Tension piles in granular soils?

[BENG_MENG_CENG]

Hi all,

I am looking at a theoretical problem to do with the formation of a basement in granular (dense gravels) the structure is proposed to be approximately 8m below ground level with a high water table at 1m below ground.

As the base of gravels is unproven in the problem a cut off wall is unlikely feasible and such de-watering or ground freezing would be required to allow a ground water free excavation in the temporary case.

In the permenant case however the uplift pressures will need to be resisted and it is not deemed economical to do this via the self-weight of the structure.

In this situation what are the potential options to resist uplift?

- Tension piles via skin friction, are these suitable in granular soils?
- Grouted anchors via engaging a wedge of granular soil, again are these suitable in granular soils?
- Other options?

Thanks.

 

[SlideRuleEra]

In principle, tension piles can resist uplift in granular soils. Geotechnical information down to a considerable depth below ground surface is needed to determine if they are practical for this site.

Dewatering can be accomplished in granular soils, it's just not easy or cheap. The site will have to be dewatered to construct the basement... regardless of how uplift is resisted.

 

[HTURKAK]

You did not provide any info regarding the super structure. If the proposed structure is to be approximately 8m below ground level) The uplift would be 7 tons / sq-m . When you consider the raft foundation, basement slabs , walls , super structure, the uplift pressures could be resisted with the self-weight of the structure. ( just pull down the raft as necessary and provide crushed stone ballast layer )


Another option in this situation to resist uplift is the use of tension piles . Be careful for the watertight connection detail of the pile to the raft concrete .



My opinion..












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