Pilings for house, ground too compacted to sink

[kuma]

Good day

Embarking on a house build this week. Day three now and first snag hit...but a concerning one, hoping forum here will have some opinion.

Macro arrived to excavate footing holes. They then took the first piling and using the macro tried to sink it down to bedrock. It would not move even a foot....the ground is incredibly dense (clay) and very compacted. They then it a steel bit on the piling to use to drive it down, again could not make any progress.

Builder now says that given they cannot penetrate the soil to  sink pilings. The solution they offer is to build larger footings (120 wide vs 60) and they will be sunk a total of 240mm under the floor of the house, which is raised 100mm, so 140mm under grade. This they say will support the house (one story, modern roof, qconn brick, just three internal.walls) and no pilings will be sunk, since they cannot penetrate the soil.

Any thoughts from the forum on this issue and the solution? It for sure is a very light structure, but will these larger footings suffice with no pilings?

Thanks in advance for your input.

Cheers

[Crossy]

Where are you?

 

Pushing piles in with a backhoe/makro really isn't satisfactory. If the backhoe can push them in so can your house.

 

If the bedrock really is that shallow then drilled piles would be OK. What do other structures in the same area use?

 

Otherwise driven piles using a proper weight based pile-driver is the correct solution.

 

You need advice from a civil engineer, your local ampur office should be able to point you in the right direction.

 

A really light stucture as you describe would probably be ok on the enlarged footings, but what guarantees are they offering should things start to settle? (do I really need to ask)

 

Note, I'm not a soil/structural engineer so advice is opinion only.

 

 

 

[kuma]

6 minutes ago, Crossy said:

Where are you?

 

Pushing piles in with a backhoe/makro really isn't satisfactory. If the backhoe can push them in so can your house.

 

If the bedrock really is that shallow then drilled piles would be OK. What do other structures in the same area use?

 

Otherwise driven piles using a proper weight based pile-driver is the correct solution.

 

You need advice from a civil engineer, your local ampur office should be able to point you in the right direction.

 

A really light stucture as you describe would probably be ok on the enlarged footings, but what guarantees are they offering should things start to settle? (do I really need to ask)

 

Note, I'm not a soil/structural engineer so advice is opinion only.

 

 

 

Thanks for the reply, appreciate your thoughts, those are pretty much exactly mine.

They say that given the house is very minimal in size and weight, that drilling further to place pilings could be done but the cost is not worth the effort for the stricture. If it was two story or more, red brick and full of rooms with a traditional ceiling it would be different. I understand their point and yes thanks for the tip calling Amphur now to speak with local experts. We are in the south east (Chan) and near a local "mountain" so it is very hard soil.

Here are photos of excavation.

Cheers

 

[singasong]

Bit confused ! first you say "Macro arrived to excavate footing holes" (confirmed by picture) you then say "They then took the first piling and using the macro tried to sink it down to bedrock" I.e.2 different methods,  so what is the method  to be used as per the drawings ?

Edited October 26, 2020 by singasong

[stubuzz]

Is the builder local? If so, he should of known about the soil conditions.

 

Talk to a structural engineer and call another builder.

[kuma]

12 minutes ago, singasong said:

Bit confused ! first you say "Macro arrived to excavate footing holes" (confirmed by picture) you then say "They then took the first piling and using the macro tried to sink it down to bedrock" I.e.2 different methods,  so what is the method  to be used as per the drawings ?

Yea apologies if I am using wrong terminolgy, no expert for sure. Photo of pillars below. They are meant to be sunk below the footings (which are to be placed 140mm below grade) and down to "bedrock" . Footings then would sit on top of those pliiars, then "stilts" would extend up from footings to floor level, which is 100mm above grade, so those stilts would be 240mm in height. Hope this clarifies. But the pillars to the bedrock xannot be sunk , using a macro to push them down (see this being done often in Thailand) so the options are make the footings bigger so they alone support the house, or get a drill/bore machine to come and makes holes to sink pillars. Builder and now also engineers at Tessabn office feel that enlarged footings more than suffice because the ground is very hard and the house is small and light weight enough.

Here ia photo of pilings they were going to sink, but now propose not to.

Cheers

[kuma]

16 minutes ago, stubuzz said:

Is the builder local? If so, he should of known about the soil conditions.

 

Talk to a structural engineer and call another builder.

Not local, Sattahip based, but builds all over. Am bit disappointed that this was not known in advance...but now it seens that this is a project that will be fraught with surprises...lol, very much what I should have expected I guess.

Have spoken to engineers at Tessaban, goung to check with them some more tomorrow. 

The rai here in this area was backfilled and compacted with heavy soil/rock aboit 17 years ago...using a road compactor to compress it. That and 17 years of setyle has made it like concrere it seems.

Cheers

[Chris.B]

10 minutes ago, kuma said:

Not local, Sattahip based, but builds all over. Am bit disappointed that this was not known in advance...but now it seens that this is a project that will be fraught with surprises...lol, very much what I should have expected I guess.

Have spoken to engineers at Tessaban, goung to check with them some more tomorrow. 

The rai here in this area was backfilled and compacted with heavy soil/rock aboit 17 years ago...using a road compactor to compress it. That and 17 years of setyle has made it like concrere it seems.

Cheers

 

For a one storey bungalow, I wouldn't have thought piling was necessary in the first place. 

 

However must be careful here because the op's building terminology is all over the place. <deleted> is a 'macro'! I think he means mecho which is the favorite Thai description for an excavator.

[kuma]

55 minutes ago, Chris.B said:

 

For a one storey bungalow, I wouldn't have thought piling was necessary in the first place. 

 

However must be careful here because the op's building terminology is all over the place. <deleted> is a 'macro'! I think he means mecho which is the favorite Thai description for an excavator.

Lol yes macro, mecho (new spelling for me), commonly called a backhoe in my earlier life...

And yes growing evifence that for structure proposed, sinking pillars may not be necessary

Cheers

[Sharp]

Concrete Stressed piles with the piling machine is the only way TRUST ME !

 

Sometimes the top 1mtr layer may seem tough but can easily be softer underneath.

 

And definalty don't reply on a backhoe to punch/push the piles in.

 

I used the correct machine and piles and over the sq footage of the house the depth ranged from 1.2 mtr to 4.4 mtr in places

[nobodysfriend]

If the ground is too hard to penetrate , just make the foundation holes as large and deep as possible , fill them with steel reinforced concrete , and plant your pillar on it ... that should do it for a small bungalow ... but bring in an expert and have it checked locally is certainly the best advice .

Edited October 27, 2020 by nobodysfriend

[tonray]

Be careful with clay based soil as a base....when very wet....clay softens and shifts position...have to anchor to something that will not change position with shifting seasons. Our property is almost entirely river clay fill.....in dry season...same as you hard as nails...cannot dig more than a few centimeters in....when wet after a few days of rain....turns into massive globs of wet mushy clay 

[Advocate]

Go for the drilled piles. Nothing else provides a decisive, positive result.

 

If house is not on piles then any excavations beside the house after the house is built, or even when the house is built will likely affect the stability of the base soil under the house.

 

My house is on piles, but after 10 years we had a massive subsidence develop beside and under parts of the house and car port due to poor compaction or no compaction for sewage tank excavations and other excavations ten years earlier. We were able to fill the subsidence with sand because our house is on very long piles that were unaffected by the subsidence.

[jojothai]

From the picture of the hole that does not look like clay bedrock. It looks like made ground. The site picture with heaps of soil looks like that. Bedrock clay is solid not grainy.

You need to clean the loose soil out of the base and cut out a chunk of the bed material to see if it is homgenous clay or not. Put it in some water and you will find out. If clay it should stay stiff in one piece and you can pull some off and mold like putty.

Your comments suggest it may be made ground heavily compacted. In that case you need to know how deep.

Before you designed the house best to have diug 4 trial holes at corners up to 1 m deep to check ground. 

Now i suggest that you need to check if the solid layer is very thick or not.  I suggest you first dig one hole deeper. However you can also try to drive in a thick steel pin with a sledgehammer see how far you can drive it in a few locations. Make the pin pointed. Try about a metre long. See how easily it penetrates the ground. If there is a capping layer thats thin you may find out.

Many thai houses are built on what we call rafts, which is what you likely to end up with. A grid of deep beams supporting the floor structure.

These move and can subside if bad ground. Clay swells when it gets wet and causes subsidence. So having clay bedrock may give other problems. Check other buildings around there.

There are other houses in the picture.

One looks more modern.You need to to ask / find out how their foundations were built. Look at local houses for signs of subsidence and any significant cracking in walls. If you see evidence, thats something for an engineer to look at and judge whether you may need to be safer or not drilling for piles.

 

[KannikaP]

17 hours ago, kuma said:

Lol yes macro, mecho (new spelling for me), commonly called a backhoe in my earlier life...

In English it's a digger!

[VocalNeal]

19 hours ago, Chris.B said:

I think he means mecho which is the favorite Thai description for an excavator.

 

It is a local corruption of the North American expression "backhoe".  In UK "JCB" A tractor mounted digging bucket.

Here can also be used to describe an excavator. (trackhoe)

 

Even if you say backhoe in your own dialect it will be understood.

[KannikaP]

3 minutes ago, VocalNeal said:

 

It is a local corruption of the North American expression "backhoe".  In UK "JCB" A tractor mounted digging bucket.

Here can also be used to describe an excavator. (trackhoe)

 

Even if you say backhoe in your own dialect it will be understood.

I do not think people in Lancashire would know what a backhoe was, they'd probably think it was a sex position!

[sometimewoodworker]

21 hours ago, kuma said:

Macro arrived to excavate footing holes. They then took the first piling and using the macro tried to sink it down to bedrock. It would not move even a foot....the ground is incredibly dense (clay) and very compacted. They then it a steel bit on the piling to use to drive it down, again could not make any progress.

You were given bad advice to install pilings, if you did a soil bearing test, which I did, you would find if the soil is sufficient to bear the weight of the house and pad footings, no pilings, would easily be sufficient

 

My house build including the soil bearing test done by a local university professor with his engineering students is in the build story at http://bit.ly/NJnewHouse

 

There is a common misconception that houses need pilings, this is very dependent on soil composition. In Bangkok, because it’s soft mud you absolutely need them, many other places don’t.

 

Two of mine.

Edited October 27, 2020 by sometimewoodworker

[chilly07]

To be safe you need to get a motorized auger/drill to see exactly how deep the  piles need to go- the length of the piles you have purchased should be a guide 

[millymoopoo]

Yep, been through this one before with Thai builders, 2016 Chiang Mai (San Patong).

I wanted a slab, but oh no, 'can't do'...!

Builder wanted 1.2m piles, the other half (who's never built a house before) wanted 2m, straight down into the clay and into the water layer, how smart was that..?

Now the house is cracking up annually as the clay swells and contracts with the seasons.

Thai builders just can't understand that an 'umbrella' slab (150mm slab with 400mm footings around the extremities) floats intact on the clay thus keeping the walls/roof stable, avoiding cracking..!

So easy and cheaper..!

[sometimewoodworker]

44 minutes ago, chilly07 said:

To be safe you need to get a motorized auger/drill to see exactly how deep the  piles need to go- the length of the piles you have purchased should be a guide 

No. A soil bearing test is best, as it’s very likely that the piles are lipstick on a pig. 

[Elkski]

But a soil bearing test will only  test the tip layer.  The op said this is fill 17 ,years ago. We don't know how deep the fill is.  What the underlying soil is. Do we really trust  words that it was compacted?  How throughly if so.   Does time compact well enough.  I dont think a backhoe can install piles correctly.  Max  of it weight.   Need a proper pile driving machine.   Clay does swell and contract.  Good luck.  

[Dragonboat Ronin]

Tempted to say for a 1-story bungalow your likely ok. Personally i prefer to do the job as right as possible from ground up. How long-term are you thinking; is there a possibility of adding 2nd floor in future or increasing building size? Also worth considering how the land on your plot is affected by inevitable changing & flooding conditions. Respect to anyone undertaking challenge of building their own home in Thailand.

[Cake Monster]

Your " Piling Posts " seem to me to not be what you say.

They look in the Photo like the posts used on fencing .

The Posts are put in then a " Panel " of about 5Cm thickness is slid down the slots to form a wall out of them.

My House is not piled. The Foundations are " Pad and Beam " Ie A reinforced Pad 1.4 M Sq x 80cm thick into the ground 1.5 M, and a reinforced Post 80 cm Sq coming off vertically, and all posts locked together with a Beam of Reinforced Concrete 80 x80cm at floor level.

[kuma]

On 10/26/2020 at 1:22 PM, kuma said:

Good day

Embarking on a house build this week. Day three now and first snag hit...but a concerning one, hoping forum here will have some opinion.

Macro arrived to excavate footing holes. They then took the first piling and using the macro tried to sink it down to bedrock. It would not move even a foot....the ground is incredibly dense (clay) and very compacted. They then it a steel bit on the piling to use to drive it down, again could not make any progress.

Builder now says that given they cannot penetrate the soil to  sink pilings. The solution they offer is to build larger footings (120 wide vs 60) and they will be sunk a total of 240mm under the floor of the house, which is raised 100mm, so 140mm under grade. This they say will support the house (one story, modern roof, qconn brick, just three internal.walls) and no pilings will be sunk, since they cannot penetrate the soil.

Any thoughts from the forum on this issue and the solution? It for sure is a very light structure, but will these larger footings suffice with no pilings?

Thanks in advance for your input.

Cheers

Quick thanks to all for taking the time to reply, lots of great information shared. Been offline all day, will work on replies/updates tonight, cheers.

[misterphil]

On 10/26/2020 at 8:45 AM, Chris.B said:

 

For a one storey bungalow, I wouldn't have thought piling was necessary in the first place. 

 

However must be careful here because the op's building terminology is all over the place. <deleted> is a 'macro'! I think he means mecho which is the favorite Thai description for an excavator.

Macro is Thai for Back Hoe

[kuma]

15 hours ago, Sharp said:

Concrete Stressed piles with the piling machine is the only way TRUST ME !

 

Sometimes the top 1mtr layer may seem tough but can easily be softer underneath.

 

And definalty don't reply on a backhoe to punch/push the piles in.

 

I used the correct machine and piles and over the sq footage of the house the depth ranged from 1.2 mtr to 4.4 mtr in places

At this point have excavated down to 1.5M, which is where the footings will sit. It was from there that they attempted to drive the pillars in, and they did not budge....for sure the soil is rock hard, and not anything like on the attached - good bit of humour I found in all of this lol

Cheers, thanks

 

 

[kuma]

15 hours ago, nobodysfriend said:

If the ground is too hard to penetrate , just make the foundation holes as large and deep as possible , fill them with steel reinforced concrete , and plant your pillar on it ... that should do it for a small bungalow ... but bring in an expert and have it checked locally is certainly the best advice .

Good day, thanks for that. Yes I spoke with the engineer at the Tessaban and they also suggested pilings were overkill for the structure we are building. The footings were to be 0.8 x 0.8 m of reinforced concrete but now they plan to expand them to 1.2 x 1.2m to give additional support. There are nine footings for a house of only 42sqm and the walls are Q-Conn, which is very light, plus the roof is modern style so again light weight. I did decide to build a small place first, to see how things would go - and wow so far happy I did that. 

Pondering calling up a local engineer to get their input, but wonder if it will be $ well spent?

Cheers

[kuma]

14 hours ago, Advocate said:

Go for the drilled piles. Nothing else provides a decisive, positive result.

 

If house is not on piles then any excavations beside the house after the house is built, or even when the house is built will likely affect the stability of the base soil under the house.

 

My house is on piles, but after 10 years we had a massive subsidence develop beside and under parts of the house and car port due to poor compaction or no compaction for sewage tank excavations and other excavations ten years earlier. We were able to fill the subsidence with sand because our house is on very long piles that were unaffected by the subsidence.

Thanks. I hear you about nearby excavations. I will ask them about this. On one side someone could excavate about 6-7M nearby. that is as close as any work could get - unless I decided to do more.

Cheers

[kuma]

14 hours ago, jojothai said:

From the picture of the hole that does not look like clay bedrock. It looks like made ground. The site picture with heaps of soil looks like that. Bedrock clay is solid not grainy.

You need to clean the loose soil out of the base and cut out a chunk of the bed material to see if it is homgenous clay or not. Put it in some water and you will find out. If clay it should stay stiff in one piece and you can pull some off and mold like putty.

Your comments suggest it may be made ground heavily compacted. In that case you need to know how deep.

Before you designed the house best to have diug 4 trial holes at corners up to 1 m deep to check ground. 

Now i suggest that you need to check if the solid layer is very thick or not.  I suggest you first dig one hole deeper. However you can also try to drive in a thick steel pin with a sledgehammer see how far you can drive it in a few locations. Make the pin pointed. Try about a metre long. See how easily it penetrates the ground. If there is a capping layer thats thin you may find out.

Many thai houses are built on what we call rafts, which is what you likely to end up with. A grid of deep beams supporting the floor structure.

These move and can subside if bad ground. Clay swells when it gets wet and causes subsidence. So having clay bedrock may give other problems. Check other buildings around there.

There are other houses in the picture.

One looks more modern.You need to to ask / find out how their foundations were built. Look at local houses for signs of subsidence and any significant cracking in walls. If you see evidence, thats something for an engineer to look at and judge whether you may need to be safer or not drilling for piles.

 

Excellent post, really appreciate you taking the time. Indeed I think I have not identified the soil correctly when I say clay; clay is more like the soil in the You Tube video link I posted above. 

This structure is one story, 42 sqm, with only three interior walls, 1 x 4m, 2 x 3m. All walls interior and exterior are qconn brick, windows and doors will be upvc - there are actually seven windows and a 200mm sliding door plus a 80cm man door, those might be heavier than the walls lol.

I will walk with the builder tomorrow and see the other homes nearby. This land, according to locals, was filled in with soil almost 20 years ago, and compacted with a highway earth compactor. We have excavated almost 2m down now, and from there they tried driving the pillars in - but they would not penetrate the soil, even with a steel bit added to the tip.

Appreciate the input, cheers