Pilings used as soil stabilization
Pilings used as soil stabilization
(OP)
Does anyone have any experience with a design method using piles as a means of soil stabilization? Is it recognized in any codes?
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Pilings used as soil stabilization
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Pilings used as soil stabilizationPilings used as soil stabilization(OP)
Does anyone have any experience with a design method using piles as a means of soil stabilization? Is it recognized in any codes?
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RE: Pilings used as soil stabilization
One thing is for certain: The design loads and structural demands can be huge, and other methods should be considered. Drainage galleries can be effective if ground pore pressures are an issue.
Assuming we are back to piles, here is one method I have used successfully (which means I may have been too conservative?):
Slope stability analysis to calculate the unbalanced force required per pile to achieve an adeqaute factor of safety against slope failure. Use L-Pile to determine the unfactored shear and moments on the piles for some accepted deflection. Consider factoring the shear and moments and design the piles using the building code requirements for deep foundations.
Better yet, but perhaps too sophisticated: do a coupled analysis with the piles and ground in a model - like a finite element model. This should be done only by a geotechnical engineer with numerical modeling experience, or time and budget to get experienced.
RE: Pilings used as soil stabilization
RE: Pilings used as soil stabilization
Drilled shafts are not a very economical means of remediaing a slide, drainage, grade changes, rock buttress are all generally cheaper and quicker to install. However, in both cases, for very different reasons, none of these would work.
One of the systems was 48-inch diameter shafts installed at 8-foot centers. The other one was 36-inch diameter shafts installed at 7-foot centers.
RE: Pilings used as soil stabilization
RE: Pilings used as soil stabilization
As for use in structures, we did look at using them or something similar on a project where we were looking to improve the performance of PFA Lagoons, with the idea that the lime could act as a catalyst and aid the stabilisation of the PFA. However no Contractor was willing to put their name to it so it never got past the Blue Sky thinking phase and on to the drawing board, never mind off of it!
Other than that, back in the early 90's we did use augered columns of lime as a means of pre-treating soil with the binder, before excavation and stockpiling. This was done in this manner as the bulk soils were required to be stored for around 18 months before use, and there was a risk of sulfate attack. The lime was added in this manner, soils excavated (which mixed the lime throughout the soil) and stockpiled with the sulfate and lime left to react. 18 months later checks carried out to see if there was any future potential expansion, and when the soils were cleared, they were re-engineered back in as 'modified' soils (not stabilised).
There has not been much use of this type of technique, probably because not only is it relatively unproven, but simiar ground improvement methods, such as vibro-stone or vibro-concrete are not much more expensive, have less risk (sulfate attack) and have been used for a long time (civil engineering can be conservative)
One thing to note if you are considering this, is to get a complete vertical profile of the sulfates in the ground, and in particular between the weathered and unweathered zones.
RE: Pilings used as soil stabilization
RE: Pilings used as soil stabilization
If modest, they can be counted as piles for what they are worth.
We are talking of very old traditions of foundations, coming from palafitos maybe even through amphora: always trying to regularize strength.