kuat-geser-tanah-direct-shear.ppt

Kuat Geser TanahDirect Shear Test (Uji Geser Langsung) Reza P. Munirwan, ST, M.Sc Determination of shear strength parameters of soils (c, orc’’ Percobaan Laboratorium menggunakan sampel tanah tidak terganggu (undisturbed sample) Percobaan lab yang umum, 1.Direct shear test 2.Triaxial shear test Percobaan laboratorium lainnya, Direct simple shear test, torsional ring shear test, plane strain triaxial test, laboratory vane shear test, laboratory fall cone test Percobaan Lapangan 1. 2. 3. 4. 5. 6. 7. Vane shear test Torvane Pocket penetrometer Fall cone Pressuremeter Static cone penetrometer Standard penetration test Percobaan Laboratorium Kondisi Lapangan Model sampel tanah z vc hc hc vc Sebelum konstruksi vc +  hc z hc vc +  Selama dan sesudah konstruksi vc +  Percobaan Laboratorium Simulasi kondisi lapangan di laboratorium 0 vc 0 0 0 Model sampel tanah dari lapangan l a i x a r T Di hc rect sh ea r hc vc hc t s te vc +  vc te  st  vc Step 1 Atur alat tes dan sampel sedemikian rupa untuk kondisi tegangan awal hc Step 2 Berikan tegangan seperti yang akan diberikan dilapangan . Direct shear test Skema alat percobaan direct shear . Direct shear test 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 Persiapan sampel pasir Porous plates Komponen dari shear box Persiapan sampel pasir . Direct shear test Persiapan sampel pasir Leveling the top surface of specimen Pressure plate Specimen preparation completed . Direct shear test Prosedur Percobaan P Steel ball Pressure plate Porous plates S Proving ring to measure shear force Step 1: Apply a vertical load to the specimen and wait for consolidation . Direct shear test Prosedur Percobaan P Steel ball Pressure plate Porous plates S Proving ring to measure shear force Step 1: Apply a vertical load to the specimen and wait for consolidation Step 2: Lower box is subjected to a horizontal displacement at a constant rate . Direct shear test Shear box Dial gauge to measure vertical displacement Proving ring to measure shear force Loading frame to apply vertical load Dial gauge to measure horizontal displacement . Direct shear test Analisis hasil percobaan Normal force (P)   Normal stress  Area of cross section of the sample Shear resistance developed at the sliding surface (S)   Shear stress  Area of cross section of the sample Note: Cross-sectional area of the sample changes with the horizontal displacement .  Dense sand/ OC clay f f Loose sand/ NC clay Expansion Compression Change in height of the sample Shear displacement Dense sand/OC Clay Shear displacement Loose sand/NC Clay .Direct shear tests pada pasir Stress-strain relationship Shear stress.  Normal stress =  3 . Normal stress =  2  f3  f2  f1 Normal stress =  1 Shear displacement Garis keruntuhan Mohr – Coulomb  Normal stress.Direct shear tests pada pasir Cara menentukan parameter kuat geser c dan  f  Shear stress at failure.  Shear stress. maka u = 0 Kesimpulan.Direct shear tests pada pasir Hal penting menggenai parameter kuat geser c and  pada pasir Pasir = tanah nonkohesi. maka c = 0 Percobaan Direct shear adalah drained dan tekanan air pori terdissipasi. ’ =  dan c’ = c = 0 . Direct shear tests pada lempung In case of clay. one test would take several days to finish) Failure envelopes for clay from drained direct shear tests Normally consolidated clay (c’ = 0) ’ Normal force. f  Overconsolidated clay (c’ ≠ 0) .  Shear stress at failure. horizontal displacement should be applied at a very slow rate to allow dissipation of pore water pressure (therefore. ca = adhesion. = angle of internal friction . it is required to determine the angle of internal friction between soil and the structural material (concrete.Interface tests on direct shear apparatus In many foundation design problems and retaining wall problems. steel or wood) P Soil S Foundation material  f  ca   ' tan  Where. karena ketebalan sampel percobaan yang kecil. Kekurangan percobaan direct shear  Arah bidang keruntuhan sudah diketahui. .Kelebihan percobaan direct shear  Drainase yang cepat dapat diperoleh.  Luas permukaan sliding berubah seiring dengan berjalannya proses percobaan.  Ketidak seragaman distribusi kuat geser sepanjang bidang runtuh.  Dapat digunakan untuk menggetahui parameter kuat geser pada pertemuan tanah. . Contoh Soal Hasil-hasil pengujian yang diperoleh dari pengujian geser langsung (direct shear) dengan ukuran sampel 60mm x 60mm pada tanah lempung berpasir sebagai berikut: Percobaan Beban Normal (kN) Beban Geser pada Keruntuhan (kN) 1 0. kegagalannya.20 0.80 0.40 0.26 3 0.205 2 0. Tentukan nilai dari .355 Gambar garis selubung parameter kuat gesernya. Penyelesaian Normal force (P)   Normal stress  Area of cross section of the sample Shear resistance developed at the sliding surface (S)   Shear stress  Area of cross section of the sample Percobaan Tegangan Normal (kN/m2) Tegangan Geser(kN/m2) 1 56 57 2 111 72 3 223 99 . k m f Penyelesaian k m       .       Shear stress at failure.Normal stress. PCPT)  Standard Penetration Test. SPT .In-situ shear tests  Vane shear test  Torvane  Pocket Penetrometer  Pressuremeter  Static Cone Penetrometer test (Push Cone Penetrometer Test. PCPT)  Standard Penetration Test. SPT .In-situ shear tests  Vane shear test (suitable for soft to stiff clays)  Torvane  Pocket Penetrometer  Pressuremeter  Static Cone Penetrometer test (Push Cone Penetrometer Test. 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 Applied Torque.5 m vertical intervals . T Bore hole (diameter = DB) Disturbed soil Rupture surface h > 3DB) T Vane Vane H PLAN VIEW Rate of rotation : 60 – 120 per minute D Test can be conducted at 0. SPT .In-situ shear tests  Vane shear test  Torvane (suitable for very soft to stiff clays)  Pocket Penetrometer  Pressuremeter  Static Cone Penetrometer test (Push Cone Penetrometer Test. PCPT)  Standard Penetration Test. Torvane Torvane is a modification to the vane . In-situ shear tests  Vane shear test  Torvane  Pocket Penetrometer (suitable for very soft to stiff clays)  Pressuremeter  Static Cone Penetrometer test (Push Cone Penetrometer Test. PCPT)  Standard Penetration Test. SPT . Pocket Penetrometer Pushed 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) Cu ∞ Mass of the cone ∞ 1/(penetration)2 Soil sample The test must be calibrated . In-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. SPT . Pressuremeter Air Coaxial tube Water Pre – bored or self – bored hole Guard cell Measuring cell Guard cell . PCPT) (suitable for all soil types except very course granular materials)  Standard Penetration Test.In-situ shear tests  Vane shear test  Torvane  Pocket Penetrometer  Pressuremeter  Static Cone Penetrometer test (Push Cone Penetrometer Test. SPT . Static Cone Penetrometer test 40 mm 40 mm 40 mm 40 mm Cone penetrometers with pore water pressure measurement capability are known as piezocones . 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) . m ect) vertical intervals strength parameters from N Drill rod 0.15 m 0.76 (c. SPT SPT is the most widely used test procedure to determine the properties of in-situ soils 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 63.15 m Number of blows = N1 Number of blows = N2 Number of blows = N3 Standard penetration resistance (SPT N) = N2 + N3 .Standard Penetration Test.15 m 0.5 kg Various correlations have been developed to determine soil The test can be conducted at every 1m 0. SPT SPT (Manual operation) .Standard Penetration Test.