For sandy material use effective unit weight, for clayey material unit weight "doesn't matter" it's the undrained shear strength Cu or Su that matters.
EireChch,
See attached paper by Ewers & Allman in 2000.
Key conclusion from this paper: "Cα was found to be dependent on the current vertical effective stress and the preconsolidation pressure. The magnitude of Cα was relatively small at pressures below the preconsolidation pressure and...
For global slope stability, a minimum FS of 1.2 may be adopted if there is no sensitive structure/utility nearby. If there is, ground movement/impact on adjacent structure/utility is likely the governing factors, FS may be 1.5 or higher.
Your Ca of 1.2% is likely for normally consolidated soft clay/silt. Natural soil normally has a yield stress/preconsolidation more than its initial effective vertical stress (YSR/OCR > 1.0 depending on its stress history/ageing/cementation etc.), which means without loading the creep rate of...
Drained or undrained conditions is normally related to saturated clays (drained condition is always assumed for sands due to high permeability although fine sand under earthquake can also behave as undrained). For soils above ground water table, unsaturated soil mechanics should be applied.
To...
I have seen on many cases the prediction was way off. So I tend to trust my judgement rather than the driverability analysis done by an inexperienced engineer (GIGO). You need experience & expertise to get it close to reality. Tricky for driven piles terminating in soils, highly variable rock...
To OP, Plaxis is a true 2-D plane strain model while Wallap is a pseudo 2-D model or a subgrade reaction model; which option did you use in Wallap? with soil arching or not? Are you comparing the total strut load or per meter run in two programs? your excavation width? 13m is strut horizontal...
Borehole is a rather crude method for soft clay, I would go CPTu or DMT thru the embankment (predrilling may be required) and in virgin ground nearby (not affected by the embankment load), then compare the yield stress of the soft clay before and after the embankment and work out how much...
human909 (Structural), I referred to the OP' comment below:
"Due to limit in overburden pressure after certain length the increase in length does not contribute much in capacity."
The referenced paper is attached as well...
It's dangerous to adopt this: if a cut slope remains for less than say a year then use short term parameters. I would check both drained and undrained cases if I were you.
If the Cv is very low, and 6 months settlement is still within 60% (DOC<60%), similar settlement is expected at both sites. Otherwise 9m thick clay will settles more than 3m thick clay. Refer to Duncan's 1993 Terzaghi Lecture on limitations of conventional consolidation theory.
100mm for a 7m cantilever, or 1.4% retained height, not appears alarming. How much displacement can the wall take in terms of structural capacity (bending and shear)? Monitoring to see if movement stopped, if not you need to do something about it, either fix the drainage problem or add a lateral...
The following factors to consider:
1. unsaturated clay with suction and/or excess pore pressure due to cutting in saturated clay. 2. For the latter, drained parameters (c',phi')and effective stress (ground water table at long term balanced level) apply when excess pore pressure dissipates to...
There are other pile types: driven cast-in-situ and CFA piles. The OP is after bored piles terminating in soils? The answer could be different for bored piles terminating in rock.
I have similar experience with a highway widening over deep soft clay. Both sides of the highway were widened using surcharge/wick drain preloading, a few cracks as large as 100mm+ were observed along the highway traffic direction. The cracks were filled regularly during preloading then the old...
