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Yes hopefully driving it on will work without causing any holes and my thought is to by Toyota Fortuna sized covers for a small car so it will go all the way over. The cars are about 2m above the roadway level so hopefully not too much risk of them being completely submerged. Well we'll see soon enough I guess. By the time it gets to more than 2m with us then all the city is going to be under I think.

 

I'm on the TG917 tonight. Hope I make it.

 

Cheers

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After watching, listening, and reading for two weeks, I have reached the following conclusions about the potential for Bangkok to flood:   1. Bangkok is a shallow bowl. It has flood-walls to isola

http://www.theatlantic.com/infocus/2011/10/worst-flooding-in-decades-swamps-thailand/100168/   Some very good photos of the floods here.   I especially like no. 32 and no. 35.

One does not need to imagine the water pressure it is a basic calculation.   1. The Permanent Road / Dykes are designed to carry heavy vehicles, with 3 Meter sandbag walls on top the maximum force a

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You should seriously consider it KS.

 

 

 

A 3 meter high sandbag wall is supposed to be our defense (being build now). 3 meters can you imagine the waterpressure against such a wall! And this 3 meters is on top of a road that was build as a 3 meter dyke. So it is 6 meters of waters pressuring up against such a construction :( ...... I am really pessimistic about such a construction holding it. I would be very happy if it did though.

 

 

 

One does not need to imagine the water pressure it is a basic calculation.

 

1. The Permanent Road / Dykes are designed to carry heavy vehicles, with 3 Meter sandbag walls on top the maximum force at the base of the the structure will be 6 Meter Head of water which equates to 0.6 Bar / 8.8 PSI

 

2. If floodwater was to reach the top of the Sandbags pressure excerpted at the bottom of the temporary structure would be 0.3 Bar / 4.4 PSI and half way up the wall 0.15 Bar / 2.2 PSI.

 

The sandbag structures being built are a joke, same thickness at the base as at the top not tapered as a permeant dyke / dam would be constructed. If failure of a sandbag encasement was to occur it will happen at the base where most pressure is applied and once breakthrough occurs then conditions change from static head to dynamic laminar flow causing the temporary construction to collapse from bottom up.

 

If Sandbags can take the pressure and overflow it is the the same dynamic laminar flow that will cause collapse but from top down.

 

 

Basic Fluid dynamics I learned 30 years ago.

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One does not need to imagine the water pressure it is a basic calculation.

 

1. The Permanent Road / Dykes are designed to carry heavy vehicles, with 3 Meter sandbag walls on top the maximum force at the base of the the structure will be 6 Meter Head of water which equates to 0.6 Bar / 8.8 PSI

 

2. If floodwater was to reach the top of the Sandbags pressure excerpted at the bottom of the temporary structure would be 0.3 Bar / 4.4 PSI and half way up the wall 0.15 Bar / 2.2 PSI.

 

The sandbag structures being built are a joke, same thickness at the base as at the top not tapered as a permeant dyke / dam would be constructed. If failure of a sandbag encasement was to occur it will happen at the base where most pressure is applied and once breakthrough occurs then conditions change from static head to dynamic laminar flow causing the temporary construction to collapse from bottom up.

 

If Sandbags can take the pressure and overflow it is the the same dynamic laminar flow that will cause collapse but from top down.

 

 

Basic Fluid dynamics I learned 30 years ago.

 

 

Thanks for the explanation. thumbup.gif

Even though I know PSI only from my bicycle and I never use it during floodings.

 

So what water level can Wearth's a wall of sandbags withstand?

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Thanks for the explanation. thumbup.gif

Even though I know PSI only from my bicycle and I never use it during floodings.

 

So what water level can Wearth's a wall of sandbags withstand?

 

 

Dependent on number of bags at the base of the wall, average sandbag is 25KG (55 Pounds) and lets say they are 18" wide x 3" tall (when stacked) have a surface area of 54 Square Inches, which mean approx 1 Pound per Square Inch / 1 PSI. So to withstand 3Meters head / 4.4 PSI the wall would have to be 5 Sandbags deep at the base which would withstand 5 PSI, personally I would use at least 6 sandbags at base giving me 135% over design.

 

My wall would be 6 sandbags deep for base 1 Meter, 4 Sandbags for the second Meter and 2 Sandbags for the top 1 Meter. If walls built with only 4 sandbags at the base the pressure at 2.7 meters water level would be > 4 PSI causing wall to fail at the base.

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I've seen sandbag floodwalls through up in the US, and they have always been like an inverted V. What I've seen in LOS look more like a blastwalls we built around the bases of our buildings in RVN to stop mortar shrapnel.

 

.

 

 

Spot on Flash,

 

In a Blast / Explosion be it from artillery, terrorist bomb or and incident in an oil refinery etc the "Pressure wave" dissipates with distance from the epicenter of the source so if the explosion was 50 meters away from the wall at grade level the force at the top of a 5 meter tall structure would only be 10% less than that at grade / base level of the wall, hence the linear design and structure as opposed to the "Inverted V" employed in dams, levees and temporary flood protection.

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Certainly have my own selfish reasons (do NOT want to cancel trip next month), but also for all you folks living and working there, Thai and Farang -- hope this shit subsides and becomes manageable. Following it closely.

 

Best wishes.

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Spot on Flash,

 

In a Blast / Explosion be it from artillery, terrorist bomb or and incident in an oil refinery etc the "Pressure wave" dissipates with distance from the epicenter of the source so if the explosion was 50 meters away from the wall at grade level the force at the top of a 5 meter tall structure would only be 10% less than that at grade / base level of the wall, hence the linear design and structure as opposed to the "Inverted V" employed in dams, levees and temporary flood protection.

 

So, if I understand you correctly, the Thai anti-flood 'blast walls' are only a good solution if the a have sufficient wide base, which would make them very massive, and if so it's actually a waste of sandbags. On the other hand, if the base is too weak those walls would collapse more easily than the traditionally shaped walls of sandbags...

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Correct

 

Level that can he held back is in proportion to the width of the base,

 

So on the assumption that 1 x Sandbag can withstand 1 PSI / 0.0678 Bar / 67.8 CM of water, so to be on the safe side 0.5 Meter.

 

Base of 2 Sandbags for 1.0 Meter

Base of 3 Sandbags for 1.5 Meter

Base of 4 Sandbags for 2.0 Meter

Base of 5 Sandbags for 2.5 Meter

Base of 6 Sandbags for 3.0 Meter

Base of 7 Sandbags for 3.5 Meter

 

etc

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I wouldn't call it a waste if they work, I would call it a waste to use not enough and have it fail, a waste of time and material doing it in the first place. But that's pretty much Thai standard.

 

I would expect them to be almost equilateral triangle in shape, though maybe it's possible to make them slightly more isosceles with a near vertical back wall. Driving back from Nakhon Nayok last week what I saw was a real waste, a single line of sandbags not more than 3 inches high with gaps between them. Not sure what they were supposed to stop.

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