Stabilisation of alluvial clay 2

[UKENG7]

I wonder if any other members can offer advice?

I am seeking an economic method of increasing the shear strength of alluvial clay before constructing a platform.

Due to the location of the site (Adjacent to a railway), I would rather not go down the temporary works path and infill new engineering material to a suitable depth, thus methods I have considered are Jet Grouting, SoilFrac grouting or piling.

The alluvial clay has a depth of 2.5m.

If anyone has any alternative ideas, I'd be grateful for your views!

 

[Focht3]

Depending on the formation as well as the locally available specialty contractors, you could inject a lime/fly ash slurry to increase the shear strength without disturbing the site much. This may or may not work for you though - how much improvement are you seeking? What are the existing and desired soil properties? We need more in order to be of real help -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[UKENG7]

Thanks Fochts for your reply, the geotechnical report recommended excavating the alluvial clay to a depth of at least 2m and re-filling with an engineering material (Type 1 or similar).
As the proposed foundations for the new platform are only 0.5m away from the rail sleeper ends, I'm very relucant to excavate to this depth for obvious reasons. (Temporary works isn't a popular phrase on the railways!)
The report stated that the soil was weak with a low shear strength and the clay was well above the water table.
I am trying to achieve a shear strength in the soil where-by pad foundations for the new platform can be installed at a relatively shallow depth.
Thanks again.

 

[Focht3]

Shallow piers/caissons/piles are probably a better choice. I'd look at drilled piers, personally - very flexible size and depth. And they can be inspected.

Of course, you may still have a floor/platform settlement issue...depending on how it is designed and constructed.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[dicksewerrat]

Helical screwed in piles and a grade beam would work quite well. You can specify any capacity you need.

 

[ElGreco]

Increase shear strength of alluvial Clay? At first i disagree with any ground improvement techniques mentioned above. Is it worth it to actually spend so much money over 2.5 m of Clay? Secondly, i am not sure about the pile foundations as i dont know exactly the soil profile beneath the clay. However, i am confident that as you are dealing with a rather slurry-soft clay one of thegood actions would be to try and lower tha water table in this 2.5 m. What i would suggest as the most economic solution would be to construct lime/cement columns (i think that is already mentioned). This way you will have an increase in the shear strength of your soil and furthermore lime will react with water and reduce the moisture significantly. Lime columns are very cheap and can be used in such a small thickness. Of course we are talking about in situ mixing which disturbs the environment subtly...good luck

 

[Focht3]

Hmmm,

This is an 'old' thread; posting to it now doesn't help [blue]UKENG7[/blue] much, [blue]ElGreco[/blue] - I'll bet that s/he has made a decision and proceeded with the project since the last post before yours was dated April 5, 2004 (roughly 100 days ago.)

Please re-read the thread - and note that we asked for more information, which was not provided. While your answers may have worked on some sites, some of them aren't particularly appropriate next to a working rail line.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"