liquefaction

[Balageotech]

Dear Friends,
I have involved in project, where the sub soil till 30m is very poor . SPT N value is 5 to 10 till 30.0m depth. Type of soil is silty sand . We identify that the region more susceptible for liquefaction. Can anybody suggest what is most suitable method of improving the ground and to what depth the improvement to be carried out.

Regards
Bala

 

[Okiryu]

Here in Japan, we normally use sand compaction piles. Local guidelines assume 20m for the depth of influence of liquefaction. At what depth is the water table?

 

[EireChch]

The type of ground improvement and required treatment depth is all specific to your development, .i.e a residential dwelling may only require excavate and replace with hsrdfill to 2m depth where as a 5story commercial building may require soil mixed columns to 8m depth.

You need to supply us with more information to get better feedback. Had there been a liquefaction assessment undertaken?

 

[Balageotech]

Yes, we had assessed the Liquefaction potential. LPI estimated as high.
The proposed construction has multilevel factory manufacturing tower.
vertical load is in the range of 500 to 600 tons.

 

[fattdad]

LQ occurs (typically) within the top 40 ft (12m). Too much confinement below 40 ft.
LQ requires water table conditons. The OP doesn't say anything about the water table.

f-d

¡papá gordo ain’t no madre flaca!

 

[Balageotech]

Thanks all,

The water table is at top surface.

Regards
Bala

 

[EireChch]

Fattdad - I would have to disagree with liquefaction not occurring below 12m. If the soils are soft enough the will liquefy once the increased pore pressure is greater than the effective overburden. Liquefaction can occur to 20m depth. Below this most liquefaction assessment methods (I.e. Idriss and Boullinger) require some refinement.

OP could you explain the structure some more. Is it a tower type building supported on pad foundation? Sorry if I am missing the obvious.

 

[BigH]

EireChch - "soft" enough or "loose" enough?

 

[EireChch]

BigH- thanks for the correction, cohesionless soils so yes I should have said loose enough!

 

[Balageotech]

This is Manufacturing tower , as the soil till 30.0m Is loose deposit we preferred the pile foundation.