Picture courtesy of Khaosod

 

A leading structural engineer has outlined four urgent measures to address the severe road subsidence in front of Vajira Hospital in Bangkok, describing it as the largest sinkhole ever recorded in Thailand. The collapse, which occurred on Samsen Road, has forced full traffic closures while emergency repairs are underway. Prime Minister Anutin Charnvirakul inspected the site late on 25 September, emphasising public safety and a rapid restoration of road use.

 

Professor Dr Amorn Pimanmas, President of the Engineering Institute of Thailand and lecturer at Kasetsart University, explained on 26 September that the sinkhole was triggered by three key risk factors: weak soil layers, natural or pipeline water infiltration and underground construction of tunnels and metro stations. He noted that large volumes of soil had shifted into underground structures through weak points, cracks or joints, causing the surface collapse. The professor warned that the incident highlights vulnerabilities in construction on soft soil, where safety margins must be significantly higher.

 

Dr Amorn proposed four corrective actions. First, establish an independent committee of technical experts to quickly identify the cause and publish findings openly. Second, stabilise three key zones, the sinkhole itself, adjacent damaged structures and affected tunnel areas, using appropriate engineering solutions such as structural reinforcement and soil balance monitoring. Third, review and strengthen safety margins in similar construction projects both ongoing and planned. Finally, raise underground construction standards in soft soil areas by installing real-time monitoring and early warning systems to prevent future collapses.

 

The scale of the collapse poses risks beyond the immediate site, with surrounding ground potentially sliding into the cavity and nearby structures at risk of cracking. Heavy rainfall could worsen the problem by loosening soil. Engineers stress that continuous monitoring and urgent reinforcement are needed to prevent further damage.

 

During his inspection, on the evening of 25 September, Prime Minister Anutin was briefed that over 100 cubic metres of concrete had already been poured to seal leaks and stop soil and water ingress into tunnels. He said contractors were working around the clock and expressed confidence that the road surface could be restored within two weeks. He added that about 15,000 cubic metres of soil and gravel would be required to refill the cavity, but assured the public that underground structural repairs would continue alongside surface restoration.

 

The prime minister underlined that his top priority was public safety, directing that all risks, however minor, must be eliminated. He also highlighted that no casualties occurred, calling it fortunate, but stressed that lessons must be learned to prevent future incidents. He confirmed that Samsen Police Station was not in immediate danger.

 

 

Key Takeaways

 

• Expert describes the Vajira Hospital sinkhole may be Thailand’s largest recorded.

• Engineers propose four urgent measures, including stricter safety standards.

• Authorities expect to restore the road surface within two weeks, pending all repairs.

 

Related Stories

 

Massive-road-collapse-near-vajira-hospital-triggers-evacuation

 

Bangkok-sinkhole-battle-sandbags-used-to-halt-collapse

 

 

  Adapted by Asean Now from Khaosod 2025-09-26

 

 

 

 

 

 

The PM says the road will be fixed within a fortnight.....

How about build a large underground parking lot? Just spitballing here....

4 minutes ago, Emdog said:

How about build a large underground parking lot? Just spitballing here....

That would be a perfect idea, but this is Thailand and they will not do it... too conservative thing, no views, and too complicated for them.. but it would be a perfect solution

Safety margins, public safety    nice words but that is all it is!!!    there is NO safety in Thailand, they have the signs but that's all they are signs 

On 9/26/2025 at 10:26 AM, Emdog said:

How about build a large underground parking lot? Just spitballing here....

Better idea would be a fishing pond, think what TAT could do with the revenue 

These are not solutions to the sinkhole,Just the usual soundbites that follow incidents like this

  If safety really was paramount this would not have happened, When cutting a tunnel its relatively easy to measure the amount of soils actually removed, and simple enough to calculate what  the theoretical volume should be.   

  When the first figure greatly exceeds the second there is obviously a serious problem. Work should be stopped and the reasons for the imbalance properly  addressed before work continues

Somebody must have forgot to mention that bit in the health and safety meeting

 

Apparently , at least according to google/ wikipedia  the sinkhole has an area of 900 square meters and is 50 metres deep     900*50=45,000 cubic meters so the estimate of 15,000 is way off the mark, A truck carries around 8 m  of muck    so that's at least   5625 loads required + all the drains and services to repair. plus the original cause of the sinkhole to sort out too. Very ambitious to expect it sorted out in two weeks

I reckon 3 months minimum and possibly a lot longer

On 9/26/2025 at 9:52 AM, Georgealbert said:

First, establish an independent committee of technical experts to quickly identify the cause and publish findings openly.

Should have used experts before digging the tunnels.

As a Non Engineer I would think that the whole problem was created by the tunnel construction  that wasn't strong enough to hold the crappy soil at bay.

Maybe Cheap construction  , cutting costs.

1 hour ago, Bday Prang said:

These are not solutions to the sinkhole,Just the usual soundbites that follow incidents like this

  If safety really was paramount this would not have happened, When cutting a tunnel its relatively easy to measure the amount of soils actually removed, and simple enough to calculate what  the theoretical volume should be.   

  When the first figure greatly exceeds the second there is obviously a serious problem. Work should be stopped and the reasons for the imbalance properly  addressed before work continues

Somebody must have forgot to mention that bit in the health and safety meeting

 

Apparently , at least according to google/ wikipedia  the sinkhole has an area of 900 square meters and is 50 metres deep     900*50=45,000 cubic meters so the estimate of 15,000 is way off the mark, A truck carries around 8 m  of muck    so that's at least   5625 loads required + all the drains and services to repair. plus the original cause of the sinkhole to sort out too. Very ambitious to expect it sorted out in two weeks

I reckon 3 months minimum and possibly a lot longer

How would you fix it?

If you just fix the pipes etc then fill it with concrete, would that work?

28 minutes ago, digger70 said:

As a Non Engineer I would think that the whole problem was created by the tunnel construction  that wasn't strong enough to hold the crappy soil at bay.

Maybe Cheap construction  , cutting costs.

So, the idea that the tunnel construction leaked a bit and a lot of mud seep into it seems a convenient story. 

I have difficulty with that idea because without doing my sums there seems to be a much larger quantity of soil missing from the sink hole than would fill a slightly leaky tunnel.

I think there is a lot more to this than cheap construction etc. Maybe some sort of minor geological event happened un-noticed. 

I'm not a structural engineer either so my guess would be no better than the next mans on here however, the current prime minister has a degree in such matters,

so he's the right person to ask methiks.

4 minutes ago, Muhendis said:

So, the idea that the tunnel construction leaked a bit and a lot of mud seep into it seems a convenient story. 

I have difficulty with that idea because without doing my sums there seems to be a much larger quantity of soil missing from the sink hole than would fill a slightly leaky tunnel.

I think there is a lot more to this than cheap construction etc. Maybe some sort of minor geological event happened un-noticed. 

I'm not a structural engineer either so my guess would be no better than the next mans on here however, the current prime minister has a degree in such matters,

so he's the right person to ask methiks.

Maybe we'll never know .Maybe they can show us first  how much soil they will clean out off the tunnel,If they will tell us the Truth.

4 minutes ago, digger70 said:

Maybe we'll never know .Maybe they can show us first  how much soil they will clean out off the tunnel,If they will tell us the Truth.

Quite so digger. Your meme name seems very appropriate for this story...........🙂

It can even happen in 'nanny states'. Here's the Cologne city center collapse - which had an added Chinese puzzle of a problem.

 

You can easily skip the first three minutes. It shows why these things happen and what the problems of recovery are.

3 hours ago, carlyai said:

How would you fix it?

If you just fix the pipes etc then fill it with concrete, would that work?

fill it with concrete???   45000 cubic meters ?  

5 hours ago, carlyai said:

How would you fix it?

If you just fix the pipes etc then fill it with concrete, would that work?

I have first hand expereince of this in Hong Kong under Hennessy Road on 1 January 1983. The attached photograph shows clearly the subway tunnel has collapsed, and all of the soil will have flowed into that breach. The surface measurements are about 30 x 30 m, but it is not 50 m deep. Other reports suggest two tunnels, with the upper one at about 15 m depth (presumably the one in the photo) and another at about 30 m depth. The weakened soil will have flowed into the empty tunnel and then into the adjacent station box (the other side of the diraphragm wall), which has a large volume. That will have led to road subsidence, seen in some photos with associated rainwater ponding. so the intial tunnel collapse must have been some time ago. The surface subsidence will then have caused the water main to part, and the increased water flow will have exacerbated the situation. The flow into the station box must have been considerable, I estimate > 20,000 m3, so why was it not reported?

Action now should be to choke the hole, with concrete or whatever, then backfill as quickly as possible with all available fill. In Hong Kong this was achieved within 36 hours. Tunnelling through the debris in the hole is the contractor's problem, but they caused it so tough. That will stabilise the Police Station, and get the road open to traffic.

Also note that the contractor this time was Chor Karnchang, and neither Itlaian Thai Development nor Sino-Thai were involved, despite allegations in AN.

17 hours ago, hotchilli said:

Should have used experts before digging the tunnels.

Thaksin can supervise the drainage repairs 

Another idea: develop it as a tourist attraction, such as...

1.Grand Canyon of Thailand

2.Spinoff of Tiger balm gardens: visit hell and check out future accommodation...

3.Journey to the center of the earth them park

4.?

17 hours ago, Muhendis said:

So, the idea that the tunnel construction leaked a bit and a lot of mud seep into it seems a convenient story. 

I have difficulty with that idea because without doing my sums there seems to be a much larger quantity of soil missing from the sink hole than would fill a slightly leaky tunnel.

I think there is a lot more to this than cheap construction etc. Maybe some sort of minor geological event happened un-noticed. 

I'm not a structural engineer either so my guess would be no better than the next mans on here however, the current prime minister has a degree in such matters,

so he's the right person to ask methiks.

Is a  degree in 'such matters' the same as a degree in 'certain things'? 🙂

27 minutes ago, carlyai said:

Is a  degree in 'such matters' the same as a degree in 'certain things'? 🙂

It could be, but I was referring to his academic achievements which are very good.

 

Anutin received his early education at Assumption College in Bangkok before continuing his studies abroad at Worcester Academy in Worcester, Massachusetts, United States. In 1989, he graduated with a Bachelor of Engineering degree from Hofstra University in Hempstead, New York.[5] He later earned a Master of Business Administration degree from the Faculty of Commerce and Accountancy, Thammasat University, in 1990.

Heir to one of Thailand's largest construction fortunes, Anutin inherited close ties to the family-owned company Sino-Thai Engineering and Construction, which has been involved in several major state infrastructure projects, including Suvarnabhumi Airport.[6] Trained as an engineer, he served as managing director of Sino-Thai Engineering and Construction before entering into politics full-time.[7]

Wikipedia

 

 

13 minutes ago, Muhendis said:

It could be, but I was referring to his academic achievements which are very good.

 

Anutin received his early education at Assumption College in Bangkok before continuing his studies abroad at Worcester Academy in Worcester, Massachusetts, United States. In 1989, he graduated with a Bachelor of Engineering degree from Hofstra University in Hempstead, New York.[5] He later earned a Master of Business Administration degree from the Faculty of Commerce and Accountancy, Thammasat University, in 1990.

Heir to one of Thailand's largest construction fortunes, Anutin inherited close ties to the family-owned company Sino-Thai Engineering and Construction, which has been involved in several major state infrastructure projects, including Suvarnabhumi Airport.[6] Trained as an engineer, he served as managing director of Sino-Thai Engineering and Construction before entering into politics full-time.[7]

Wikipedia

 

 

Good to see. I like him even better now.

What about Bentonite? No one mentions this magic.

 

24 minutes ago, carlyai said:

Good to see. I like him even better now.

What about Bentonite? No one mentions this magic.

 

nothing magic about bentonite, its basically just clay

If they are looking for some spare material to fill the whole in with they might consider using the rubble from the recently collapsed sky-scraper,   If there is any left, 

1 hour ago, Bday Prang said:

nothing magic about bentonite, its basically just clay

Swell. 🙂

UPDATE
Samsen Road Sinkhole Repairs on Track for 8 October Completion

 

 

On 9/26/2025 at 9:52 AM, Georgealbert said:

stop soil and water ingress into tunnels.

This is a potential for the entire tunnel length.

What needs to be done is either intercept and remove water reaching the tunnel, ie., underground French drains adjacent to the tunnel and replacing liquefiable soil with non-liquefiable material, and designing underground structures to be resistant to liquefaction effects.

On 9/26/2025 at 11:31 AM, MikeandDow said:

Safety margins, public safety    nice words but that is all it is!!!    there is NO safety in Thailand, they have the signs but that's all they are signs 

Hogwash.

33 minutes ago, Chomper Higgot said:

Hogwash.

Baldadash.

On 9/27/2025 at 5:33 PM, Muhendis said:

Quite so digger. Your meme name seems very appropriate for this story...........🙂

Thank you,   👍

On 9/27/2025 at 2:54 PM, Bday Prang said:

These are not solutions to the sinkhole,Just the usual soundbites that follow incidents like this

  If safety really was paramount this would not have happened, When cutting a tunnel its relatively easy to measure the amount of soils actually removed, and simple enough to calculate what  the theoretical volume should be.   

  When the first figure greatly exceeds the second there is obviously a serious problem. Work should be stopped and the reasons for the imbalance properly  addressed before work continues

Somebody must have forgot to mention that bit in the health and safety meeting

 

Apparently , at least according to google/ wikipedia  the sinkhole has an area of 900 square meters and is 50 metres deep     900*50=45,000 cubic meters so the estimate of 15,000 is way off the mark, A truck carries around 8 m  of muck    so that's at least   5625 loads required + all the drains and services to repair. plus the original cause of the sinkhole to sort out too. Very ambitious to expect it sorted out in two weeks

I reckon 3 months minimum and possibly a lot longer

Compaction required too, otherwise you get a chronic stinkhole.