Pilings for house, ground too compacted to sink

[kuma 148]

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 27,211]

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 148]

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 24]

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 1,286]

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

 

Talk to a structural engineer and call another builder.

[kuma 148]

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 148]

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 118]

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 148]

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 1,977]

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 4,231]

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 13,450]

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 93]

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 517]

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 650]

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!