3.lecture geoteknik tgl sifat indeks tanah-wk3

GEOTEKNIK

I Gde Budi IndrawanEmail: [email protected]

Jurusan Teknik Geologi | Universitas Gadjah Mada

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III. SIFAT INDEKS TANAH

Jenis Tanah:a. Residual soil

Berada di atas batuan asal yang mengalami pelapukan.

Didominasi oleh pelapukan kimia.

b. Transported soil Telah mengalami transportasi

dan pengendapan.(Little, 1969)


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III. SIFAT INDEKS TANAH – Ukuran Butir

Metode: Dry sieving: ϕ > 0.075 mm Hydrometer: ϕ < 0.075 mm


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Dry sieve (butir berukuran > 0.075 mm)

Reddy (2002)

www.fhwa.gov


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Contoh analisa:

Reddy (2002)


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Hydrometer (butir berukuran < 0.075 mm)

Reddy (2002)


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Contoh analisa:

Reddy (2002)


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Reddy (2002)


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Reddy (2002)


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• Equivalent particle diameter (D):

• Corrected hydrometer reading (Rc):

• Percent finer (P):

• Adjusted percent fines (PA):

Reddy (2002)


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Distribusi ukuran butir (sieve + hydrometer)


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III. SIFAT INDEKS TANAH – Diagram Fase


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III. SIFAT INDEKS TANAH – Rasio Pori

Rasio Pori (void ratio), e

Vv = volume of voidVs = volume of solid

Das (1985)


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III. SIFAT INDEKS TANAH – Porositas

Porositas (porosity), n

Vv = volume of voidVt = total volume


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III. SIFAT INDEKS TANAH – Kandungan Air

Kandungan air (water content)1. Gravimetric water content, w

Expressed as a percentage Possible range: 0 - 500% (marine & organic soils) Metode:

o Air dry organic & residual soilso Oven dry (60 ºC) organic & residual soilso Oven dry (105 ºC)

2. Volumetric water content, qw

• Expressed as a decimal

Mw = mass of waterMs = mass of solid

Vw = volume of waterVt = total volume

ww

t

VV

q


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III. SIFAT INDEKS TANAH – Kandungan Air

Contoh:

Core 1 Container label 1,1 1,2 1,3Mcontainer (g) 15,87 14,38 14,81Mcontainer+wet sample (g) 55,67 46,87 57,45Mcontainer+oven dried sample (g) 51,12 43,15 52,31Mwater (g) 4,55 3,72 5,14Msolid (g) 35,25 28,77 37,50Water content (%) 12,91 12,93 13,71Average water content (%) 13,18


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III. SIFAT INDEKS TANAH – Tingkat Kejenuhan

Tingkat Kejenuhan (saturation degree), S

Percentage of void volume containing water Nilai:

o Fully saturated, S = 100%o Unsaturated, 0 < S < 100%o Dry, S = 0%

Vv = volume of void Vw = volume of water


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III. SIFAT INDEKS TANAH – Densitas

Densitas (density), r

Ms = mass of solidVs = volume of solid


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Mw = mass of waterVw = volume of water

Mt = Total massVt = Total volume


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III. SIFAT INDEKS TANAH – Specific Gravity

Relative Density, Dr

To indicate the in situ denseness or looseness of granular soil.

Expressed as a percentage.

Das (1985)

max

max minr

e eDe e

Where:emax = void ratio of the soil in the loosest stateemin = void ratio of the soil in the densest statee = in situ void ratio of the soil www.capco.co.uk

Sand vibrating table


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III. SIFAT INDEKS TANAH – Specific Gravity

Specific Gravity, Gs

Metode:oWater pycnometeroGas (helium) pycnometer

www.healthandcare.co.uk

www.gardco.com

Water pycnometer

Gas pycnometer


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III. SIFAT INDEKS TANAH – Contoh Perhitungan

Important relationship:

Contoh:

rt = rb = rd (1 + w) S e = w Gs


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III. SIFAT INDEKS TANAH – Contoh Perhitungan


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III. SIFAT INDEKS TANAH – Batas Konsistensi

Parameter paling penting yang mempengaruhi sifat keteknikan tanah: Tanah berbutir kasar (diameter > 75 µm): densitas Tanah berbutir halus (diameter < 75 µm): kandungan air


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III. SIFAT INDEKS TANAH – Konsistensi

Konsistensi tanah: Mudah tidaknya tanah mengalami deformasi/ perubahan

bentuk Tergantung pada ukuran butir dan kandungan air Diukur dengan “Atterberg limits”Atterberg limits:Tergantung pada kandungan airnya, tanah berbutir halus dapat berwujud:


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Pentingnya Atterberg limits:o Karakterisasi atau standarisasio Untuk memperkirakan prilaku tanah dari kandungan airnya (relatif terhadap Atterberg limits)

Contoh: Tanah dengan kandungan air mendekati PL akan mudah retak setelah dikompaksi


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o Liquid limit:

Reddy (2002)


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Contoh: Liquid Limit-Four Point Casagrande Test Mcontainer (g) 7,78 7,84 5,75 5,80 7,75Mcontainer+wet sample (g) 21,70 20,92 18,44 21,41 25,40Mcontainer+oven dried sample (g) 17,75 17,11 14,63 16,66 19,94Mwater (g) 3,95 3,81 3,81 4,75 5,46Msolid (g) 9,97 9,27 8,88 10,86 12,19Water content (%) 39,62 41,10 42,91 43,74 44,79Number of blows 40 33 25 20 17Liquid Limit (%) 42,9

0 10 20 30 40 5030

40

50

60

R² = 0.995202171880799

NO. BLOWS

WA

TER

CO

NTE

NT

(%)

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LL = 42,9%


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o Plastic limit:

Reddy (2002)


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Contoh:

Plastic Limit TestMcontainer (g) 16,89 17,39Mcontainer + wet sample (g) 30,02 30,41Mcontainer + oven dried sample (g) 27,50 27,98Mwater (g) 2,52 2,43Msolid (g) 10,61 10,59w (%) 23,75 22,95Plastic Limit (%) 23,35


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3.lecture geoteknik tgl sifat indeks tanah-wk3

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