Police station and residential buildings evacuated after giant sinkhole opens in Bangkok, Thailand.

Several residential buildings as well as the Samsen Metropolitan Police Station remain closed after a sinkhole approximately 30 m wide and more than 15 m deep opened up beneath the Samsen Road in the Dusit District of Bangkok, Thailand, on Wednesday 24 September 2024. The nearby  Vachira Hospital has been able to remain open, benefiting from a system of deep piles intended to keep it stable during Earthquakes. The sinkhole swallowed a number of vehicles, as well as several electricity pylons, but nobody was injured during the incident.

A massive sinkhole which opened up in Bangkok, Thailand, on 24 September 2025. Chalinee Thirasupa/Reuters.

Sinkholes are generally caused by water eroding soft limestone or unconsolidated deposits from beneath, causing a hole that works its way upwards and eventually opening spectacularly at the surface. Where there are unconsolidated deposits at the surface they can infill from the sides, apparently swallowing objects at the surface, including people, without trace. 

Bangkok is known to be prone to such problems, being situated on a flat plain of alluvial sediments, and having historically suffered from widespread subsidence due to over-extraction of water from underlying aquifers. This incident was initially linked to heavy rainfall in the area, linked to the local rainy season, which peaks in September. However, subsequent investigations have suggested that vibrations from tunnel excavations for a new subway system may have led to the breakage of a water main, causing water to gush into, and erode, the soft sediments beneath the Samsen Road.

Water gushing from a broken water main into a newly opened sinkhole on 24 September 2025. Thailand Construction News.

Soil liquefied by the initial water main break flowed into the under-creation Purple Line Tunnel, creating a void which undermined further water mains, causing them to sag and break, releasing more water and causing the rate of erosion to increase, leading to the dramatic emergence of the sinkhole at about 7.00 am on 24 September. 

This situation was made worse by initial attempts to fix the problem, which involved pouring 700 cubic meters (about 1500 tonnes) of liquid concrete into the hole. This concrete also found the gap into the tunnel system, with its additional mass causing a 30 m² breach into the tunnel system to open up, through which the concrete flowed into the tunnel.

Engineers must now wait for the concrete to set before clearing out and stabilising the breach, then filling in whole, whilst at the same time preventing water from the seasonal rains entering the hole. Initial concerns that the newly constructed Samsen Metropolitan Police Station would need to be demolished have now been dispelled, but engineers are warning that it may be over a year before it is possible for it to reopen. 

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