Staged Construction of Embankment on Soft Clay


Hi all,

Currently, I am working on a design and staged construction of embankments on soft clay. We would like to construct embankment and install PVDs to achive designed platform level and speed up the consolidation rate. There are spun piles directly next to the future embankments. In order to ensure the deformation of the piles is below the allowable tolerance, we would like to place the fill in stages.

I would like to ask some questions which are as follows:

1. Undrained strength Analysis ( cu ≠ 0; φu = 0)

I would like to use undrained parameters for stability analysis. The first fill height is limitted to that which has a factor of safety that is equal to or greater than the minimum acceptable interim value (FS = 1.15 t0 1.2). This initial fill height is used as a starting point. Then, I allow the the soil to settle for a period of time so that the soil will gain the the undrained shear strength (

Δcu).

  • Could you help me to elaborate more detail about how to estimate the gain in Δcu ? 
  • I am looking for some references discussing about the increase in Δcu such as those written by Ladd or other experts. Could you please share some references so that I can study them in detail ?

2. Calculating the deformation of the piles

I would like to model the piles in PLAXIS 2D ( this is the only software that I am familiar with). How do I model the piles so that the piles behaviour is a pile row? 

Are there any ways to estimate the deformation of the piles? Could you please share to me.

Thank you for your help

 

 

Soil Mechanics / Geotechnical Design Construction Ground Improvement Landslides - Slope Stability Analysis

Asked 29/12/2014 05:15, updated: 14/03/2017 10:08
Alex

Not what you were looking for?


Ask Plaxis Experts!

More on Plaxis


News Questions

4 Answers

Votes: 0

Scott Andrew Barnhill

There is a method from -  Soil Improvement By Preloading, Stamatopoulos & Kotzias, pp. 155-159


Votes: 0

Myint Win Bo

I would advise to read two books I have written based on actual project works carried out under multi billion $ projects.

1) Soil Improvement, Prefabricated Vertical Drain Technique

2) Reclamation and Ground Improvement

 

Dr Myint Win Bo


Votes: 0

Jeffrey A Farrar

A good paper od soft ground site characterization.  Ladd also has done many research programs on staged construction.  I recall one in the 70's with ASCE where they built a staged embankment and had everyone try to predict the failure!  So you might Gooogle Charles Ladd MIT.  He recently passed away...will be greatly missed.

Ladd, C.C., and D.J., DeGroot, “Recommended Practice for Soft Ground Site Characterization: Arthur Casagrande Lecture,” 12th Pan-American Conference on Soil Mechanics and Geotechnical Engineering,  Massachusetts Institute of Technology, Cambridge, MA, June 22-25, 2003, revised May 9 2004


Votes: 0

Geodomisi Ltd - Dr. C. Sachpazis

1) The simplest and the most accurate way to estimate the strength increase in Δcu is to make a investigation and sampling borehole and extract some undisturbed samples and then make U-U and C-U triaxial tests. By this way you can have a real reading of the Cu change with time.... Certainly you can simulate the whole procedure by FEA programmes, but this could be tricky.... Dr. C. Sachpazis.

2) Calculating the deformation of the piles is easier performed by Rocscience suite (Phase2) @ https://www.rocscience.com.