1
Kh¸iniÖmvÒ C¬ häc®Êtkh«ngbo
hßav m« hnhhmthÊmGenuchten
GS.NguyÔnC«ngMÉn
PLAXISFINITEELEMENTCODES
2
Kh¸iniÖm vÒ C¬häc®Êtkh«ng boho
LT.ChiÒucao ®íi BHMD
• C¸th¹tth«:hrÊtnhá
• §Êtbôi:hcãthÓ ®¹t2m
• §ÊtsÐt:hcãthÓ ®¹ttrªn20m
TH®Ëp ®Êt
§íikh«ngb+oho,
S¬®åh¹t®Êt B¸nkÝnhmÆtkhum
0,0002cm
0,002cm
0,02cm
TheothÝnghiÖm
§écao d©ngmaodÉnøngvíi c¸c
®−êngkÝnhmÆtkhumkh¸cnhau
(Janssen&Dempsey,1980)
Kh«ng BH:
u
w
v,u
a
Kh«:u=0
BohoMD:u<0
Boho:u>0
+u
Gu
u=γ
γγ
γ
w
.h
w
+h
Gh
(1)
(2)
(3)
(4)
3
Kh¸iniÖm vÒ C¬häc®Êtkh«ng boho
∇
    
σ uw
¸plùc n−íclçrçng d−¬ng
LT¦.ScãhiÖuqu¶
Terzaghi
Fredlund
 
  
σ uwua uw
4
CÊu tróc thnh phÇn cña ®Êt kh«ng boho
§Êt boho(BH)
• §Êt b+oho,chØ
chøa h¹tr¾nv,n−íc:
m«itr−êng 2pha;
• Lç rçng chøa ®Çy
n−íc;
• §éb+oho,:
V
n
/V
r
=1;
• §échøa n−íc thÓ
tÝch:
θ
w
=V
n
/V = V
r
/V =n
• §érçng (n):
n=V
r
/V;
§Êt kh«ng boho(KBH)
• §Êt kh«ng b+oho,chøa
h¹tr¾n,khÝ v,n−íc:
m«itr−êng 3pha;
• Lç rçng chøa c¶khÝ v,
n−íc;
• §éb+oho,:
V
n
/V
r
<1;
• §échøa n−íc thÓ tÝch:
θ
w
=V
n
/V
θ
w
< n
• §érçng (n):
n=V
r
/V;
V
Vn =V
r
V
h
§Êt BH
Vr – thÓ tÝch rçng cñaph©ntè ®Êt
V– tæng thÓ tÝch cñaph©ntè ®Êt
§Êt kh«ng BH
V
k
khÝ
V
n
n−íc
V
h
r¾n
Vr
Vk ≠0
Vn ≠0
Vh ≠0
Vm ≈0
S¬®å
lýthuyÕt
§KBH
khÝ
n−íc
r¾n
mÆt c¨ng
5
MHdßng thÊm trong ®Êt kh«ng boho
T¸c®éng pha khÝ:
nh h−ëng tíi vËn
tèc thÊm;
• MÆt ph©nc¸ch
“N−íc G KhÝ “T¹o
søc c¨ngmÆt
ngoi tronghÖ.
• Pha thø 4.
S
S=1
=1=1
=1
=1
=1=1
=1 1>S>
1>S>S
S
residu
residu
S=
S=S
S
residu
residu
TheoS.LeeBarbour,§HSaskatchewan
SG §éb+oho, residu §éb+oho,d−
KhÝ KhÝ
é b+ohßahiÖuqua
theoV.Genuchten
1〈
−
−
=


