Atterberg Testing

[Hecateh]

Trial holes not good enough for my  structural engineer. 

4 bore holes to 4 metres and then Atterberg testing on the samples - constantly putting the build further out although they have started ground clearance today so we should have a more level playing field so to speak.  Clearing the ground and also diffing the hole for the porosity testing.

I  was told to start with that Atterberg testing on the soil samples takes a week but now they are suggesting it may be closer to a fortnight.  Does anyone know how long the testing takes.  Even googling it isn't helping me

Photo one hour in on ground clearance. They wer here before 8 ready to start at 8 on the dot

[RichS]

I think you are in the same general area as myself, i.e. Yorkshire.

I used White Rose Laboratory Services Ltd in Castleford.

They were very reasonable cost wise, £45.00 + VAT and got the result back to me within 1 week as promised.

I did drop off the sample myself to make things easier but I,m sure you could do the same.

[ToughButterCup]

Attagal! 

(You asked for that )

 

My results came back less than two weeks after the job was done.

But I was comprehensively - though informally - briefed by the geologist at the time.  He could ( just like the piling guy who came along later to inspect the ground) tell almost exactly what the composition was. And, as I later learned, it was almost the same stuff that was found a few hundred yards away. Alluvial Till with Mudstone incursions

[MikeSharp01]

3 hours ago, recoveringacademic said:

incursions

Inclusions or incursions?

[ToughButterCup]

11 hours ago, MikeSharp01 said:

Inclusions or incursions?

 

Incursions I think.  AKA .......annoying inconsistencies .........  One of which nearly caused the piling company to have to cut the probe off at 2 meters  (out of a four meter probe) - at a cost of  a thousand or so quid, (cut off, replace, re-weld, re-pile) while driving the last pile

[Hecateh]

17 hours ago, RichS said:

I think you are in the same general area as myself, i.e. Yorkshire.

I used White Rose Laboratory Services Ltd in Castleford.

They were very reasonable cost wise, £45.00 + VAT and got the result back to me within 1 week as promised.

I did drop off the sample myself to make things easier but I,m sure you could do the same.

Thanks

They have already got the samples - from the company that did the boreholes.  I don't know who the labs are.  The woman at the borehole company told me a week to start with and is now saying could be a fortnight because of what the testing involves - heat and pressure for certain lengths of time.  

 

[Hecateh]

17 hours ago, recoveringacademic said:

Attagal! 

(You asked for that )

 

Yes I've been told informally as well that everything is fine for normal footings but my architect won't budge and do me the drawings until we get the results.  She won't even tell me if she thinks piled footings will be ok or if we are going to need a raft.  We are pretty sure that pilings will be fine.  I think part of the problem is she has told building regs it is a 3 storey building rather than a very small split level that is part one storey and part 2 storey and they have based their demands on that without looking at the drawings.

 

 

[ToughButterCup]

27 minutes ago, Hecateh said:

[...]

She won't even tell me if she thinks piled footings will be ok or if we are going to need a raft. 

[...]

 

Professional indemnity Insurance is  expensive.

Let us know what happens.

Ian

[PeterW]

I thought you had a fixed price and schedule from your builder ..?

 

if so, how has he priced raft vs piles as they are very different beasts ...!

 

And it’s not up to your architect to design this bit unless she is a structural engineer so I would check that too ..!

[RichS]

1 hour ago, Hecateh said:

Thanks

They have already got the samples - from the company that did the boreholes.  I don't know who the labs are.  The woman at the borehole company told me a week to start with and is now saying could be a fortnight because of what the testing involves - heat and pressure for certain lengths of time.  

 

Heat and pressure??

My understanding was that the Atterberg test was a plasticity test so neither of the above needed.

Then again I could have got it wrong

[Hecateh]

Just now, PeterW said:

I thought you had a fixed price and schedule from your builder ..?

 

if so, how has he priced raft vs piles as they are very different beasts ...!

 

And it’s not up to your architect to design this bit unless she is a structural engineer so I would check that too ..!

Thanks. 

It's fixed based on certain assumptions with variables built in for certain aspects that we knew were possible

The architect herself isn't a structural engineer but her partner is and he is doing the calculations, 

 

I love that points are raised on here.  Doing things by myself, I'm trying to keep on top of everything and make sure people have relevant quals and experience but there are so many details it is very easy to miss something and these responses give me a ind of checklist

 

[Hecateh]

3 minutes ago, RichS said:

Heat and pressure??

My understanding was that the Atterberg test was a plasticity test so neither of the above needed.

Then again I could have got it wrong

 

I think you are right, I don't think she knew what was actually being tested and was just telling me the various things that it could be.  

 

So - if it is plasticity. is that something that has to be kept in certain conditions for a period of time?  I wouldn't have thought so.

[PeterW]

Not really - plasticity testing is done to check composition at various levels of water content as certain clays act differently at variable saturation points. 

 

Normally what happens is you get a nice long report stating the components such as sands and clays and it’s compressive strength. 

 

Have you discussed a passive slab with your architect ..? It may be something worth considering if you’ve got to go down the piles/raft route. 

[Hecateh]

37 minutes ago, PeterW said:

Have you discussed a passive slab with your architect ..? It may be something worth considering if you’ve got to go down the piles/raft route. 

 

Passive slab?  Hoping not to have to go down the raft route but would like to know more about this, and it;s benefits.  Do you know of an informative website where I can find out a bit more please?  

[Nickfromwales]

13 minutes ago, Hecateh said:

Do you know of an informative website where I can find out a bit more please? 

??

Your on it ?

@JSHarris blog is very informative from the ground up so maybe check some of his earlier entries and have a damn good read there first. ?

[Jeremy Harris]

1 hour ago, Hecateh said:

 

Passive slab?  Hoping not to have to go down the raft route but would like to know more about this, and it;s benefits.  Do you know of an informative website where I can find out a bit more please?  

 

We have a passive slab, and we're on gault clay.  Essentially it's a way to get a very well insulated, thermal bridge free, foundation system with usually less excavation work and much less concrete used.

 

The idea is an old one, and the basic principle is that if you spread the load imposed by the mass of the house over a wide area then the soil maximum bearing stress can be far lower than for conventional strip foundations, where all the load is taken on narrow strips.  It's a bit like the difference in load that a flat soled shoe will impose on the ground versus a stiletto heel.

 

Without getting in to too much detail. a passive slab relies on a layer of crushed stone to spread the load evenly into the ground, very much like railway ballast stone spreads the load from heavy trains.  If the maximum allowable bearing stress of the soil is very low, then increasing the depth of crushed stone gets around this.  For our hard clay we only needed 150mm of compacted stone, and the insulation was laid on that, with some grit blinding to smooth it, and a 100mm thick reinforced concrete slab was poured into the "tray" made by the insulation.  As an aside, the underfloor heating pipes were also fitted into the slab, as it's very well insulated from the ground beneath and around the edges.  The final benefit was that the slab was poured and power floated dead flat, to exactly the level needed for the final floor finishes, so there was no screeding etc.  It took four days, start to finish, to lay our foundations and slab, with three guys.

 

The bits of interest are here: http://www.mayfly.eu/2013/10/part-sixteen-fun-and-games-in-the-mud/

 

The week after that foundation was put in, the house went up: http://www.mayfly.eu/2013/10/part-seventeen-day-one-of-the-build/  and http://www.mayfly.eu/2013/10/part-eighteen-a-house-in-4-12-days/

 

 

Edited December 5, 2017 by JSHarris
typo

[Calvinmiddle]

And I dug out 750mm of soil then filled it back up with stone before doing my raft.  Much cheaper for me than piling as I have a friend who is a farmer who had access to a 13t excavator and guys on hand to drive grain lorry’s during harvest (in morning waiting for dew to burn off) to take the soil away to fill a hole he had.

 

Know others have done rafts on piles at raft have advantage of being generally better insulated than traditional foundations.

[RichS]

I'm just at the stage of being (almost) ready to pour the concrete for my passive slab.

Similar to @Calvinmiddle I dug out the soil and then put back 150 tons of stone.

All I need now is some decent weather (not freezing) so I can get on with it.

[Gone West]

I had a plasticity test done before I had my PH slab laid. I dug down to the depth of the slab, took a sample, drove over to the labs dropped the sample off and had the results back in a few days. Painless and cheap.