Bab 9-Kuat Geser Tanah-class 2
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Transcript of Bab 9-Kuat Geser Tanah-class 2
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Kuat Geser Tanah (Shear Strength)
- Triaxial Test -(Courtesy of COSC 323: Soils in Construction)
oleh:
A. Adhe Noor PSH, ST., MTStaf Pengajar Progra Studi Te!ni! Si"il
#urusan Te!ni! $a!ultas Sains dan Te!ni!
%ni&ersitas #enderal Soediran
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Tria'ial Shear Test
Soil sa"le at
failure
$ailure "lane
Porous
stone
i"er&ious
e(rane
Piston )to a""l* de&iatoric stress+
Oring
"edestal
Pers"e'
cell
Cell "ressure
-ac! "ressure Pore "ressure or
&olue change
ater
Soil
sa"le
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Tria'ial Shear Test
Specimen preparation (undisturbed sample)
Sa"ling tu(es
Sa"le e'truder
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Tria'ial Shear Test
Specimen preparation (undisturbed sample)
/dges of the sa"le are
carefull* tried
Setting u" the sa"le in
the tria'ial cell
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Tria'ial Shear Test
Sa"le is co&ered 0ith a
ru((er e(rane and
sealed
Cell is co"letel*
filled 0ith 0ater
Specimen preparation (undisturbed sample)
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Tria'ial Shear TestSpecimen preparation (undisturbed sample)
Pro&ing ring toeasure the
de&iator load
1ial gauge to
easure &ertical
dis"laceent
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T*"es of Tria'ial Tests
s the drainage &al&e o"en
*es no
Consolidated sa"le
%nconsolidated
sa"le
s the drainage &al&e o"en
*es no
1rained
loading
%ndrained
loading
%nder allaround cell "ressure σc
σcσc
σc
σcSte" 4
de&iatoric stress
)∆σ 5 6+
Shearing )loading+
Ste" 2
σc σc
σc7 6
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T*"es of Tria'ial Tests
s the drainage &al&e o"en
*es no
Consolidated sa"le
%nconsolidated sa"le
%nder allaround cell "ressure σc
Ste" 4
s the drainage &al&e o"en
*es no
1rainedloading
%ndrained loading
Shearing )loading+
Ste" 2
C1 test
C% test
%% test
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Consolidated- drained test (CD Test)
Ste" 4: At the end of consolidation
σ8C
σhC
Total, σ 5 Neutral, u /ffecti&e, σ97
Ste" 2: 1uring a'ial stress increase
σ98C 5 σ8C
σ9hC 5 σhC
σ8C 7 ∆σ
σhC
σ98 5 σ8C 7 ∆σ 5 σ94
σ9h 5 σhC 5 σ93
1rainage
1rainage
Ste" 3: At failure
σ8C 7 ∆σf
σhC
σ98f 5 σ8C 7 ∆σf 5 σ94f
σ9hf 5 σhC 5 σ93f 1rainage
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1e&iator stress )6 or ∆σd+ 5 σ4 ; σ3
Consolidated drained test )C1 Test+
σ4 5 σ8C 7 ∆σ
σ3 5 σhC
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8 o l u e c h a
n g e o f t h e
s a " l e
/ ' " a n s i o n
C o " r e s s i o n
Tie
8olue change of sa"le during consolidation
Consolidated drained test )C1 Test+
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1 e & i a t o r s t r e s s ,
∆ σ d
A'ial strain
1ense sand or
OC cla*
(∆σd+f
1ense sand orOC cla*
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C1 tests Ho0 to deterine strength "araeters c and φ
1 e & i a t o r s t r e s
s ,
∆ σ d
A'ial strain
S h e a r
s t r e s s ,
τ
σor σ9
φMohr ; Coulo(
failure en&elo"e
(∆σd+fa
Confining stress 5 σ3a(∆σd+f(
Confining stress 5 σ3(
(∆σd+fc
Confining stress 5 σ3c
σ3c σ4cσ3a σ4a
)∆σd+fa
σ3( σ4(
)∆σd+f(
σ4 5 σ3 7 )∆σd+f
σ3
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C1 tests
Strength "araeters c and φ o(tained fro C1 tests
Since u 5 in C1
tests, σ 5 σ9Therefore, c 5 c9
and φ 5 φ9
cd and φd are usedto denote the
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C1 tests $ailure en&elo"es
S h e a r s t r e s s ,
τ
σor σ9
φdMohr ; Coulo(
failure en&elo"e
σ3a σ4a)∆σd+fa
$or sand and NC Cla*, cd 5
Therefore, one C1 test 0ould (e sufficient to deterine φd of
sand or NC cla*
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C1 tests $ailure en&elo"es
$or OC Cla*, cd =
τ
σor σ9
φ
σ3 σ4)∆σd+f
c
σc
OC NC
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Soe "ractical a""lications of C1 anal*sis for
cla*s
τ τ 5 in situ drained shearstrength
Soft cla*
4. /(an!ent constructed &er* slo0l*, in la*ers o&er a soft cla* de"osit
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Soe "ractical a""lications of C1 anal*sis for
cla*s
2. /arth da 0ith stead* state see"age
τ 5 drained shear strength ofcla* core
τ
Core
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Soe "ractical a""lications of C1 anal*sis for
cla*s
3. /'ca&ation or natural slo"e in cla*
τ 5 n situ drained shear strength
τ
Note: C1 test siulates the long ter condition in the field.
Thus, cd and φd should (e used to e&aluate the longter (eha&ior of soils
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Consolidated- Undrained test (CU Test)
Ste" 4: At the end of consolidation
σ8C
σhC
Total, σ 5 Neutral, u /ffecti&e, σ97
Ste" 2: 1uring a'ial stress increase
σ98C 5 σ8C
σ9hC 5 σhC
σ8C 7 ∆σ
σhC ±∆u
1rainage
Ste" 3: At failure
σ8C 7 ∆σf
σhC
No
drainage
No
drainage
±∆uf
σ98 5 σ8C 7 ∆σ > ∆u 5 σ94
σ9h 5 σhC > ∆u 5 σ93
σ98f 5 σ8C 7 ∆σf > ∆uf 5 σ94f
σ9hf 5 σhC > ∆uf 5 σ93f
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8 o l u e c h a
n g e o f t h e
s a " l e
/ ' " a n s i o n
C o " r e s s i o n
Tie
8olue change of sa"le during consolidation
Consolidated %ndrained test )C% Test+
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1 e
& i a t o r s t r e s s ,
∆ σ d
A'ial strain
1ense sand or
OC cla*
(∆σd+f
1ense sand or
OC cla*
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C% tests Ho0 to deterine strength "araeters c and φ
1 e & i a t o r s t r e s s ,
∆ σ d
A'ial strain
S h e a r s t r e s s ,
τ
σor σ9
(∆σd+f(
Confining stress 5 σ3(
σ3( σ4(σ3a σ4a
)∆σd+fa
φcuMohr ; Coulo( failureen&elo"e in ters of
total stresses
ccu
σ4 5 σ3 7 )∆σd+f
σ3
Total stresses at failure
(∆σd+fa
Confining stress 5 σ3a
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)∆σd+fa
C% tests Ho0 to deterine strength "araeters c and φ
S
h e a r s t r e s s ,
τ
σor σ9σ3( σ4(σ3a σ4a
)∆σd+fa
φcuMohr ; Coulo( failureen&elo"e in ters of
total stresses
ccuσ93( σ94(
σ93a σ94a
Mohr ; Coulo( failure
en&elo"e in ters of
effecti&e stresses
φ9
C9 ufa
uf(
σ94 5 σ3 7 )∆σd+f uf
σ93 5 σ3 uf
/ffecti&e stresses at failure
uf
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C% tests
Strength "araeters c and φ o(tained fro C1 tests
Shear strength
"araeters in ters of
total stresses are ccu and
φcu
Shear strength"araeters in ters of
effecti&e stresses are c9
and φ9
c9 5 cd and φ9 5 φd
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C% tests $ailure en&elo"es
$or sand and NC Cla*, ccu and c9 5
Therefore, one C% test 0ould (e sufficient to deterine φcu
and φ9(5 φd+ of sand or NC cla*
S h e a r s t r e s s ,
τ
σor σ9
φcuMohr ; Coulo( failureen&elo"e in ters oftotal stresses
σ3a σ4a)∆σd+fa
σ3a σ4a
φ9
Mohr ; Coulo( failureen&elo"e in ters of
effecti&e stresses
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Soe "ractical a""lications of C% anal*sis for
cla*s
τ τ 5 in situ undrainedshear strength
Soft cla*
4. /(an!ent constructed ra"idl* o&er a soft cla* de"osit
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Soe "ractical a""lications of C% anal*sis for
cla*s
2. @a"id dra0do0n (ehind an earth da
τ 5 %ndrained shear strengthof cla* core
Coreτ
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Soe "ractical a""lications of C% anal*sis for
cla*s
3. @a"id construction of an e(an!ent on a natural slo"e
Note: Total stress "araeters fro C% test )ccu and φcu+ can (e used for sta(ilit*"ro(les 0here,
Soil ha&e (ecoe full* consolidated and are at e6uili(riu 0ith the
e'isting stress state Then for soe reason additional stresses are
a""lied 6uic!l* 0ith no drainage occurring
τ 5 n situ undrained shear strength
τ
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Unconsolidated- Undrained test (UU Test)
1ata anal*sis
σC 5 σ3
σC 5 σ3No
drainage
nitial s"ecien condition
σ3 7 ∆σd
σ3
No
drainage
S"ecien condition
during shearing
nitial &olue of the sa"le 5 A B H
8olue of the sa"le during shearing 5 A B H
Since the test is conducted under undrained condition,
A B H 5 A B H
A B)H ; ∆H+ 5 A B H
A B)4
; ∆H?H
+ 5 A
z
A A
ε −=
1
0
U lid t d U d i d t t (UU T t)
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Unconsolidated- Undrained test (UU Test)
Ste" 4: ediatel* after sa"ling
5 7
Ste" 2: After a""lication of h*drostatic cell "ressure
∆uc 5 - ∆σ3
σC 5 σ3
σC 5 σ3 ∆uc
σ93 5 σ3 ∆uc
σ93 5 σ3 ∆uc
No
drainage
ncrease of "0" due to
increase of cell "ressure
ncrease of cell "ressure
S!e"ton9s "ore 0ater
"ressure "araeter, -
Note: f soil is full* saturated, then - 5 4 )hence, ∆uc
5 ∆σ3
+
U lid t d U d i d t t (UU T t)
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Unconsolidated- Undrained test (UU Test)
Ste" 3: 1uring a""lication of a'ial load
σ3 7 ∆σd
σ3
No
drainage
σ94 5 σ3 7 ∆σd ; )∆uc > ∆ud +
σ93 5 σ3 ; )∆uc > ∆ud+
∆ud 5 A-∆σd
∆uc > ∆ud
5 7
ncrease of "0" due to increase
of de&iator stress
ncrease of de&iator stress
S!e"ton9s "ore 0ater
"ressure "araeter, A
U lid t d U d i d t t (UU T t)
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Unconsolidated- Undrained test (UU Test)
Co(ining ste"s 2 and 3,
∆uc 5 - ∆σ3 ∆ud 5 A-∆σd
∆u 5 ∆uc 7 ∆ud
Total "ore 0ater "ressure increent at an* stage, ∆u
∆u 5 - ∆σ3 7 A∆σdDS!e"ton9s "ore
0ater "ressure
e6uation∆u 5 - ∆σ3 7 A)∆σ4 ; ∆σ3D
U lid t d U d i d t t (UU T t)
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Unconsolidated- Undrained test (UU Test)
Ste" 4: ediatel* after sa"ling
Total, σ 5 Neutral, u /ffecti&e, σ97
ur
Ste" 2: After a""lication of h*drostatic cell "ressure
σ98 5 ur
σ9h 5 ur
σC
σCu
r
+ ∆uc
5 ur
+ σc
)Sr 5 4E - 5 4+
Ste" 3: 1uring a""lication of a'ial load
σC 7 ∆σ
σC
No
drainage
No
drainageur + σc > ∆u
σ98C 5 σC 7 ur σC 5 ur
σ9h 5 ur
Ste" 3: At failure
σ98 5 σC 7 ∆σ 7 ur σc ∆u
σ9h 5 σC 7 ur σc ∆u
σ9hf 5 σC 7 ur σc ∆uf 5
σ93f
σ98f 5 σC 7 ∆σf 7 ur σc ∆uf 5 σ94f
ur + σc > ∆uf
σC
σC 7 ∆σf Nodrainage
Unconsolidated Undrained test (UU Test)
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Unconsolidated- Undrained test (UU Test)
Total, σ 5 Neutral, u /ffecti&e, σ97Ste" 3: At failure
σ9hf 5 σC 7 ur σc ∆uf 5σ93f
σ98f 5 σC 7 ∆σf 7 ur σc ∆uf 5 σ94f
ur + σc > ∆uf
σCσC 7 ∆σf No
drainage
Mohr circle in ters of effecti&e stresses do not de"end on the cell "ressure.
Therefore, 0e get onl* one Mohr circle in ters of effecti&e stress for different
cell "ressures
τ
σ9σ9
3
σ94∆σf
Unconsolidated Undrained test (UU Test)
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σ3(
σ4(σ3a
σ4a∆σf
σ93
σ94
Unconsolidated- Undrained test (UU Test)
Total, σ 5 Neutral, u /ffecti&e, σ97Ste" 3: At failure
σ9hf 5 σC 7 ur σc ∆uf 5σ93f
σ98f 5 σC 7 ∆σf 7 ur σc ∆uf 5 σ94f
ur + σc > ∆uf
σCσC 7 ∆σf No
drainage
τ
σ or σ9
Mohr circles in ters of total stresses
uau(
$ailure en&elo"e, φu 5
cu
Unconsolidated Undrained test (UU Test)
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σ3( σ1(
Unconsolidated- Undrained test (UU Test)
/ffect of degree of saturation on failure en&elo"e
σ3a σ1aσ3c σ1c
τ
σ or σ9
S F 4E S G 4E
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Soe "ractical a""lications of %% anal*sis for
cla*s
τ τ 5 in situ undrainedshear strength
Soft cla*
4. /(an!ent constructed ra"idl* o&er a soft cla* de"osit
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Soe "ractical a""lications of %% anal*sis for
cla*s
2.
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Soe "ractical a""lications of %% anal*sis for
cla*s
3. $ooting "laced ra"idl* on cla* de"osit
τ 5 n situ undrained shear strength
Note: %% test siulates the short ter condition in the field.
Thus, cu can (e used to anal*e the short ter
(eha&ior of soils
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/'a"le
I Ji&en
; Tria'ial co"ression tests on three s"eciens of a soil sa"le
0ere "erfored. /ach test 0as carried out until the s"ecien
e'"erienced shear failure. The test data are ta(ulated as follo0s:
I @e6uired
; The soil9s cohesion and angle of internal friction
S"ecien
Nu(er
Minor Princi"al Stress
)!i"s?ft2+
1e&iator Stress at $ailure
)!i"s?ft2+
4 4.KK L.
2 2. .L
3 K.32 .L
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/'a"le
S"ecien
Nu(er
Minor Princi"alStress
)!i"s?ft2+
1e&iator Stressat $ailure
)!i"s?ft2+
Major Princi"al
Stress )!i"s?ft2
+
4 4.KK L. .2
2 2. .L .3
3 K.32 .L 44.2
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/'a"le
2 K 4 42 4K
2
K
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/'a"le
2 K 4 42 4K
2
K
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/'a"le
2 K 4 42 4K
2
K
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/'a"le
2 K 4 42 4K
2
K
K
2
2
1
/9.0
26
4
2tan
4
2tan
ft kipc ==
=
=
−
φ
φ
φ
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TH/ /N1