Pictures courtesy of Daily News

 

Authorities are continuing to fill the sinkhole beneath the Samsen Police Station in Bangkok after the collapse area expanded after heavy rain, raising safety concerns and delaying demolition works. The operation aims to reinforce the weakened ground to allow for safe removal of the damaged building before the next school term begins.

 

At 13:30 on 15 October, Mr. Watcharaphon Kongsawat, Director of Construction Management, reported that teams were still in the process of compacting sand to strengthen the foundation beneath the police station. The filled sand will stabilise the subsurface voids under the structure. Initially, 8,000 cubic metres of sand were planned for the sinkhole, but the volume is now expected to increase due to the widening of the sinkhole, which has grown to a broader cavity following heavy rain. The urgency of the situation is compounded by traffic and time constraints, particularly with the upcoming school reopening.

 

Demolition of the Samsen Police Station building will proceed only once the sand fill reaches the necessary level for stability. Grouting work, cement injection to reinforce soil and sand stability, has been completed in all eight identified sub-surface cavities. In areas where water has accumulated, it is currently being contained and will be pumped out later.

 

Mr. Watcharaphon added that once the sand reaches the required height, sheet piles will be installed on the side facing Sukhothai Road to prevent further soil collapse. Following this, the sand filling will be completed, and demolition will begin. Safety remains the top priority throughout the process. To ensure public safety, temporary road closures will occur in alternating sections during the demolition phase.

 

Mr. Patiwet Herayang, Director of Construction Management Division 4 of the Mass Rapid Transit Authority of Thailand (MRTA), confirmed that contractors have already filled approximately 2,500 cubic metres of sand, achieving a height increase of around two metres, still 4.5 metres below the original road surface. The MRTA continues to monitor and assess the police station, adjacent police flats and nearby buildings to maintain maximum safety.

 

Project officials emphasised that the operation is being carried out with both speed and caution, aiming to restore normal traffic conditions as soon as possible once the ground is stabilised and demolition safely completed.

 

 

Key Takeaways

 

• The Samsen Mai Police Station sinkhole has expanded beyond its original size, prompting additional sand filling.

• More than 8,000 cubic metres of sand will be needed to stabilise the area before demolition begins.

• Authorities aim to finish the work before the school term starts, with safety as the primary concern.

 

Related Stories

 

Samsen-road-remains-closed-as-bma-ensures-ground-stability

 

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

 

 

  Adapted by Asean Now From Dailynews  2025-10-16

 

 

 

 

And next year when the rains come the sand will be washed away...

Wasnt this suppsed to be finished by the 6th

31 minutes ago, Hardcastle P said:

Wasnt this suppsed to be finished by the 6th

right. Oct 6.... but didn't indicate which year.... 

6 hours ago, JoePai said:

And next year when the rains come the sand will be washed away...

 

No Idea about compaction !!    where are the vibrating rollers, plate compactors

Compaction testing is a critical process in civil engineering, ensuring the stability and durability of soil used in construction projects. This test measures the density of soil to verify that it meets the specific requirements for supporting structures such as buildings, roads, and bridges    do they know what a Proctor test is 

It will not only swallow the police station, it will eventually swallow Bangkok as a whole.

 

Time to move the capital again!

18 hours ago, MikeandDow said:

 

No Idea about compaction !!    where are the vibrating rollers, plate compactors

Compaction testing is a critical process in civil engineering, ensuring the stability and durability of soil used in construction projects. This test measures the density of soil to verify that it meets the specific requirements for supporting structures such as buildings, roads, and bridges    do they know what a Proctor test is 

This is Thailand... 

Seems like a quick fix was on the agenda and has been botched 

Now a major job repair needed 

On 10/16/2025 at 7:16 AM, JoePai said:

And next year when the rains come the sand will be washed away...

aka Quick Sand.

21 hours ago, MikeandDow said:

durability of soil used in construction projects

 

In loose, wet conditions, sand can behave like a liquid (quicksand) during an earthquake, causing a catastrophic loss of support strength for a structure. 

Sand's non-cohesive nature means it has a lower inherent bearing capacity compared to other soils, and it can shift or erode easily if not properly contained or reinforced. 

AIGoogle

21 hours ago, MikeandDow said:

 

No Idea about compaction !!    where are the vibrating rollers, plate compactors

Compaction testing is a critical process in civil engineering, ensuring the stability and durability of soil used in construction projects. This test measures the density of soil to verify that it meets the specific requirements for supporting structures such as buildings, roads, and bridges    do they know what a Proctor test is 

I don't know where the pretty graphics come from, but they are grossly misleading. All compacted soil will have some mositure and some air.

32 minutes ago, Srikcir said:

 

In loose, wet conditions, sand can behave like a liquid (quicksand) during an earthquake, causing a catastrophic loss of support strength for a structure. 

Sand's non-cohesive nature means it has a lower inherent bearing capacity compared to other soils, and it can shift or erode easily if not properly contained or reinforced. 

AIGoogle

 

"Sand's non-cohesive nature means it has a lower inherent bearing capacity compared to other soils" is an error of fact. The truth is quite the oppsite. That is yet another example of the risks of believing AI.

22 hours ago, MikeandDow said:

test measures the density of soil to verify that it meets the specific requirements for supporting structures such as buildings, roads, and bridges 

 

you mention SOIL test, but hole is being filled with SAND.

 

soil and sand not same-same.

 

51 minutes ago, Srikcir said:

aka Quick Sand.

 

aka Quick Buck

 

On 10/16/2025 at 5:56 AM, Georgealbert said:

Initially, 8,000 cubic metres of sand were planned for the sinkhole, but the volume is now expected to increase due to the widening of the sinkhole, which has grown to a broader cavity following heavy rain.

 

... O.M.G. ...

... Dumping Loose Sand Into A Sinkhole ... (?)

Trow in also the debris of police building demolition

3 hours ago, Dr B said:

I don't know where the pretty graphics come from, but they are grossly misleading. All compacted soil will have some mositure and some air.

Thats  What a  Proctor test is for  they should be aiming for 95%  compaction in the Proctor test but they will never achieve this Compaction should be done in Layers  Not the way they are doing it  no idea how to fill a hole in numbskull engineering 

Meanwhile, down in the planned SamSen subway station.........

28 minutes ago, MikeandDow said:

Thats  What a  Proctor test is for  they should be aiming for 95%  compaction in the Proctor test but they will never achieve this Compaction should be done in Layers  Not the way they are doing it  no idea how to fill a hole in numbskull engineering 

I know very well what a Proctor Test is for, thank you. You obviously missed my point that all soil, including compacted soil, has voids which are filled with wtaer and air, contrary to what was stated in the graphic. Even most rocks have voids. It is much more efficient, when filling a deep void like this which needs to be done quickly, to just end tip the fill/sand, and then compact it when it is in place.

21 minutes ago, Dr B said:

I know very well what a Proctor Test is for, thank you. You obviously missed my point that all soil, including compacted soil, has voids which are filled with wtaer and air, contrary to what was stated in the graphic. Even most rocks have voids. It is much more efficient, when filling a deep void like this which needs to be done quickly, to just end tip the fill/sand, and then compact it when it is in place.

the examples pics are just that examples   you can not achieve 100% compaction as you stated most compacted soils do have voids  compaction should be done in LAYERS  using D9 dozer and backhoes  will not compact the soil to any meaning full density  vibrating rollers and plate compactors should be used  and compaction when the hole is full will only reach down about 6 to 12 inches in depth not very good for bearing strength THATs why compaction is done in layers to max the bearing strength of the fill  this is 101 in civil engineering  it may be efficient, to just fill the hole then try to compacted it BUT it is not good engineering nor good quality workmanship  

46 minutes ago, MikeandDow said:

the examples pics are just that examples   you can not achieve 100% compaction as you stated most compacted soils do have voids  compaction should be done in LAYERS  using D9 dozer and backhoes  will not compact the soil to any meaning full density  vibrating rollers and plate compactors should be used  and compaction when the hole is full will only reach down about 6 to 12 inches in depth not very good for bearing strength THATs why compaction is done in layers to max the bearing strength of the fill  this is 101 in civil engineering  it may be efficient, to just fill the hole then try to compacted it BUT it is not good engineering nor good quality workmanship  

Try not to make such vehement statements about things of which you obviously have a limited knowledge.

34 minutes ago, Dr B said:

Try not to make such vehement statements about things of which you obviously have a limited knowledge.

Being doing civil engineering for over 25 yrs so i think i know what iam talking about and if you only have snide comments we will end it here 

and why post a picture iam assuming its a grouting rig, not sure what the picture has to do with the current subject more clarification required as this is not the bangkok site 

On 10/16/2025 at 5:56 AM, Georgealbert said:

The filled sand will stabilise the subsurface voids under the structure. Initially, 8,000 cubic metres of sand were planned for the sinkhole, but the volume is now expected to increase due to the widening of the sinkhole, which has grown to a broader cavity following heavy rain.

 

When the story first hit the news, I used their estimated L x W x D numbers and came up with a 45,000 cubic meter hole.

 

My recollection was 30 x 30 x 50 meters, but I see they left out that snippet in the OP.  (maybe someone who's not traveling and has a big screen and keyboard can chime in with their estimate.  It's not worth my effort on a smartphone)

 

I don't think it needs to get bigger for 8000 cubic meters of sand to be insufficient to fill it.

 

14 hours ago, MikeandDow said:

Being doing civil engineering for over 25 yrs so i think i know what iam talking about and if you only have snide comments we will end it here 

and why post a picture iam assuming its a grouting rig, not sure what the picture has to do with the current subject more clarification required as this is not the bangkok site 

Congratulations, but I have been doing civil engineering for over 50 years, in the UK, South East Asia, and Australia, and I am afraid you do not know what you are talking about. The rig is for the compaction of soil over the full depth of the vibrating probe, not for grouting, so is an ideal tool for compacting sand over the depth of the sinkhole. You talked aboiut compaction in layers, but hydraulic fill, which is used for nearly all coastal reclamation sites such as large parts of Singapore and also Laem Chabang and Map Tha Put, is never compacted in layers. I don't expect you to know this, but why do you have to claim to know it all and make snide comments about the Thais and others involved in the Sam Sen backfilling? You were doing much the same about the collapse of the Audit Building, so maybe that is just your style.

14 hours ago, impulse said:

 

When the story first hit the news, I used their estimated L x W x D numbers and came up with a 45,000 cubic meter hole.

 

My recollection was 30 x 30 x 50 meters, but I see they left out that snippet in the OP.  (maybe someone who's not traveling and has a big screen and keyboard can chime in with their estimate.  It's not worth my effort on a smartphone)

 

I don't think it needs to get bigger for 8000 cubic meters of sand to be insufficient to fill it.

 

You are basically correct, and nobody said where the 8,000 cubic metre estimate came from. The hole was never 50 m deep, although that was quoted many times, as the collapsed tunnel which could be seen at the bottom of one early photo (attached) was about 15 to 17 m deep I believe. The cavity was like an inveted cone or pyramid, so the volume is a bit complicated but much less than L x W x D, maybe about 1/3, but still more than 8,000. All of that soil had to go somewhere and must be still there, even though we have not been told about it. Some of it will have gone into the tunnel, but most of it will have flowed into the much larger space inside the station box. We have been told that the authorities did the right thing by choking the hole at the bottom into the collapsed tunnel with concrete, so no more soil could flow into there, which basically means that the cavity cannot get any bigger. It can change shape, with material from the top being washed into the bottom by rain, but the volume remains the same.

The Thais do not have previous experience on this scale, but it has happened numersous times before during tunnelling works. There were comments in earlier threads on this subject to one in South Korea I think, and I know of one in Hong Kong and one in Singapore, and the more famous one at Heathrow Airport many years ago. The normal reaction is to fill up the hole as quickly as possible to stabilise the side slopes, which all have a Factor of Safety of 1 by definition, and then to deal with the additional stabilisation required. This hole has been backfilled more slowly.

21 hours ago, Srikcir said:

aka Quick Sand.

I don't think I will take the underground train when it's finished 

28 minutes ago, Dr B said:

Congratulations, but I have been doing civil engineering for over 50 years, in the UK, South East Asia, and Australia, and I am afraid you do not know what you are talking about. The rig is for the compaction of soil over the full depth of the vibrating probe, not for grouting, so is an ideal tool for compacting sand over the depth of the sinkhole. You talked aboiut compaction in layers, but hydraulic fill, which is used for nearly all coastal reclamation sites such as large parts of Singapore and also Laem Chabang and Map Tha Put, is never compacted in layers. I don't expect you to know this, but why do you have to claim to know it all and make snide comments about the Thais and others involved in the Sam Sen backfilling? You were doing much the same about the collapse of the Audit Building, so maybe that is just your style.

that rig maybe ideal !!Vibratory Probe Compaction (VPC)  BUt it is Not being used in this sink hole  you need to tell the truth not make up stories  about machinery being used  i have never claimed i know it all far from it we learn each day !!   but i do know one thing you are talking rubbish !! When i see bad Engineering and bad quality of workmanship  i will point that out as every one should thats how we learn !! and there is bad engineering and very poor workmanship being done in that sink hole for sure  typical Thai corruption   

Hydraulic fill is a means of selectively emplacing soil or other materials using a stream of water. Hydraulic fill  can be dangerous in areas of seismic activity due to the high susceptibility of the uncompacted, cohesion-less soils in them to liquefaction.  again you are making up story's Thai have no idea what they are doing they are just filling up a hole giving no thought of what is going to happen in the future 

1 hour ago, Dr B said:

Congratulations, but I have been doing civil engineering for over 50 years, in the UK, South East Asia, and Australia, and I am afraid you do not know what you are talking about. The rig is for the compaction of soil over the full depth of the vibrating probe, not for grouting, so is an ideal tool for compacting sand over the depth of the sinkhole. You talked aboiut compaction in layers, but hydraulic fill, which is used for nearly all coastal reclamation sites such as large parts of Singapore and also Laem Chabang and Map Tha Put, is never compacted in layers. I don't expect you to know this, but why do you have to claim to know it all and make snide comments about the Thais and others involved in the Sam Sen backfilling? You were doing much the same about the collapse of the Audit Building, so maybe that is just your style.

Land reclamation is  completely  different ball game than filling a sink hole 

 

standard procedure to fill a sinkhole, you must

first excavate and stabilize the hole, then fill it in layers with large stones, gravel, and soil, compacting each layer as you go. For a strong, permanent repair, especially for larger holes, you may need to use concrete, rebar, and a geotextile fabric to prevent the fill from washing away. 

2 hours ago, MikeandDow said:

Land reclamation is  completely  different ball game than filling a sink hole 

 

standard procedure to fill a sinkhole, you must

first excavate and stabilize the hole, then fill it in layers with large stones, gravel, and soil, compacting each layer as you go. For a strong, permanent repair, especially for larger holes, you may need to use concrete, rebar, and a geotextile fabric to prevent the fill from washing away. 

I apologise. You obviously know far more about this than I could ever hope to. 

Would you be good enough to help me by drawing a cross-section through the sinkhole, about 30 m across at the top and about 17 m deep, and then show me how you would:

1  Excavate and stabilise the hole

2  Fill it with layers of large stones, gravel and soil compacting each layer as you go from the bottom up

3  Where you would place the concrete, rebar and a geotextile fabric

I am eager to learn.

3 hours ago, MikeandDow said:

that rig maybe ideal !!Vibratory Probe Compaction (VPC)  BUt it is Not being used in this sink hole  you need to tell the truth not make up stories  about machinery being used  i have never claimed i know it all far from it we learn each day !!   but i do know one thing you are talking rubbish !! When i see bad Engineering and bad quality of workmanship  i will point that out as every one should thats how we learn !! and there is bad engineering and very poor workmanship being done in that sink hole for sure  typical Thai corruption   

Hydraulic fill is a means of selectively emplacing soil or other materials using a stream of water. Hydraulic fill  can be dangerous in areas of seismic activity due to the high susceptibility of the uncompacted, cohesion-less soils in them to liquefaction.  again you are making up story's Thai have no idea what they are doing they are just filling up a hole giving no thought of what is going to happen in the future 

You were the one saying that it was essential to place the fill and compact in layers. I was showing that there is an alternative.