Bangkok: The Engineering Association has revealed three academic scenarios as possible causes for the recent collapse of Samsen Road. The Structural Engineers Association of Thailand has analyzed the situation, suggesting that the foundation of the Samsen Police Station may still be repaired without a complete demolition. Historical data indicates that issues with tunnel construction in soft soil have previously occurred in Bangkok and surrounding areas.
According to Thai News Agency, Prof. Dr. Amorn Pimanmas, President of the Structural Engineers Association of Thailand, held a press conference addressing the sinkholes in Bangkok’s soft soil, which followed the road collapse on Samsen Road in front of Vajira Hospital. After visiting the site with the association’s executive committee, Prof. Dr. Amorn identified soft soil, groundwater, and underground construction as key factors. The construction of a subway station at Vajira Hospital, involving two stacked subway tunnels supported by soil, played a significant role.
The cause of the collapse remains under investigation by relevant agencies. The Structural Engineers Association has proposed three collapse scenarios: Model 1 suggests that the supporting soil between the tunnels flowed into the lower tunnel, destabilizing the upper tunnel. Type 2 posits that the soil lost its bearing capacity, leading to the upper tunnel’s collapse. Type 3 considers structural damage to the tunnel itself, which could initiate a collapse.
The scenarios remain academic assumptions, but the impacts necessitate immediate actions: filling the sinkhole to prevent further landslides, reinforcing damaged structures like the Samsen Police Station, and assessing the damaged tunnel for necessary repairs.
Past occurrences of road collapses due to underground tunnel construction include incidents at Wat Bo Temple in Pak Kret District, the Nong Bon Water Drainage Tunnel, and Udomsuk Road near the Khlong Kled Bridge, highlighting the recurring nature of such problems.
Mr. Chulert Jitjuajun, Vice President of the association, expressed confidence that the Samsen Police Station can be repaired. The building’s multiple foundations and structure have suffered damage primarily to one foundation, but not severely enough to warrant demolition. Repair steps include concrete filling, backfilling with soil and EPS foam, and foundation reinforcement, using available technology to avoid total demolition.
He also referenced a 2022 incident on Udomsuk Road caused by a leak during the construction of the Nong Bon Lake underground drainage tunnel. This resulted in significant road and building damage, with repairs completed after more than three years.
Mr. Wattanapong Hirunmalai, Secretary-General of the association, discussed a 2019 ground collapse in Samut Prakan Province due to a large underground electrical conduit tunnel construction, causing extensive damage to nearby structures.
The Structural Engineers Association of Thailand has proposed measures to address these issues, including independent investigations, re-examination of similar projects, raising safety standards, and implementing real-time soil movement monitoring systems to provide advance warnings.