Settlement analysis on reclamation area

[sango]

Dear all,

I have a project regarding settlement analysis on reclamation region. The background of the study are:

(1) Continous ground settlement was found over past 15 years. This was reviewed by records of settlement markers (nearest 5 years) and visual inspections on site. Settlement on some locations with thick clay layer can be 1.5m!

(2) The ground conditions were reviewed by current ground invetigation works. A 4.0 to 6.0m of fill layer is overlaying marine clay with thickness varying 8.0 to 15.0m. Below the clay layer, it is alluvium and decomposed rock.

The scope is to find out the settlement is active or not and to advise the amount of residential settlement.

However, my problems are: there is no information on past site formation and ground conditions, and no settlement records since the completion of site formation are available.

By laboratory tests, I determine existing void ratio and existing consolidation parameters. However, initial void ratio, total amount of settlement and initial consolidation parameters are unknown..???

I proposed to carry out vane shear tests to determine current effective stress of clay layer by an empirical formula. (Degree of consolidation = current effective stress / final effective stress) Any comments on this?

Can anyone suggests any information/ journal regarding to this kind of analysis?

 

[Focht3]

A very interesting problem.

Have you carefully studied Chuck Ladd's work in this area at MIT? You really need to read - and understand - SHANSEP as soon as possible (if you have not already done so) before you start working with the in situ vane.

My first impression is that you will have the same problem with strength ratio that you have with initial void ratio (which is what you really want): you don't have good (any?) pre-improvement data.

Have you carefully run consolidation tests on high quality samples from this site? You may be better off using high quality consolidation data and the site history to reconstruct what has probably happened, and what is likely to happen in the future. And this is what you really need to answer the question of whether "consolidation" has stopped.

 

[touma]

I had a somewhat similar project where the fill was marine sand plus miscellaneous fill. The owner had claimed that he had treated the ground both through vibro and dynamic compaction yet we found evidence at the site to the contrary. My only recourse was to go in with a thourough soil investigation with continuous sampling of both cohesive and non conhesive layers and run lab testing from scratch. I feel that this is the only feasible approach especially that in fill/reclaimed area there are always too many unknown to come in and try to add some of our own. I know cost is a factor but in our case it roved to be worth it and for the past 2 years the results have been coming in within the expected. Good Luck.