KUAT GESER TANAH
Created By : MARTINI ..KUAT GESER TANAH(SHEAR STRENGH OF
SOILEmbankmentStrip footingKERUNTUHAN GESER PADA TANAH(SHEAR
FAILURE OF SOILS)At failure, shear stress along the failure surface
(mobilized shear resistance) reaches the shear strength.Failure
surfaceMobilized shear resistanceRetaining wallKERUNTUHAN GESER
PADA TANAH (Shear failure of soils)Soils generally fail in
shearRetaining wallShear failure of soilsAt failure, shear stress
along the failure surface (mobilized shear resistance) reaches the
shear strength.Failure surfaceMobilized shear resistanceSoils
generally fail in shearMEKANISME KERUNTUHAN GESER(SHEAR
FAILUREMECHANISM)The soil grains slide over each other along the
failure surface.Bidang runtuh/geser
Shear failure mechanismAt failure, shear stress along the
failure surface () reaches the shear strength (f).Kuat geser tanah
adalah gaya perlawanan oleh butir-butir tanah akibat desakan atau
tarikan.Kuat geser () dan parameter kuat geser (kohesi, c dan sudut
gesek dalam, ) diperlukan dalam analisis :a. Daya dukung tanahb.
Stabilitas Lerengc. Tekanan tanah lateral pada dinding
penahan/turap
PENGERTIAN KUAT GESER TANAHMohr (1910), keruntuhan suatu bahan
terjadi akibat kombinasi tegangan normal dan tegangan geser.
Hubungan fungsi tegangan normal dan tegangan geser dinyatakan
dengan persamaan :
= tegangan normal = tegangan geser
PENGERTIAN KUAT GESER TANAHBila tanah mengalami pembebanan akan
ditahan oleh :a. Kohesi tanah, tergantung jenis tanah dan
kepadatannyab. gesekan antar butir-butir tanah yang besarnya
berbanding lurus dengan tegangan normal pada bidang
gesernya.PENGERTIAN KUAT GESER TANAHCoulomb (1776) mendefinisikan
kuat geser/tegangan geser :
Persamaan ini disebut kriteria keruntuhan atau kegagalan
Mohr-Coulomb, garis selubung kegagalan diperlihatkan pada gambar
berikut
PENGERTIAN KUAT GESER TANAHKriteria Keruntuhan Mohr-Coulomb
Parameter kuat geserDalam persamaan keruntuhan Mohr Coulomb ,
ada dua parameter kuat geser yang Sangat diperlukan yaitu :Kohesi
(cohesion), c Sudut Gesek Dalam (internal friction), Pengujian
Laboratorium dan lapangan untuk menentukan Parameter Kuat Geser
adalah1. Uji geser langsung (c dan f)2. Uji Triaksial (cu, c, fu
dan f)3. Uji Tekan Bebas (Unconfined), cu4. Uji Vane Shear,
cuPengujian Untuk Menentukan Parameter Kuat GeserUji GESER
LANGSUNGTanah pasir, lempung, lanau atau campuranSampel berbentuk
kotak atau lingkaranKondisi pengujian : tegangan efektif
(terdrainase) atau tegangan total (tak terdrainase)Kondisi tersebut
dicapai dengan mengatur kecepatan penggeseran
HASIL UJI GESER LANGSUNG
UJI TRIAKSIAL
Uji TRIAKSIALSampel tanah pasir, lanau dan lempungKondisi
pengujian :1. Unconsolidated Undrained (UU), paramater yang
diperoleh cu dan fu2. Consolidated Undrained (CU), parameter cu dan
fu 3. Consolidated Drained (CD), parameter c dan f Prinsip UJI
TRIAKSIAL
Hasil Uji TRIaksial
HASIL UJI TRIAKSIAL
HASIL UJI TRIAKSIAL
Uji KUAT TEKAN BEBAS (unconfined)
Unconfined Compression Test (UC Test)s1 = sVC + Ds s3 = 0
Confining pressure is zero in the UC testUnconfined Compression
Test (UC Test)s1 = sVC + Dsf s3 = 0 Shear stress, tNormal stress,
squNote: Theoritically qu = cu , However in the actual case qu <
cu due to premature failure of the sampleUJI VANE SHEAR
PLAN VIEWVane shear testThis is one of the most versatile and
widely used devices used for investigating undrained shear strength
(Cu) and sensitivity of soft claysBore hole (diameter = DB)h >
3DB)VaneDHApplied Torque, TVaneTRupture surfaceDisturbed soilRate
of rotation : 60 120 per minuteTest can be conducted at 0.5 m
vertical intervalsVane shear testSince the test is very fast,
Unconsolidated Undrained (UU) can be expected CuCuT = Ms + Me + Me
= Ms + 2Me Me Assuming a uniform distribution of shear strength
d/2d/2CuhVane shear testSince the test is very fast,
Unconsolidated Undrained (UU) can be expected CuCuMs Shaft shear
resistance along the circumference
T = Ms + Me + Me = Ms + 2Me Correction for the strength
parameters obtained from vane shear testBjerrum (1974) has shown
that as the plasticity of soils increases, Cu obtained by vane
shear tests may give unsafe results for foundation design.
Therefore, he proposed the following correction.Cu(design) =
lCu(vane shear) Where, l = correction factor = 1.7 0.54 log (PI)PI
= Plasticity IndexIn-situ shear tests Vane shear test Torvane
(suitable for very soft to stiff clays) Pocket Penetrometer
PressuremeterStatic Cone Penetrometer test (Push Cone Penetrometer
Test, PCPT) Standard Penetration Test, SPT
TorvaneTorvane is a modification to the vaneIn-situ shear tests
Vane shear test Torvane Pocket Penetrometer (suitable for very soft
to stiff clays) PressuremeterStatic Cone Penetrometer test (Push
Cone Penetrometer Test, PCPT) Standard Penetration Test, SPT
Pocket PenetrometerPushed directly into the soil. The unconfined
compression strength (qu) is measured by a calibrated
spring.Swedish Fall Cone (suitable for very soft to soft clays)The
test must be calibratedSoil sampleCu Mass of the cone
1/(penetration)2In-situ shear tests Vane shear test Torvane Pocket
Penetrometer Pressuremeter (suitable for all soil types)Static Cone
Penetrometer test (Push Cone Penetrometer Test, PCPT) Standard
Penetration Test, SPTPressuremeter
Pre bored or self bored holeGuard cellMeasuring cellGuard
cellCoaxial tubeWaterAirPressuremeterPre bored or self bored
holeGuard cellMeasuring cellGuard cellCoaxial
tubeWaterAirPressureVolumetric expansionTimePressureVolumetric
expansionPseudo- elastic phaseElastic phaseIn-situ shear tests Vane
shear test Torvane Pocket Penetrometer PressuremeterStatic Cone
Penetrometer test (Push Cone Penetrometer Test, PCPT) (suitable for
all soil types except very course granular materials) Standard
Penetration Test, SPTStatic Cone Penetrometer testCone
penetrometers with pore water pressure measurement capability are
known as piezocones40 mm40 mm40 mm40 mmStatic Cone Penetrometer
testForce required for the inner rod to push the tip (Fc) and the
total force required to push both the tip and the sleeve (Fc + Fs)
will be measuredPoint resistance (qc) = Fc/ area of the tipSleeve
resistance (qs) = Fs/ area of the sleeve in contact with
soilFriction Ratio (fr) = qs/ qc 100 (%)Various correlations have
been developed to determine soil strength parameters (c, f, ect)
from frIn-situ shear tests Vane shear test Torvane Pocket
Penetrometer PressuremeterStatic Cone Penetrometer test (Push Cone
Penetrometer Test, PCPT)Standard Penetration Test, SPT (suitable
for granular materials)Standard Penetration Test, SPTSPT is the
most widely used test procedure to determine the properties of
in-situ soils63.5 kg0.76 mDrill rod0.15 m0.15 m0.15 mNumber of
blows = N1Number of blows = N2Number of blows = N3Standard
penetration resistance (SPT N) = N2 + N3Number of blows for the
first 150 mm penetration is disregarded due to the disturbance
likely to exist at the bottom of the drill holeThe test can be
conducted at every 1m vertical intervalsVarious correlations have
been developed to determine soil strength parameters (c, f, ect)
from NKUAT GESER TANAH PASIR
KUAT GESER TANAH PASIR DAN LEMPUNG
Penggunaan Parameter hasiil uji triaksial untuk kondisi
pengujian UU (Unconsolidated Undrained)
Penggunaan Parameter hasiil uji triaksial untuk kondisi
pengujian CU (consolidated Undrained)
Penggunaan Parameter hasiil uji triaksial untuk kondisi
pengujian CD (consolidated drained)
HubunGan nilai c dan terhadap hasil uji sondir dan SPt
Parameter C dan Berdasarkan uji UU, CU dan Cd
Kuat GESER tanah berdasarkan jenis pengujian
UJI GESER LANGSUNG Untuk 2 material berbeda
Sudut gesek tanah dengan material bangunan
Sudut gesek tanah dan material
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