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    Kuat Geser Tanah

    Reza P. Munirwan, ST, M.Sc

    Direct Shear Test(Uji Geser Langsung)

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    Percobaan laboratorium lainnya,

    Direct simple shear test, torsional

    ring shear test, plane strain triaxial

    test, laboratory vane shear test,

    laboratory fall cone test

    Determination of shear strength parameters of

    soils c, forc, f)

    Percobaan Laboratoriummenggunakan sampel

    tanah tidak terganggu

    (undisturbed sample)

    Percobaan Lapangan

    Percobaan lab yang umum,

    1.Direct shear test

    2.Triaxial shear test

    1. Vane shear test

    2. Torvane

    3. Pocket penetrometer

    4. Fall cone

    5. Pressuremeter6. Static cone penetrometer

    7. Standard penetration test

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    Percobaan Laboratorium

    Simulasi kondisi lapangan

    di laboratorium

    Step 1

    Atur alat tes dan

    sampel sedemikian

    rupa untuk kondisi

    tegangan awal

    svc

    svc

    shcshc

    Model sampeltanah dari

    lapangan

    0

    00

    0

    Step 2

    Berikan tegangan

    seperti yang akan

    diberikan dilapangan

    svc + Ds

    shcshc

    svc + Ds

    svc

    svc

    t

    t

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    Direct shear test

    Skema alat percobaan direct shear

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    Direct shear test

    Persiapan sampel pasir

    Komponen dari shear box Persiapan sampel pasir

    Porous

    plates

    Direct shear test adalah percobaan yang paling sesuai untuk

    kondisi percobaan consolidated drained khususnya pada tanah

    granular (contoh: pasir/sand) atau lempung keras/stiff clays

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    Direct shear test

    Leveling the top surface

    of specimen

    Persiapan sampel pasir

    Specimen preparation

    completed

    Pressure plate

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    Direct shear test

    Prosedur Percobaan

    Porous

    plates

    Pressure plate

    Steel ball

    Step 1: Apply a vertical load to the specimen and wait for consolidation

    P

    Proving ring

    to measure

    shear force

    S

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    Direct shear test

    Step 2: Lower box is subjected to a horizontal displacement at a constant rate

    Step 1: Apply a vertical load to the specimen and wait for consolidation

    PProsedur Percobaan

    Pressure plate

    Steel ball

    Proving ring

    to measure

    shear force

    S

    Porous

    plates

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    Direct shear test

    Analisis hasil percobaan

    sampletheofsectioncrossofArea

    (P)forceNormalstressNormal s

    sampletheofsectioncrossofArea

    (S)surfaceslidingat thedevelopedresistanceShearstressShear t

    Note: Cross-sectional area of the sample changes with the horizontaldisplacement

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    Direct shear tests pada pasir

    Shearstres

    s,t

    Shear displacement

    Dense sand/OC claytf

    Loose sand/

    NC clayf

    Dense sand/OC Clay

    Loose sand/NC ClayChangeinheight

    ofthesample Ex

    pansion

    Com

    pression Shear displacement

    Stress-strain relationship

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    tf1

    Normal stress = s1

    Direct shear tests pada pasir

    Cara menentukan parameter kuat geser c danf

    Shearstress,

    t

    Shear displacement

    tf2

    Normal stress = s2

    t

    f3

    Normal stress = s3

    S

    hearstressat

    failure,t

    f

    Normal stress, s

    f

    Garis keruntuhan MohrCoulomb

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    Direct shear tests pada pasir

    Hal penting menggenai parameter kuat geser c andf

    pada pasir

    Pasir = tanah non-kohesi,

    maka c = 0

    Percobaan Direct shearadalah drained dan

    tekanan air pori

    terdissipasi, maka u = 0

    Kesimpulan,

    f

    =f

    dan c= c =0

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    Kelebihan percobaan direct shear

    Drainase yang cepat dapat diperoleh, karena ketebalan sampel

    percobaan yang kecil.

    Dapat digunakan untuk menggetahui parameter kuat geser pada

    pertemuan tanah.

    Kekurangan percobaan direct shear

    Arah bidang keruntuhan sudah diketahui.

    Luas permukaan sliding berubah seiring dengan berjalannya

    proses percobaan.

    Ketidak seragaman distribusi kuat geser sepanjang bidang

    runtuh.

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    Hasil-hasil pengujian yang diperoleh dari pengujian geser langsung

    (direct shear) dengan ukuran sampel 60mm x 60mm pada tanah

    lempung berpasir sebagai berikut:

    Contoh Soal

    Percobaan Beban

    Normal (kN)

    Beban Geser pada

    Keruntuhan (kN)

    1 0.20 0.205

    2 0.40 0.26

    3 0.80 0.355

    Gambar garis selubung kegagalannya. Tentukan nilai dari

    parameter kuat gesernya.

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    Penyelesaian

    Percobaan Tegangan

    Normal (kN/m2)

    Tegangan

    Geser(kN/m2)

    1 56 572 111 72

    3 223 99

    sampletheofsectioncrossofArea

    (P)forceNormalstressNormal s

    sampletheofsectioncrossofArea

    (S)surfaceslidingat thedevelopedresistanceShearstressShear t

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    Penyelesaian

    Sh

    earstressatfa

    ilure,t

    f

    kN

    /

    m2

    Normal stress,s

    kN/

    m2)

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    In-situ shear tests

    Vane shear test

    Torvane

    Pocket Penetrometer

    Pressuremeter

    Static Cone Penetrometer test (PushCone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT

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    In-situ shear tests

    Vane shear test (suitable for soft to stiff clays)

    Torvane

    Pocket Penetrometer

    Pressuremeter

    Static Cone Penetrometer test (PushCone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT

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    PLAN VIEW

    Vane shear test

    This is one of the most versatile and widely used devices used for

    investigating undrained shear strength (Cu) and sensitivity of soft clays

    Bore hole

    (diameter = DB)

    h > 3DB)

    Vane

    D

    H

    AppliedTorque, T

    Vane T

    Rupture

    surfaceDisturbed

    soil

    Rate of rotation : 60120 per minute

    Test can be conducted at 0.5 m

    vertical intervals

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    In-situ shear tests

    Vane shear test

    Torvane (suitable for very soft to stiff clays)

    Pocket Penetrometer

    Pressuremeter

    Static Cone Penetrometer test (PushCone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT

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    In-situ shear tests

    Vane shear test

    Torvane

    Pocket Penetrometer (suitable for very soft to stiff clays)

    Pressuremeter

    Static Cone Penetrometer test (PushCone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT

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    Pocket Penetrometer

    Pushed directly into the soil. The unconfined compression

    strength (qu) is measured by a calibrated spring.

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    Swedish Fall Cone (suitable for very soft to soft clays)

    The test must be calibrated

    Soil sample

    CuMass of the cone1/(penetration)2

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    In-situ shear tests

    Vane shear test

    Torvane

    Pocket Penetrometer

    Pressuremeter (suitable for all soil types)

    Static Cone Penetrometer test (PushCone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT

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    Pressuremeter

    Prebored or

    selfbored hole

    Guard cell

    Measuring cell

    Guard cell

    Coaxial tube

    Water

    Air

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    In-situ shear tests

    Vane shear test

    Torvane

    Pocket Penetrometer

    Pressuremeter

    Static Cone Penetrometer test (Push

    Cone Penetrometer Test, PCPT)(suitable for all soil types except very course

    granular materials)

    Standard Penetration Test, SPT

    40

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    Static Cone

    Penetrometer

    test

    Cone penetrometers

    with pore water

    pressure measurement

    capability are known as

    piezocones

    40 mm

    40 mm

    40 mm

    40 mm

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    In-situ shear tests

    Vane shear test

    Torvane

    Pocket Penetrometer

    Pressuremeter

    Static Cone Penetrometer test (Push

    Cone Penetrometer Test, PCPT)

    Standard Penetration Test, SPT(suitable for granular materials)

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    Standard Penetration Test, SPT

    SPT is the most widely used test procedure to determine

    the properties of in-situ soils

    63.5 kg

    0.76 m

    Drill rod0.15 m

    0.15 m

    0.15 m

    Number of blows = N1

    Number of blows = N2Number of blows = N3

    Standard penetration resistance (SPT N) = N2+ N3

    Number of blows for the first 150 mm

    penetration is disregarded due to the

    disturbance likely to exist at the bottom

    of the drill hole

    The test can be conducted at every 1m

    vertical intervals

    Various correlations have been developed to determine soil

    strength parameters (c, f, ect) from N

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