Construction Dewatering as soil improvement? 1

[Silty]

Hi Everyone, if a site with loose saturated sand and silt requires dewatering for construction, can dewatering be considered as a soil improvement method? Can bearing capacity, liquection resistance and soil parameters be increased provided that boreholes are drilled after dewatering to verify?
Please share thought and tips on in what circumstances you consider it appropriate.
Thank you so much

 

[TigerGuy]

I've heard of dewatering being used to assist with pre-construction consolidation. Is it the regular groundwater elevation you are fighting? If so, don't forget what will happen when the pumps are turned off.

 

[EireChch]

While a lower groundwater table does improve bearing capacity, settlement, liquefaction resistance, it cannot be considered as ground improvement.

Like TG said, what happens when the pumps turn off. This is dewatering for construction...

Lowering groundwater is one method to improve slope stability however this is achieved by passive drainage (counterfort drains, horizontal drains etc). Even then there is still some level of gw table considered as we accept that drains will eventually block or partially block and need regular maintenance.

 

[HTURKAK]

Probably negligible improvement . In order dewatering to be considered as a soil improvement method, the dewatering shall be effective for the settleable layer and a consolidation settlement shall be achieved. In this case, the dewatering depth is limited with construction depth. When the pumps turn of, the soil conditions will be similar as previous posters said.

You may look wickdrain to get the concept.

 

[EireChch]

It wont be negligible in terms of bearing capacity anyways, likely 30-40% increase if groundwater is below the failure wedge and you can use the full gamma in the third bearing capacity term.

But regardless its not a good idea as its impractical to keep a site dewatered for the life of a structure and also risky to assume that it will stay dewatered.

 

[PEinc]

Dewatering will make the loose soil heavier which will cause some consolidation and some improvement but how much? When the water level rises to its original level, the soil will not return to its looser, unconsolidated state.

http://www.PeirceEngineering.com

 

[GeoPaveTraffic]

It can be considered ground improvement, but the question is how much improvement will you get versus how much you need?