Road Collapse on Charoen Sanitwong Traced to Old Canal, Heavy Rain, and Trucks
A road collapse on Charoen Sanitwong Street near Fai Chae intersection was caused by an eroded underground canal, heavy rain, and truck traffic; authorities rapidly deployed repair crews to restore the major Thonburi route.
Authorities have identified the cause of the road collapse near the Fai Chae intersection on Charoen Sanitwong Street as an old canal beneath the surface, combined with heavy rain and truck traffic. Multiple agencies rushed to inspect and repair the area after the incident disrupted traffic on this critical Thonburi route. At 4 p.m. on May 9th, Deputy Bangkok Governor Vishnu Saemphon visited the site and announced that repair crews and engineers were mobilized to fix the collapsed section, with completion targeted for that evening to restore normal traffic flow.
Since the road serves as a major route connecting multiple areas including Buddhhamonthon Lane, Tha Phra intersection, and Wang Lang-Siriraj, delays in repairs risked severe traffic congestion. Traffic police coordinated partial road closures and temporary tunnel diversions until the area could be cleared and repairs completed.
Daw Sithigulmanit, project supervisor for the water tunnel, revealed that the area was originally an old canal with an existing bridge. Although elevated railway construction had been completed in the area, the underlying soil along the old canal remained intact clay. This clay gradually eroded, creating cavities along the canal route. Currently, a siphon pipe is being installed beneath the tunnel, requiring excavation to 12-15 meters depth using 2.5-meter diameter piping, with directional boring coming from the opposite side.
When asked whether the soil had entirely disappeared from the old canal area, Daw explained that the original canal fill may not have been sufficiently compacted. The underlying clay soil experienced movement over time, creating cavities along the canal line. While the opposite side had been completed, this side's boring had just reached this point. Cavities had been detected and preparations were underway to drill and inject concrete to fill the voids, but heavy rain combined with heavy truck traffic caused the road to collapse before this work could be completed.
Daw noted that around 1 p.m., unusual road surface conditions appeared after the first vehicle passed. By 2 p.m., when a second heavy trailer truck passed, the road suddenly gave way. The team aimed to clear the area and complete preliminary repairs by night to restore normal traffic flow. Currently, coordination is underway to plan repairs for full restoration of the road.
