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DEALING WITH EXPANSIVESOIL
R. Karlinasari
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TUJUAN :2
Tujuan dilakukannya kajian topik ini adalah :
Mempelajari cara-cara melakukan site
characterization pada tanah ekspansif.
Mempelajari cara-cara identifikasi dan klasifikasitanah ekspansif
Mempelajari pendekatan unsaturated soil untuk
menjelaskan karakteristik tanah ekspansif.
KESIMPULAN
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Case: Expansive Soils @ Cikarang
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Expansive Soils Damages
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Expansive Soils Damages
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Expansive Soils Damages
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Expansive Soils Damages
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KARAKTERISASI LAPANGAN8
SkemaKarakterisasi
Lapangan, Nelson
& Miller, 1992
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KARAKTERISASI LAPANGAN
PROPERTIS TANAH
KONDISI LINGKUNGAN
KONDISI STRESS STATE
9
FAKTOR-FAKTOR BERPENGARUH,
MENGAKIBATKAN KEMBANG DAN SUSUT
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PROPERTIS TANAH10
Faktor Clay Mineralogy
Soil Water Chemistry
Soil Suction
Plasticity
Soil Structure and Fabric
Dry density
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KONDISI LINGKUNGAN11
Initial Moisture Condition
Moisture variations
Climate
Groundwater
Drainage and manmade water sources
Vegetation
Permeability
Temperature
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KONDISI STRESS STATE
12
Stress history
Insitu initial stress state
Loading
Soil Profile
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Why Do Clays Expand and Shrink ?
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Clay Mineralogy14
Sheet pada mineral group Kaolinite, Illite dan Montmorilonit (Budhu,2000)
Perbandingan Kandungan Kimia
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CLAY MINERAL STRUCTURE
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MECHANISM OF SWELL
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MECHANISM OF SWELL
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MECHANISM OF SWELL
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MECHANISM OF SWELL
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Scanning Electron Microscope
Laboratory at TEKMIRA Bandung
Capabilities
Identifying minerals, rock and
other materials served in
nanno size. Available analyses
are photomicrograph, spot, line
and x-ray mapping analyses.
Facilities
Scanning Electron Microscope
(SEM) JEOL JSM-6360-LA.
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Kaolinite23
Grup Mineral Kaolonite (Named from Kao-Ling, China Scale: Picture size 50
microns)(http://www.omnilabs.com/)
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Illite24
Grup Mineral Illite (Named from Illinois,US) Scale: Picture size : 33 micron
(http://www.omnilabs.com/)
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Montmorilonit25
Grup Mineral Montmorilonite , Named from : Montmorillone, France Picture
size : 67 micron (http://www.omnilabs.com/)
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Karakteristik Properti
Psyco-Chemical Mineral27
Isomorphous substitutionSi dan Al dapat digantikan sebagian oleh atom lain dengan ukuran yang
sama. Substitusi oleh atom pada nilai valence yang lebih rendah
menghasilkan secara netto suatu negative surface charge. Jika derajat
substitusi lebih besar maka akan menghasilkan surface charge yang lebih
besar pula.
Substitusi yang umum :
Si4+diganti oleh Al3+ pada silica sheet
Al3+ diganti oleh Mg2+ pada octahedral sheet
Molekul air adalah strong dipole (2H+, O2-). Molekul air dapat disejajarkanpada suatu medal electric dan menarik ions yang berada dalam campuran
(solution). Akibat isomorphous substitution water molekul air ditarik dan
dihisap dengan keras pada clay particle surfaces. Air yang teradsorbsi
mengurangi lebarnya diameter throat (leher) pori yang tersedia untuk air
yang bebas
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Karakteristik Properti
Psyco-Chemical Mineral 229
Diffused Double Layer Mineral
Permukaan lempung yang memiliki negative charged akan menarik kation
dan menolak anion. Charged surface
(EDL) dan distribusi charge pada fase cair DL dikenal dengan nama DiffuseDouble Layer DDL
DDL model memungkinkan dilakukannya komputasi dari electrical
potential,, sebagai fungsi dari jarak dari charged particle surface.
Model yang diusulkan oleh Gouy (1910) and Chapman (1913), dankemudian di modifikasi oleh Stern (1924)
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Diffused Double Layer Mineral
Mekanisme DDL (Budhu,2000)
30
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Atteberg Limit
Mineral ActivityKaolinite 0.33 0.46
Illite 0.9
Montmorilonite (Ca) 1.5
Montmorilonite (Na) 7.2
m2finer thanby weight%
IndexPlasticity)Ac(Activity
m
40
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Cation Exchange Capacity
CEC adalah kapasitas pertukaran kation yang diperlukan untuk menyeimbangkan arusnegatif pada permukaan partikel lempung. CEC diukur dalam sejumlah milliequivalentper 100 gram dari lempung kering.
Clay Mineral CEC (meq / 100g)
Kaolinite 3 15
Illite 10 40
Montmorilonite 80 150
41
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Potential Volume Change Meter
42
PVC meter tanah adalah suatu alat yang standar untuk mengukur swelling pressure
dari suatu tanah yang terkompaksi. PVC meter dapat digunakan di lapangan maupun di
laboratorium. Pengujian dilakukan dengan meletakkan suatu sample yang teremas
dalam ring alat konsolidasi dengan suatu gaya pemadatan Proctor yang dimodifikasi
dari 55000 ft-lb/ft3 (2600 kJ/m3) pada kadar air naturalnya
Swell Index versus PVC (Lambe, 1960)
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Expansion Index Test
43
EI ExpansionPotential
0-20 Very Low
21-50 Low
51-90 Medium
91-130 High
>130 Very High
Test expansion index pertama kali dikembangkan di selatan California pada akhir tahun 1960 an,pada suatu masa dimana beberapa agensi lokal mengembangkan suatu metode testing yang
standar untuk daerahnya. Metode ini di evaluasi secara statistic pada lima laboratorium yang
berbeda di California, dan akhirnya diadopsi oleh Uniform Building Code (UBC Standard No 19-2)
dan banyak lembaga pemerintahan di California. Test ini sama dengan PVC test kecuali ekspansi
dilakukan pada suatu beban konstan tertentu.
EI = 100 h x F
Dimana :
h = percent swell
F = fraction passing No 4. sieve
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Engineering Index Properties
Laboratory and Field Data Probable Expansion(% Total Volume
Change)
Degre of Expansion
PercentagePassingNo 200Sieve
LiquidLimit(%)
StandardPenetratonResistance(Blows/ft)
>95 > 60 > 30 > 10 Very High
60 - 95 40 60 20 30 3 -10 High
30 60 30 40 10 20 1 5 Medium
< 30
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Engineering Index Properties
LL (%) PI (%) mnat, atsf ProbableSwell(%)
Potential SwellClassification
> 60 > 35 >4 < 1.5 High
50 60 25 35 1.5 4 0.5 1.5 Marginal
< 50 < 25 < 1.5 < 0.5 Low
50
Klasifikasi Tanah Ekspansif berdasarkan liquid limit,
index plastis dan insitu suction (Snethen, 1977
*mnat = soil suction pada natural moisture content
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COLE Classification Chart51
Klasifikasi mineralogy berdasarkan nilai activity dan cation-exchange activity
(CEC/percent clay )
a. (Pearring, 1963, Holtz , 1969)
b. Hamberg 1985
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COLE Classification Chart52
Nilai COLE sebagai fungsi dari % clay untuk
daerah pada chart Gambar 3.6
(Hamberg, 1985)
Ekspantion Potensial diindikasikan pada
diagram Ac verses CEAc (Hamberg,
1985)
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CASE STUDY :53
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CASE STUDY :55
Relation of suction compression index, Ch, to the slope of the soil water
characteristic curve (McKeen, 1992)
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CASE STUDY :56
Example of the relationship between soil suction and water content (McKeen, 1992)
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PREDIKSI HEAVE
TEORI VOLUME CHANGE PADA UNSATURATED SOIL
57
Typical ConsolidationCurve
(Curve 1 & 3)
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TEORI VOLUME CHANGE PADA
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TEORI VOLUME CHANGE PADA
UNSATURATED SOIL59
Idealized Soil Water
Characteristic Curve
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TEORI VOLUME CHANGE PADA
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TEORI VOLUME CHANGE PADA
UNSATURATED SOIL62
Shrinkage Test
Pressure Plate Test Consolidation Test
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TEORI VOLUME CHANGE PADA
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TEORI VOLUME CHANGE PADA
UNSATURATED SOIL64
)u(ulogC)u(logCe wamat
TEORI VOLUME CHANGE PADA
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TEORI VOLUME CHANGE PADA
UNSATURATED SOIL65
Fredlund : Postulate on developing constitutive surface
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TEORI VOLUME CHANGE PADA
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TEORI VOLUME CHANGE PADA
UNSATURATED SOIL
n
1i i0
i
e1
e.z
iatiwamin
1i i0
i ulogCuulogCe1.z
i
n
1i 0
wwn
1ii ze1
C
z
68
= total heavezi = ketebalan lapisan ke iei = (ef-e0)I
= Cmi log[ (ua-uw)f/(ua-uw)0]i
Cmi = matric suction indeks untuk lapisan iCti = efektif stress indeks untuk lapisan i = total stressua = tekanan udara poriuw = tekanan air pori
KESIMPULAN
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KESIMPULAN
1. Karakterisasi lapangan untuk tanah ekspansif, diawalidengan suatu survey pengenalan medan, pada survey iniharus diamati lokasi-lokasi yang menunjukkan terjadinyaswelling dan juga harus diamati factor-faktor yang dapatmengakibatkan perubahan volume pada tanah, misalnya
adanya kadar air pada lapisan permukaan tanah yangtinggi.
2. Karakterisasi lapangan dilanjutkan dengan suatuinvestigasi awal, dimana sampel yang diambil diuji
dengan suatu test indentifikasi potensi swelling.
KESIMPULAN
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KESIMPULAN
3. Investigasi yang detail dilakukan jika diketahui adanyapotensi swelling dengan pengambilan sampel kembaliuntuk diuji agar didapatkan presiksi besarnya heave.
4. Hasil prediksi besarnya heave yang akan terjadimenentukan alternative disain perbaikan tanahdilapangan selanjutnya.
5. Faktor-faktor skala mikro sangat mempengaruhi perilaku
ekspansif dari suatu jenis tanah, namun demikian factor-faktor skala mikro selama ini hanya dipakai sebagaipenentuan yang sifatnya kualitatif saja untuk memberikanpenjelasan terjadinya swelling pada tanah.
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Expansive Soil Case
E i S il
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Expansive Soils
Expansive Soils as fill material
Expansive Soils as foundation material
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S lli T t
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Swelling Test
STA 160+825 (4.00 - 4.50 m)
0
0.5
1
1.5
2
2.5
3
0 2000 4000 6000 8000 10000 12000 14000 16000
Time (minute)
Swelling(mm)
STA 160+825 (4.00 - 4.50 m)
0
0.5
1
1.5
2
2.5
3
1 10 100 1000 10000 100000
Time (minute)
Swelling(mm)
Swelling Potential
P t ti l S ll Cl ifi ti
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Potential Swell Classification
Technical Manual Foundation in Expansive Soils US ARMY Corp of
Engineering TM 5-818-7
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A ti Z
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Active Zone
Active Zone (Nelson and Miller,1991
Acti e Zone of E pansi e Soils
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Active Zone of Expansive Soils
Moisture content fluctuation on active zone of
expansive soil (Ning Lu and Likos, 2004)
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E i S il T M h d
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Expansive Soil Treatment Method
Moisture Density Relationship
Lime-Soil Mixture
Lime Mixed Treatment
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Lime Mixed Treatment
Most important points to consider for the successfulapplication of expansive soil treatment :
Usually 2-10% lime stabilizes reactive soil
Soil should be tested for lime reactivity and percentage of
lime needed
Calcareous and alkaline soils have good reactivity
Poorly drained soils have higher reactivities than well-drained
soils
Organics, sulfates and some iron compounds retards thepozzolanic reaction of lime
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Lime Mixed Treatment
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Lime Mixed Treatment
Variation in Compressive Strength as a
Function of Lime Content and Time
(Alaska Soil Stabilization DesignGuide,2002)
Effect of Lime on Optimum Moisture
Content and Density (Alaska Soil
Stabilization Design Guide,2002)
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E i S il T t t M th d
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Expansive Soil Treatment Method
Moisture barrier
Vertical and horizontal moisture barrier (US
Army TM 5-818-7)
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Expansive Soil Treatment Method
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Expansive Soil Treatment Method
MEMBRANE CUTOFF
Expansive Soil Construction Method
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: Post tensioning Slab
Expansive Soil Construction Method
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: Post tensioning Slab
Expansive Soil Construction Method
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: Post tensioning Slab
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