Bangkok sinkhole caused by soil flowing into tunnel, which ruptured water pipes, governor says

The 50-metre deep sinkhole that opened up in Bangkok on the morning of Sep. 24 was caused by subway construction, said the authorities.

The sinkhole appeared in front of a hospital in the Dusit district.

Vajira Hospital has since closed its outpatient service and evacuated all its patients, Thai PBS World reported.

No injuries have been reported so far.

Soil flowing into Purple Line construction

Khaosod English reported that Bangkok Governor Chadchart Sittipunt revealed the cause of the road collapse.

The collapse, he said, was due to soil flowing into the Purple Line subway tunnel construction running beneath the area.

The sinkhole opened at one of the most complex points along the route — the future Vajira Hospital station.

This is where engineers are reportedly building an intricate network of tunnels and underground spaces.

Two opposing tunnels are being built at different depths, with one reaching 15 meters down and the other 30 meters down.

The station itself is 30 meters underground and is connected by a web of tunnels.

Chadchart further explained that the shallower tunnel developed cracks at a critical joint, Khaosod English reported.

He said that soil began flowing into the tunnel and the underground construction spaces.

This caused the road surface to collapse, which ruptured water pipes and caused more soil to be washed into the tunnel, which exacerbated the situation.

Future dangers

Due to dangers of the sinkhole, the Mass Rapid Transit Authority of Thailand (MRTA) released a statement, according to The Nation Thailand.

According to the statement, Thailand's Deputy Prime Minister and Minister of Transport Phiphat Ratchakitprakarn instructed his deputy and the MRTA Governor to oversee the response.

Meanwhile, the MRTA has also coordinated with the local waterworks and electricity authorities, telecommunications companies, and local police to address the situation and manage traffic.

Chadchart expressed concern about the nearby police station and shophouses "that remain in the danger zone", and said that people have to kept out of a "100-meter radius from the landslide point".

He added that "the next concern is rain", as that would lead to soil erosion and further increase the chance of landslides.

Purple Line extension project

Bangkok's MRT Purple Line connects northwest Bangkok to the central MRT Blue Line at Tao Poon station, and its extension is under construction.

The Nation Thailand reported that the construction of the MRT Purple Line (Tao Poon-Rat Burana section) is a 19 billion baht (S$764 million) joint venture between two construction firms.

Top photos via @Cam_gold_/X