Bangkok Sinkhole Forces Halt on $2.2B Subway Extension

A dramatic sinkhole swallowed a part of a central Bangkok roadway on Sept. 24, forcing Thailand’s Mass Fast Transit Authority (MRTA) to halt building on the town’s $2.2-billion Purple Line metro extension and order emergency stabilization.

In a Sept. 25 technical replace, MRTA acknowledged that soil and water infiltrated by means of a spot on the station–tunnel interface of Vajira Hospital Station, undermining the stacked 6.30-meter-diameter twin tunnels. 

The collapse was compounded by the rupture of a 1.2-m water major, which accelerated soil loss and triggered the pavement failure. The authority acknowledged that “subsidence was noticed earlier than full pavement failure occurred” and pledged to revive visitors earlier than transferring into longer-term structural repairs.

Authorities stated no deaths or accidents occurred, with the early-morning timing limiting visitors on Samsen Highway. The water-main break brought on localized flooding and repair interruptions; a close-by police station was evacuated and sealed off till inspections are full.

Native media reported that Gov. Chadchart Sittipunt described the breach as about 30 m² in dimension and stated crews are focusing on an Oct. 8 reopening of Samsen Highway, utilizing stabilization layers of sprayed concrete, sand-cement fill and crushed stone.

Police have launched an investigation into the incident, in response to the Bangkok Submit, with native shops reporting that the governor declared the world a catastrophe zone to speed up the response.

Bangkok sits atop thick layers of soppy Holocene clay overlying older Pleistocene and Pliocene sediments, a geologic profile that contributes to widespread land subsidence and complicates underground building.

Vajira Hospital, immediately fronting the location, had suspended outpatient providers for 2 days however “inpatient providers continued with out ibrnterruption,” it stated in an announcement following the highway failure. Normal operations resumed Sept. 26.

Purple Line Extension

Work on the southern extension of Bangkok’s Purple Line—divided into six civil-works contracts—started in March 2022. AECOM named because the challenge designer, says the 14.3-mile plan is predicted to be accomplished in 2027.

Bangkok sits atop thick layers of soppy Holocene clay overlying older Pleistocene and Pliocene sediments, a geologic profile that contributes to widespread land subsidence and complicates underground building. Picture courtesy of ResearchGate

The road’s planning was formed by early assist from the Asian Growth Financial institution, which offered technical help starting in 2017 to conduct due diligence on engineering, procurement, environmental and resettlement points.

Whereas Thailand in the end declined ADB financing, the financial institution’s work produced suggestions on multimodal integration and fare harmonization that fed into authorities transport coverage. CKST-PL Joint Enterprise is liable for the Vajira Hospital section, with PMCSC-1 as proprietor’s engineer.

In line with Nation Thailand, an English-language day by day in Bangkok, the challenge is now greater than 60% full.

The road will join Tao Poon to Rat Burana with a mixture of elevated and underground monitor designed to alleviate congestion within the capital’s dense central districts.

MRTA reported that about 500 m³ of sandbags had been positioned at a diaphragm wall to dam inflows earlier than topping the world with a 3- to 4-m-thick concrete mat and backfilling to stabilize the roadway.

Political scrutiny has intensified as former deputy governor Samart Ratchapolsit accused MRTA of “attempting to dodge duty” and demanded accountability, citing the contractor’s ties to political leaders.

The collapse stems from the difficulties confronted by contractors in underground building in Bangkok’s comfortable alluvial soils and excessive groundwater ranges, the place heavy seasonal rains can additional destabilize the bottom. The Japan Worldwide Cooperation Company has beforehand recognized these as main challenges for increasing the town’s mass transit system.

A peer-reviewed examine revealed in Sustainability in 2022 reached an analogous conclusion, warning that “groundwater pumping has induced long-term settlement within the Bangkok Metropolitan Area, with recorded subsidence charges reaching 10 cm per yr throughout peak extraction within the Nineteen Eighties,” and that gaps in monitoring proceed to depart underground works susceptible.

The incident additionally highlights the vulnerability of station–tunnel interfaces, the cascading influence of utility ruptures, and the reliance on sandbagging and mass concrete as emergency stabilization strategies.

With CKST-PL and MRTA underneath strain to reopen the roadway, questions stay about longer-term impacts on the Purple Line’s supply schedule and whether or not monitoring and oversight had been sufficient earlier than the collapse.