Earth Pressures & Slide resistance for DSM gravity type wall 1

[BigAEln]

I am involved in the design of a ground improvement behind a quay wall using the deep soil mixing DSM), which is also called Deep Mixing Method (DMM) in Japan. The DSM block behind the quay wall would reduce the earth pressure on the wall. The DSM block is to be founded on stiff to very stiff clay with N> 19, and will have a height of about 20m. Behind the block the clay is very soft to soft becoming firm to stiff with depth. That clay is going to be surcharged by 13m of sand fill, half of which is for land reclamation, and the other half for surcharging. I have the following querries: 1- Given the initial high excess pore water pressure in the clay at the begining of surcharging(du=200 kPa), would the total stress analysis be suitable to assess the earth pressure on this DSM block, despite the initial high pore water pressures in the clay? if not, what else to use and what are the references/publications that support these other choices? 2- Are there design manuals/ design guides, or even previous case histories that recommend the anti slide soil adhesion on the DSM block bottom? I would be very grateful if you could send me replies to these queries or information about useful publications that address them.

 

[dgillette]

I believe you want to start with an undrained analysis (UU) for the initial construction, based on the strengths that exist in the ground before construction, assuming that construction is rapid compared to consolidation. This is the strength you get from VST, CPT, and lab tx or DSS. (Lab tests done at higher confining pressure and projected back to in situ stress and OCR, a la SHANSEP.)

Then, verify that things are OK after PWP dissipation with a drained analysis.


(In general, I try to avoid the terms "total stress analysis" and "effective stress analysis" because of the ambiguity - you can do effective-stress undrained analysis if you model the PWP changes. One exception is doing stability analysis of partially saturated new embankments, where there really is a total-stress strength envelope that varies with total confining pressure.)