Perhitunganlikuifaksiberdasarkan data tanah di daerahLapanganUdaraTabing daerahLapanganUdaraTabing Padang
Gambar1 :LapanganUdaraTabing, Padang
Dengan data tanahterdiridari tanahterdiridari data pengujianSondirdanpengujian pengujianSondirdanpengujian NSPT, terlampir.
PotensiLikuifaksimenggunakan PotensiLikuifaksimenggunakan data pengujianSondir pengujianSondir
1. MagnitudoGempadanPercepatan Tanah Maksimum Untuk data diambildari magnitude gempapadangpariaman 30 September 2009 yakni magnitude 7,6 SR danpercepatantanahmaksimumdiambilsebesar 0,3 g. amax
= 0,30 g x 100 = 300 = 300 x 9,807 m/s 2 = 294,21 gal
2. PotensiLikuifaksi Titik 2
Data :
Estimasiberat volume tanah Estimasidilakukandenganmelihatgrafikyakninilaipenetrasikonus dengan Friction ratio (RF) rata-rata.
(qc)
rata-rata
No Lapisan
:1
KedalamanLapisan
: 100 cm
GWL
: 80 cm
qc
: 42 kg/cm2
Berat Volume
: 0,00185 kg/cm3
Magnitudo
: 7,6 SR
Percepatantanahmaksimum
: 294,21 gal
Gravitasi
: 980,7 cm/s2
* HitungTegangan Total ( 0) = x h
0
= 0,00185 x 100 = 0,185kg/cm2
HitungTeganganEfektif 0
’
= 0- u
= ( x h) – ( w x hw ) = (100x0,00185)-(0,000981x(100-80)) = 0,165kg/cm2
NormalisasaiPerlawananKonus (qc1) qc1
= CN x qc = 1,6 x 42 = 67,2kg/cm2
ReduksiTeganganSiklik (rd) r d =
1,0-0,4113z1,5 +0,04052z+0,001753z1,5 1,0-0,4177z0,5 +0,05729z-0,006205z1,5+0,00121z2
1,5
r d =
1,0-0,4113×1 0,5
1,0-0,4177×1
1,5
+0,04052×1+0,001753×1 1,5
+0,05729×1-0,006205×1
= 0,994
Cyclic Stress Ratio Seed &Idriss
(ag×σ×σ' ) ×r 294, 21×0,185 ) ×0,994 CSR =0,65× ( CSR =0,65×
max
o
d
o
980×0,165
= 0,2169
2
+0,00121×1
TITIK2 PERHITUNGAN LIKUIFAKSI Menghitung Likuifaksi Menggunakan Data Sondir
No titik
2
Layer Number
Depth Range (m)
D ep th ( cm ) q c ( kg /c m2 )
q c1 ( k g/ cm )
CN
ɣ ( kg /c m3)
1
0-1
100
42
67.2
1.6
0.00185
2
1,2-2
200
61
97.6
1.6
0.00185
2.2
2,2
220
165
264
1.6
0.00185
u (k g/cm3)
GWL (cm)
0.01962
0
0.185 80
0.1177 0.13734
rd
’
0
0.16538
ɣ w ( k g/ cm 3) . 0.000981
g ( cm/s2)
a max
C SR
7.6
980
294.21
0.21698
0.37
0.25228
0.987
7.6
980
294.21
0.282475
0.407
0.26966
0.985
7.6
980
294.21
0.290225
TITIK 4 No titik
Layer Number
Depth Range (m)
Depth (cm) qc (kg/cm2)
qc1 (kg/cm)
CN
ɣ (kg/cm3)
1
0-1
100
80
128
1.6
0.0019
2
1.2-2
200
68
108.8
1.6
0.0019
3
2.2-3
300
109
174.4
1.6
0.0019
3,2
3.2
320
175
280
1.6
0.0019
4
ɣw (kg/cm3)
u (kg/cm3)
0.000981
GWL (cm)
0
0
rd
’
Magnitudo g ( cm/ s2) (M)
a max
C SR
0.01962
0.190
0.17038
0.994
7.6
980
294.21
0.216305
0.1177
0.380
0.26228
0.987
7.6
980
294.21
0.279049
0.570
0.35418
0.979
7.6
980
294.21
0.307453
0.608
0.37256
0.973
7.6
980
294.21
0.30986
0.21582
80
0.23544
TITIK 6 No titik
Layer Number
Depth Range (m)
1
0-1
100
2
1.2-2
200
Depth (cm) qc (kg/cm2)
qc1 (kg/cm)
CN
ɣ (kg/cm3)
46
73.6
1.6
0.00195
120
192
1.6
0.00195
6
ɣw (kg/cm3)
u (kg/cm3)
GWL (cm)
0.01962 0.000981
0
0
rd
’
Magnitudo g ( cm/ s2) (M)
a ma x
C SR
0.195
0.17538
0.994
7.6
980
294.21
0.215668
0.39
0.27228
0.987
7.6
980
294.21
0.275874
80 0.1177
TITIK 8 No titik
Layer Number
Depth Range (m)
1
0-1
100
2
1.2-2
3 3.6
Depth (cm) qc (kg/cm2)
qc1 (kg/cm)
CN
ɣ (kg/cm3)
39
62.4
1.6
0.002
200
95
152
1.6
0.002
2.2-3
300
120
192
1.6
0.002
3.6
360
165
264
1.6
0.002
8
ɣw (kg/cm3)
u (kg/cm3)
GWL (cm)
0.01962
0
0
’
rd
Magnitudo g ( cm /s 2) (M)
a m ax
C SR
0.2
0.18038
0.994
7.6
980
294.21
0.215066
0.4
0.28228
0.987
7.6
980
294.21
0.272924
0.21582
0.6
0.38418
0.979
7.6
980
294.21
0.298362
0.27468
0.72
0.44532
0.973
7.6
980
294.21
0.306985
0.1177 0.000981
. .
Magnitudo (M)
0.994
’
80
. . .
. . .
Menentukan Potensi Likuifaksi dari grafik hubungan CSR dan qc1
Gambar :GrafikHubungan CSR dan qc1
Dari grafikdapatdilihatbahwatanahtidakberpotensimengalamilikuifaksidikarenakansebara n data yang beradapadagarisnonlikuifaksi.
PotensiLikuifaksiMenggunakan Data NSPT
Contoh perhitungan: Titik 2
Data NomorLapisan
:1
Kedalamanlapisan
: 200 cm
GWL
: 80 m
N
:6
Berat volume tanah ()
: 0,00195 kg/cm3
Magnitudo (M)
: 7,6 SR
Percepatantanahmaksimum
: 294,21 gal
Tegangan Total (0) = x h
0
= 200 x 0,00195 = 0,39kg/cm2
Teganganefektif 0
’
= 0- u = ( x h) – ( w x hw ) = (200x0,00195)-(0,000981x(200-80)) = 0,272kg/cm2
Reduksitegangansiklik (r d)
, + 0,04052 + 0,001753, 1,0− 0,4113 = 1,0− 0,4177, + 0,05729 − 0,006205, + 0,00121 , + 0,04052 ×1 + 0,001753 × 1, 1,0− 0,4113 × 1 = 1,0 − 0,4177 ×1, + 0,05729 × 1 − 0,006205 × 1, + 0,00121 ×1
= 0,98
Cyclic Stress Ratio Seed &Idriss
× )× = 0,65 ×( × ′ ×0,39) ×0,98 = 0,65× (294,21 980 ×0,2723 = 0,2739
Hitung nilai C N 0
’
= 0,2723 kg/cm2= 27,23 t/m2
C N =
√ ’
C N=
√ ,
C N=0,6060
Hitung nilai (N1)60 (N1)60 = NmC NCECBCR CS (N1)60 = 6.0,606.0,6.1,0.0,8.1,0 = 1,7454
Hitung nilai CRR
50 − 1 + = 34 − 1 + 135 10. + 45 200
7454 + 50 1 = 34 − 1,1 7454 + 1,135 − 10.1,7454 + 45 200 Titik
2
4
Layer Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Depth (cm) 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
NSPT
ɣ
6 13 16 23 41 47 55 60 60 47 48 60 54 60 60 4 11 14 15 34 60 60 60 60 48 45 49 50 60 60
0.00195 0.00195 0.00195 0.00195 0.00195 0.00195 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.00195 0.00195 0.00195 0.00195 0.00195 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018 0.0018
ɣw (kg/cm3)
GWL (cm)
80
0.000981
80
u (kg/cm3) 0.11772 0.31392 0.51012 0.70632 0.90252 1.09872 1.29492 1.49112 1.68732 1.88352 2.07972 2.27592 2.47212 2.66832 2.86452 0.11772 0.31392 0.51012 0.70632 0.90252 1.09872 1.29492 1.49112 1.68732 1.88352 2.07972 2.27592 2.47212 2.66832 2.86452
0
0
0.39 0.78 1.17 1.56 1.95 2.34 2.52 2.88 3.24 3.6 3.96 4.32 4.68 5.04 5.4 0.39 0.78 1.17 1.56 1.95 2.16 2.52 2.88 3.24 3.6 3.96 4.32 4.68 5.04 5.4
’
0.27228 0.46608 0.65988 0.85368 1.04748 1.24128 1.22508 1.38888 1.55268 1.71648 1.88028 2.04408 2.20788 2.37168 2.53548 0.27228 0.46608 0.65988 0.85368 1.04748 1.06128 1.22508 1.38888 1.55268 1.71648 1.88028 2.04408 2.20788 2.37168 2.53548
rd 0.98 0.96 0.94 0.92 0.9 0.84 0.8 0.73 0.68 0.6 0.56 0.5 0.46 0.42 0.38 0.98 0.96 0.94 0.92 0.9 0.84 0.8 0.73 0.68 0.6 0.56 0.5 0.46 0.42 0.38
CN
0.6060 0.4632 0.3893 0.3423 0.3090 0.2838 0.2857 0.2683 0.2538 0.2414 0.2306 0.2212 0.2128 0.2053 0.1986 0.6060 0.4632 0.3893 0.3423 0.3090 0.3070 0.2857 0.2683 0.2538 0.2414 0.2306 0.2212 0.2128 0.2053 0.1986
Magnitudo g (cm/s2) (M)
7.6
980
amax
294.21
CSR (Seed & Idriss) 0.273917 0.313509 0.325232 0.328067 0.326946 0.309008 0.321123 0.29539 0.276896 0.245561 0.230147 0.206206 0.190271 0.174168 0.157929 0.273917 0.313509 0.325232 0.328067 0.326946 0.333617 0.321123 0.29539 0.276896 0.245561 0.230147 0.206206 0.190271 0.174168 0.157929
Soil Description sand sand sand sand sand sand silt s ilt silt silt silt silt silt silt silt sand sand sand sand sand silt silt s ilt silt silt silt silt silt silt silt
Titik
2
4
NSPT
Depth(m)
6
2
13
CSR
(N1)60
FSL
Remarks
0.273917 1.745358 0.051751
5.113036
Nonliquified
4
0.313509 2.890376 0.057709
5.247865
Nonliquified
16
6
0.325232 2.989708 0.058307
5.388307
Nonliquified
23
8
0.328067 3.778518 0.063374
5.000689
Nonliquified
41
10
0.326946 6.080681 0.080326
3.93186
Nonliquified
47
12
0.309008 6.403305 0.082874
3.601879
Nonliquified
55
14
0.321123 7.542611 0.092116
3.367559
Nonliquified
60
16
0.29539 7.727876 0.093651
3.046923
Nonliquified
60
18
0.276896 7.308891 0.090191
2.965719
Nonliquified
47
20
0.245561 5.445274 0.075411
3.14559
Nonliquified
48
22
0.230147 5.313384
0.07441
2.987805
Nonliquified
60
24
0.206206
0.08261
2.41127
Nonliquified
54
26
0.190271 5.516292 0.075953
2.419944
Nonliquified
60
28
0.174168
2.129137
Nonliquified
60
30
0.157929 5.719557 0.077515
1.968136
Nonliquified
4
2
0.273917 1.163572 0.049661
5.328211
Nonliquified
11
4
0.313509 2.445703 0.055172
5.489196
Nonliquified
14
6
0.325232 2.615994 0.056115
5.598734
Nonliquified
15
8
0.328067 2.464251 0.055273
5.733597
Nonliquified
34
10
0.326946 5.042516 0.072376
4.363722
Nonliquified
60
12
0.333617 8.840514 0.103041
3.12762
Nonliquified
60
14
0.321123 8.228303 0.097839
3.170563
Nonliquified
60
16
0.29539 7.727876 0.093651
3.046923
Nonliquified
60
18
0.276896 7.308891 0.090191
2.965719
Nonliquified
48
20
0.245561 5.561131 0.076296
3.109098
Nonliquified
45
22
0.230147 4.981298 0.071921
3.091194
Nonliquified
49
24
0.206206 5.202216 0.073571
2.707499
Nonliquified
50
26
0.190271 5.107678 0.072863
2.522582
Nonliquified
60
28
0.174168
5.91377 0.079021
2.129137
Nonliquified
60
30
0.157929 5.719557 0.077515
1.968136
Nonliquified
6.37006
CRR
MSF
5.91377 0.079021 0.966
Grafik Kedalaman vs Safety Factor
35
30
25
n a 20 m a l a d 15 e K
titik 2 titik 4
10
5
0 0
1
2
3
4
FSL (Safety Factor)
5
6
7
