Bangkok’s Samsen Road Collapse: MRTA Blames Unstable Soil and Groundwater
The Mass Rapid Transit Authority (MRTA) has attributed the massive sinkhole that opened up on Samsen Road in Bangkok to unstable soil and groundwater, which caused a huge subsidence above an under-construction underground rail station. The collapse, which occurred on Wednesday morning, resulted in a 30-meter-wide, 30-meter-long, and 20-meter-deep void, with soil and water sliding into the empty platform and passenger hall of the Vajira Hospital station of the Purple Line southern extension.
Unstable Soil and Groundwater Conditions
According to MRTA governor Gardphajon Udomdhammabhakdi, who addressed a press conference on Thursday morning, the sequence of events that led to the collapse was directly linked to the condition of the local soil and groundwater. "The condition of the local soil and groundwater changed the stability and properties of the soil," he explained. "That caused subsidence which broke a water main that was installed three meters deep."
Initial Assumptions
Mr. Gardphajon began by recalling the unusual incidents before the collapse, which started around 5 am on Wednesday morning when some people spotted an uneven surface on Samsen Road. However, it was still passable at that time. Around 5:30 am, water emerged on the road surface, and traffic police arrived to block flooded lanes. The Metropolitan Waterworks Authority suspected an underground water main leakage.
Timeline of Events
The sinkhole began to subside around 6:45 am, and by 7:30 am, it had reached its full depth. A large amount of soil and water slid into the empty platform and passenger hall of the Vajira Hospital station, as well as the subway tunnel. Soil and mud flowed inside the station for a distance of about 50 meters, and for about 20 meters inside the upper tunnel.
Restoration Efforts
The MRTA governor assured that the state enterprise and its contractors are now trying to stop the subsidence and restore the usage of the area for the public as well as patients of Vajira Hospital as soon as possible. The contractor for the section in question is the CKST joint venture, made up of SET-listed Ch. Karnchang Plc and Sino-Thai Engineering and Construction Plc. The latter is controlled by the family of Prime Minister Anutin Charnvirakul.
Two-Phase Restoration Plan
The work will be carried out in two phases, with the first phase involving restoration of the immediate area of the sinkhole site. Nearly 50,000 sandbags were used to plug the hole between the subway tunnel and the station. Landfilling will then be done with cement, and then soil or sand. A temporary road surface will then be built to reopen Samsen Road, possibly within two weeks.
Phase Two: Restoration of the Purple Line Tunnel and Station
The second phase will deal with the restoration of the Purple Line tunnel and station and the repair of affected buildings, including the Samsen police station. Mr. Gardphajon assured that the MRTA had built underground railways for a decade and had always adhered to standard techniques. However, this was the "first and special incident" of its kind that had happened at an MRTA project.
Investigation and Prevention Measures
The agency and experts will thoroughly investigate the causes of the collapse to prevent a recurrence. Mr. Gardphajon apologized for the subsidence that had affected local residents and patients of Vajira Hospital, promising that the MRTA and its contractors would take care of all affected parties.
MRTA Deputy Governor’s Statement
MRTA Deputy Governor Kittikorn Tanpao stated on Thursday that inspection of other subway construction sites is underway though no subsidence nor risks have been detected yet. Sinkholes are rare in Thailand, where the geology and Bangkok’s urban landscape do not usually lead to ground collapses.
Market Reaction
Shares of Stecon fell 9% in Bangkok trading, while Ch. Karnchang slumped 7.7%, heading for its biggest loss since June.
Conclusion
The massive sinkhole on Samsen Road has caused significant disruption to traffic and daily life in the area, with many residents and patients of Vajira Hospital affected by the collapse. The MRTA’s explanation that unstable soil and groundwater conditions led to the subsidence offers some insight into the cause of this rare event in Thailand. However, the investigation is ongoing, and it remains to be seen whether any further measures will be taken to prevent similar incidents from occurring in the future.