affect future rail services through the tunnel because the construction process still requires another two to three layers of concrete reinforcement to strengthen the tunnel wall.
He added that investigators had not ruled out any possible cause and would examine all aspects carefully. The ministry would take legal or disciplinary action where required, without granting any exception to any contractor.
The Den Chai-Chiang Rai-Chiang Khong double-track railway project had recorded cumulative construction progress of 64.448% as of May 2026, compared with a planned target of 65.092%. This means the overall project was behind schedule by only 0.644 percentage points.
The project is still expected to open for service in 2028.
Contract 3, covering the Chiang Rai-Chiang Khong section, has made faster progress than planned. Construction progress stood at 59.722%, compared with a target of 56.794%, placing it 2.928 percentage points ahead of schedule.
The Doi Luang tunnel in Chiang Rai is part of Contract 3. The contractor is the CKST-DC3 Joint Venture, comprising CH. Karnchang Public Company Limited, Sino-Thai Engineering and Construction Public Company Limited and Chiang Mai Construction Company Limited.
The contract is worth 19.385 billion baht.
