what's the best method?

[chadegani]

HI

WE HAVE THE PETROCHEMICAL PLANT AND HEAVY EQIPMENT IN IT, SOIL STRATIFICATION CONSISTING VERY WEAK CL (LOW PLASTIC CLAY WITH SOME SAND LENSES ), WE HAVE STIFF LAYER IN DEPTH 22 m. & WATER ELEVATION IS 1 METER BELOW G.EL.

WHAT'S THE BEST METHOD FOR SOIL IMPROVING (EXCEPT PILE) IN THIS STATE.

 

[dik]

You need a real good geotekkie... your soil conditions are really poor. You might try to excavate a portion of the overburden and use a compacted granular layer to help distribute loads. You also might try a raft type foundation. In any event, you need a real good soils guy.

Dik

 

[VAD]

Dik has provided sound advice re soliciting a geotech. A good problem for structural and geotech to work on together. Configuration loads etc from structural, analysis of existiong conditions re loads etc from geotech with possible remedial measures etc. Just like going to the medic.

In addition to measures provided by Dik,another possible approach is the use of stone columns. However, more info is needed before anyone can provide adequate solutions but not without doing some number crunching.

 

[DRC1]

Why not piles?

 

[dik]

unsupported length?

 

[chadegani]

Hi dik

if I understand your question correctley , my pile caps usually seated on grade and according to parctical formula my unsupported length below grade are 4 m( for pile 40*40 ).

 

[DRC1]

Generally even weak soils will provide lateral support unless it is complete glop. Liquifaction is also a consideration dring a seismic event. I am not familar with the formula you are using. However, if you are concerned about unsupported length, Piles can be designed fo 4 meters of unsuported length. Good choices to investigate would be concrete filled pipe or monotube. Others may work also.

 

[krepus]

if you have sufficient time, consider preloading to eleminate portion of the long term settlement...

 

[Prepakt1]

Compaction Grouting is one possible method.Grout is injected by grout sleeves(Manchette Tubes} at high pressure to form concrete bulbs at different levels in the soil. The pressure of the concrete compacts the ground and increases the ability of the soil to carry heavy loads.This can be done under existing equipment but you should still use a geotech to evaluate the probable outcome. We were recently looking at doing this under a dock container railway that was sinking .This method should carry the type of loading that you require .

Intrusion Prepakt

http://www.marineconcrete.com

 

[dik]

Franki piles?

Dik

 

[rchanke]

In soil profiles with weak and/or sensitive clays installation of stone columns or compaction grout columns may not be best suited due to their installation technique (full displacement). Both stone columns and compaction grouting will initiate remolding. Furthermore, stone columns require a given amount of lateral confinement in order to accept and transfer axial load.

Cement-Soil mixing is often better suited for these types of sites. In addition to addressing static bearing requirements, soil mixed columns can be placed in a cellular formation to assist in mitigating liquefaction potential. A few feet of granular fill together with geotextile make for a good load transfer mattress on top of the soil mixed columns. This ground modification system has been used successfully on several tank farms in the southern US.