SGM 311 T3 Effective Stress Notes 2020

TEEEEEFivEm
Stressors

, P
σ=
A

Σ F z =0

,
u u P = N + uA

u
,
u P ΣN
= +u
A A
u
,
σ = σ +u

Where:
σ = total stress not same

contact
as

stress

can't measure effective
g- , f
stress in 80M σ = effective stress
30T can measure 0 (w total stress cell )




then : O
'
if
= O
U

-
Lw

u
piesaueter) u = pore water pressure 2

, tEF-EEEE-HESTRES.SN
Cha per 3




✗ Focus on
fully saturated soil
0=_
If
"
"°
above ""



yyertical
on
soil ""
weight +0M ""
→
force ""

external I applies retain
""'s
internal
dam)
=

EFZ 0 '


go.naan.am
=
# contact forces
,

vertical forces embankment
EN

UA water force
'
←
P = EN + UA
external




P=n =
EAI + u
stress
totalcell
cut
element
i
→
-
,

'
I or = O + u o =
total stress

waueg,
not straight '


1 effective
o stress
t -_


to never cut through soil soiid
""
a P" ↳ only cut through contact
surface
U =
pore water pressure
remove
in the internal i
↳ otherwise to include
y bring
have ,
effects stresses of soil particle
, forces) insert

I pieisonreter

* How are stresses distributed

Mag of forces
so that system the static eqllb ↳
Quantifying the internal stresses draw FBD




* interested in vertical component (to keep vertical eqllb W external forces)



•
water pressure in all voids are equal


↳ ie . contribution of water pressure →
force



④ The behavior of soil →
depends on the effective stress

, Van Zyl Spruit Bridge




Total stress cell




3