Speeding up the consolidation process 1

[jjsim]

Looking at ways to quicken up the consolidation process of a 20ha land overlain with very soft clay and sand layers with SPN less than 10.

Any novel ideas? I know the conventional way is adding surcharge and installing vertical drains. Any faster way?

 

[Okiryu]

Not a novel method but it is not commonly done:

http://www.ad-hzm.co.jp/trr/hazama/2006/pdf_file/08.PDF

 

[EireChch]

there is a reason surcharge and installing vertical drains is the conventional way. Its probably the best, most economical way...

 

[fattdad]

If you can accurately depict the sand layers you may find you don't even need the vertical drains!

Jam a piezo cone in the ground and see what you can clearly define.

Then I'd calculate the magnitude of consolidation and figure out what U% I'd need to mitigate the problem. Calculate the time for that U% and see whether you need a surcharge?

f-d

ípapß gordo ainÆt no madre flaca!

 

[oldestguy]

I'd run a test fill. You might surprise yourself as compared to running lab consolidation tests. In my experience most recent surcharge jobs take only 1 month max and some only a week per location with a rolling surcharge. These are 10 ft high with 10 ft wide windrow suface.

 

[JHeisenberg]

As you already know, surcharge and drains would be the most common method. Much more expensive but we have used soil mixing techniques to mitigate large settlements when we did not have time to wait for the drains and surcharge to do their thing.

 

[HENRYZAU]

JJ, I would suggest you do CPTu tests and take a few good quality samples for 1-D consolidation tests to have a better understanding of the permeability and yield stress, compressibility. Depending on the outcome and the expected final stress level, you may or may not need surcharge or wicks or both. If test results suggested low Ch and high Cc/1+e0 and low yield stree, and soft clay is thick then both wicks and surcharge is required. If time is the primary concern, and the owner is willing to spend extra to buy time, think about lime column or concrete injection column (CIC).
Good luck
Henry

 

[fattdad]

Just recall that Cv is usually about 2 to 4 times lower than Ch. If there are PVDs the time for consolidation is informed by Ch. You will not get Ch from a consolidation test.

f-d

ípapß gordo ainÆt no madre flaca!

 

[HENRYZAU]

Fattdad, CPTu dissipation test will give a reasonable estimate of Ch. Agree that Cv from oedometer test could be a few times lower than that in the field.

 

[fattdad]

Yes, Henryzau. That was the intent of my first post.

f-d

ípapß gordo ainÆt no madre flaca!

 

[jjsim]

JHeisenberg, what are the soil mixing techniques? Examples?

 

[Okiryu]

We use deep soil mixing as typical soil improvement method..