Swelling soil problem 1

[intania]

Hi friends,
I just happened the situation about the soil surrounds the pile footing swelled and it raised the footing 200 mm up from the original level. At the moment I have no idea how to remedy it and I think the footing already loosed from the pile because there are no dowel bars in piles and I think the swelling be the result from ground water. This building is close to the sea (about 5 Km.).
Soil properties in this area be Silty clay to fine sand (CL) about 2.5 m. from ground level and further layer is Clayey fine to medium sand (SC) about 15.0 m. thick and water table is -1.68 m from ground level.
Do anyone have any ideas or how to remedy it, please tell me
Thank you
Intania

 

[ishvaaag]

Respect the foundation part, one can take either the floating solution or the rigid solution, this only if the deeply rooted piles show to undergo what is understood is to be tolerable movement with regard to what there supported. In the floating solution, you design a foundation so rigid that it can support the building above without damage whilst supported in far less points of support than full support, what usually involves general assumption of cantilever work anywhere, and bridging.

It is usual to extend pavements far outwards of the foundation in order to minimize the expansionitself at the building proper. The pavements can still be damaged but the building will be less. However the significant movement and presence of fine sand/silt must be that your foundation may be more difficult to isolate from water input than others, what must also be typical of the places where severe upswell happens under the buildings themselves.

Also consider if the upheave may be being caused by some drinking or sewage water leak or apport.

If the bottom part of the piles goes to depths that do not undergo volume change (for example, are continuously submerged), one can devise through sheats and friable pipe or cover materials the support be coming only from such deep parts, whereas the friction in the section that undergoes volume change passes nil friction due to the scarce strength of the friable material, say, polystirene. The free part is then a column passing the loads.

Other than that you have a present problem on how restore the geometry and load path for your present building. Be a bit more explicit about what your building or structure is and we may be able to give more focused advice on any useful measures. The situation can be as bad as to require a new foundation and then brdge the old building to it.

The book

Practical Foundation Engineering Handbook
Rpobert Wade Brown, editor
Mc Graw Hill

has significant information about soil volume change and foundations.

 

[intania]

Thanks ishvaaag
The piles in this footing have 8.00 m length and I think they are in the swelling soil layer and furthermore, I found the steel structure on this footing be twisted due to swelling soil and the restraint of this steel structure with neighbor structure
Thanks
Intanis

 

[ishvaaag]

If your building is worth enough, you may choose to create an isloated cube of earth through the use of structural or non structural slurry trench walls. You would ensure this way through pavements that the water contents of the soil in such cube around your building remains constant. For the structural trenchwall case, one compressible layer surely would be required, and that's difficult to execute even with a second parallel trench wall excavation. If the apport of water comes through the bottom, these solutions won't work.

An even simpler advice is to look what solutions are being used in the zone, for there you will find condensed what the practical about the case has been found.