Bearing capacity of a high plasticity silt (MH)
Bearing capacity of a high plasticity silt (MH)
(OP)
Hi guys, what would you suggest to use for determing bearing capacity of shallow foundations on a high plasticity silt? The in situ permeability test were about 1E-04 cm/s. Water table is about 4 meters deep.
Would you use drained or undrained analysis? The results from the undrained triaxial tests where fricion angle=27 and cohesion=25 kPa. The undrained resistance is Su/r0=0,3
Thanks for your help.
Would you use drained or undrained analysis? The results from the undrained triaxial tests where fricion angle=27 and cohesion=25 kPa. The undrained resistance is Su/r0=0,3
Thanks for your help.





RE: Bearing capacity of a high plasticity silt (MH)
f-d
ípapß gordo ainÆt no madre flaca!
RE: Bearing capacity of a high plasticity silt (MH)
Dik
RE: Bearing capacity of a high plasticity silt (MH)
RE: Bearing capacity of a high plasticity silt (MH)
f-d
ípapß gordo ainÆt no madre flaca!
RE: Bearing capacity of a high plasticity silt (MH)
Dik
RE: Bearing capacity of a high plasticity silt (MH)
What is your footing width? If the fluctuation of ground water depth is outside of the failure criteria, the undrained parameters may be applicable. Since the soil is MH- a high plasticity silt, an undrained insitu test such as shear vane test may be considered as a design parameter. I believe that the insitu test is less disturbance than the laboratory test. Lok.
RE: Bearing capacity of a high plasticity silt (MH)
http://scholarworks.wmich.edu/cgi/viewcontent.cgi?...
I didn't read the entire thesis, but just looking at the conclusions, appears that the available equations to predict capillary rise for silts underestimate the actual values measured in the lab.
I will also check my notes from Prof. Stark's class. I recall he provided an equation for capillary rise as well.
RE: Bearing capacity of a high plasticity silt (MH)
L0k, im considering a 1x1 m square foundation.
The unconfined compresion test of a not perturbated sample has this results:
-Undrained shear strength, Su: 0,32 kgf/cm2
-Undrained shear strength of remolded sample, Su: 0,89 kgf/cm2
Consolidation test (see attached image)
Tension (kgf/cm2) Void ratio
0 1,472
0 1,478
0,1 1,459
0,25 1,442
0,5 1,425
1 1,399
2 1,352
4 1,276
8 1,176
2 1,184
0,5 1,196
0,1 1,196
0 1,203
2 1,184
0,5 1,196
0,1 1,196
0 1,203
RE: Bearing capacity of a high plasticity silt (MH)
The undisturbed sample will create the the undrained Su > the remoulded strength, it was not happening in your strength where Su=0.32kg/cm2 < Sr=0.89kg/cm2. This showed that your sample is having a certain disturbance, that's why I prefer the in-situ strength. I cannot calculate your ultimate bearing capacity.
Your consolidation test gave the Pc value is about 1.2kgf/cm2. I guess the Po+dp value will be in the elastic condition. So the Cr value will determine your settlement.
RE: Bearing capacity of a high plasticity silt (MH)
Anyways,for your footings which are 1x1 m and assuming that the Df is about 1m, your footings may not be greatly impacting the saturated silts that are at 4 meters below grade (depth of stresses influence for square footings for 10% of stresses at approximately 2B: 2m in your case). So I would use the elastic modulus from your unconfined compressive test and calculate elastic settlements of the silt layer. Again, consolidation settlements may be very small since the stresses for the saturated layer are low.
RE: Bearing capacity of a high plasticity silt (MH)
If there is no notable structure or fabric to the intact soil, then it may be the case that the testing had some issues. Was the remoulded test performed on the same sample with the same density and water content?
RE: Bearing capacity of a high plasticity silt (MH)
RE: Bearing capacity of a high plasticity silt (MH)
RE: Bearing capacity of a high plasticity silt (MH)
The in situ density test gave this results:
Wet density 1,65 t/m3
w% 48,20
Dry density 1,11 t/m3.
The structure is a house with no big loads. What do you think? Remove 2 meters of material and use a structural fill?
Thanks.
RE: Bearing capacity of a high plasticity silt (MH)
pelelo, 2m of overexcavation and structural fill may work but looks expensive for a house. I think that you may be able to work with the soils you have but you need to check settlements and so on. If settlements are too high, try with 1 m of overexcavation and structural fill and see how it goes.