For excavation case: 2Bi?^kQ#
Q.fUpa v
1) Clay: low permeability, undrained condition. In this type of soil, 6s>io%,:
NLu[<u U*
for example, in PLAXIS, you can have three options: 9I*2xy|I
JXH f$k
A) analysis in terms of effective stresses (undrained material with E', v', Ta $55K0
c', phi' and psi') P/xE n_*v
uw/N `u
B) analysis in terms of effective stresses with undrained strength .[+}nA,g%~
parameters (undrained material with E', v', but with c_u, phi=0) 4C )sjk?m
jz S iw z
C) analysis in terms of total stresses (material is drained and dry, or non .<Ays?
porous, E_u, v_u, c_u and phi = 0) tN.$4+
?vFtv}@\
If you want to know the detail, please see the PLAXIS MANUAL. m6'9Id-:L
eaDR-g"
2) Sand: drained condition because it has high permeability. The effective poisson's ratio should be input. Cu=0, and phi=some value. Undrained strength for sand should be zero. b7'l3m Qjk
x .$cP
Currently: Hardening soil model can not model the undrained condition for clay(total stress analysis). %{rPA3Xoy
Duncan-Chang model is best model due to the modulus depending on the stress level that is more suitable for excavation and backfill. ttls.~DG
]^8CtgC
Mohr-Coulomb model is quick for trial. The parameters are easy to get and the result can give you overview. I used this model, the results are good compared to the measure data. Dp4x\97O
{-Gh 62hDg
uzT+,
To geofem: ky&wv+7
d|8-# .gV
"对于强透水性土", if the soil is clay, whatever the permeability is high, please use undrained condition, because it is the most unsafe status. If it is sand, use drained condition. o_BRsJy
^"~r/@l
To:daniellb1023: Cm]\5}Py
t|s(V-Wq
"固结不排水": 1)固结, of course it is under drainage. Can you imagine soil can consolidate without water drainage. V`9*_8Dx2
L c
)i
2)不排水, that means the after using confining stress, adding more deviator stress causing failure is under undrained(without pore pressure dissipate)
