Kuat Geser Tanah Class 2

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<ul><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 1/47</p><p>Kuat Geser Tanah (Shear Strength)</p><p>- Triaxial Test-(Courtesy of COSC 323: Soils in Construction)</p><p>oleh:</p><p>A. Adhe Noor PSH, ST., MTStaf Pengajar Program Studi Teknik Sipil</p><p>Jurusan Teknik Fakultas Sains dan TeknikUniversitas Jenderal Soedirman</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 2/47</p><p>Triaxial Shear Test</p><p>Soil sample atfailure</p><p>Failure plane</p><p>Porousstone</p><p>impervious</p><p>membrane</p><p>Piston (to apply deviatoric stress)</p><p>O-ring</p><p>pedestal</p><p>Perspexcell</p><p>Cell pressure</p><p>Back pressure Pore pressure orvolume change</p><p>Water</p><p>Soilsample</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 3/47</p><p>Triaxial Shear Test</p><p>Specimen preparation (undisturbed sample)</p><p>Sampling tubes</p><p>Sample extruder</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 4/47</p><p>Triaxial Shear Test</p><p>Specimen preparation (undisturbed sample)</p><p>Edges of the sample arecarefully trimmed</p><p>Setting up the sample inthe triaxial cell</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 5/47</p><p>Triaxial Shear Test</p><p>Sample is covered with arubber membrane andsealed</p><p>Cell is completelyfilled with water</p><p>Specimen preparation (undisturbed sample)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 6/47</p><p>Triaxial Shear TestSpecimen preparation (undisturbed sample)</p><p>Proving ring tomeasure thedeviator load</p><p>Dial gauge to</p><p>measure verticaldisplacement</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 7/47</p><p>Types of Triaxial Tests</p><p>Is the drainage valve open?</p><p>yes no</p><p>Consolidatedsample</p><p>Unconsolidated</p><p>sample</p><p>Is the drainage valve open?</p><p>yes no</p><p>Drained</p><p>loading</p><p>Undrained</p><p>loading</p><p>Under all-around cell pressure c</p><p>cc</p><p>c</p><p>cStep 1</p><p>deviatoric stress( = q)</p><p>Shearing (loading)</p><p>Step 2</p><p>c c</p><p>c+ q</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 8/47</p><p>Types of Triaxial Tests</p><p>Is the drainage valve open?</p><p>yes no</p><p>Consolidatedsample</p><p>Unconsolidatedsample</p><p>Under all-around cell pressure c</p><p>Step 1</p><p>Is the drainage valve open?</p><p>yes no</p><p>Drainedloading</p><p>Undrainedloading</p><p>Shearing (loading)</p><p>Step 2</p><p>CD test</p><p>CU test</p><p>UU test</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 9/47</p><p>Consolidated- drained test (CD Test)</p><p>Step 1: At the end of consolidation</p><p>VC</p><p>hC</p><p>Total, = Neutral, u Effective, +</p><p>0</p><p>Step 2: During axial stress increase</p><p>VC =VC</p><p>hC =hC</p><p>VC + </p><p>hC 0</p><p>V =VC + = 1</p><p>h =hC = 3</p><p>Drainage</p><p>Drainage</p><p>Step 3: At failure</p><p>VC + f</p><p>hC 0</p><p>Vf =VC +f= 1f</p><p>hf =hC = 3fDrainage</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 10/47</p><p>Deviator stress (q or d) = 13</p><p>Consolidated- drained test (CD Test)</p><p>1 = VC + </p><p>3 = hC</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 11/47</p><p>Volumecha</p><p>ngeofthe</p><p>sample</p><p>Expansion</p><p>Compression</p><p>Time</p><p>Volume change of sample during consolidation</p><p>Consolidated- drained test (CD Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 12/47</p><p>Deviatorstress,</p><p>d</p><p>Axial strain</p><p>Dense sand or</p><p>OC clay</p><p>(d)f</p><p>Dense sand orOC clay</p><p>Loose sand or</p><p>NC clay</p><p>Volumechang</p><p>eof</p><p>thesample</p><p>Expansion</p><p>Com</p><p>pression</p><p>Axial strain</p><p>Stress-strain relationship during shearing</p><p>Consolidated- drained test (CD Test)</p><p>Loose sand orNC Clay(d)f</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 13/47</p><p>CD tests How to determine strength parameters c and f</p><p>Deviatorstres</p><p>s,</p><p>d</p><p>Axial strain</p><p>Shear</p><p>stress,t</p><p> or </p><p>fMohr Coulombfailure envelope</p><p>(d)fa</p><p>Confining stress = 3a(d)fb</p><p>Confining stress = 3b</p><p>(d)fc</p><p>Confining stress = 3c</p><p>3c 1c3a 1a</p><p>(d)fa</p><p>3b 1b</p><p>(d)fb</p><p>1 = 3 + (d)f</p><p>3</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 14/47</p><p>CD tests</p><p>Strength parameters c and f obtained from CD tests</p><p>Since u = 0 in CDtests, = </p><p>Therefore, c = c</p><p>and f = f</p><p>cd and fd are usedto denote them</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 15/47</p><p>CD tests Failure envelopes</p><p>Shearstress,t</p><p> or </p><p>fdMohr Coulombfailure envelope</p><p>3a 1a(d)fa</p><p>For sand and NC Clay, cd = 0</p><p>Therefore, one CD test would be sufficient to determine fd ofsand or NC clay</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 16/47</p><p>CD tests Failure envelopes</p><p>For OC Clay, cd 0</p><p>t</p><p> or </p><p>f</p><p>3 1(d)f</p><p>c</p><p>c</p><p>OC NC</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 17/47</p><p>Some practical applications of CD analysis forclays</p><p>t t = in situ drained shearstrength</p><p>Soft clay</p><p>1. Embankment constructed very slowly, in layers over a soft clay deposit</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 18/47</p><p>Some practical applications of CD analysis forclays</p><p>2. Earth dam with steady state seepage</p><p>t = drained shear strength ofclay core</p><p>t</p><p>Core</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 19/47</p><p>Some practical applications of CD analysis forclays</p><p>3. Excavation or natural slope in clay</p><p>t = In situ drained shear strength</p><p>t</p><p>Note: CD test simulates the long term condition in the field.Thus, cd and fd should be used to evaluate the longterm behavior of soils</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 20/47</p><p>Consolidated- Undrained test (CU Test)</p><p>Step 1: At the end of consolidation</p><p>VC</p><p>hC</p><p>Total, = Neutral, u Effective, +</p><p>0</p><p>Step 2: During axial stress increase</p><p>VC =VC</p><p>hC =hC</p><p>VC + </p><p>hC u</p><p>Drainage</p><p>Step 3: At failure</p><p>VC + f</p><p>hC</p><p>Nodrainage</p><p>No</p><p>drainage</p><p>uf</p><p>V =VC + u = 1</p><p>h =hC u= 3</p><p>Vf =VC +f uf = 1f</p><p>hf =hC uf = 3f</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 21/47</p><p>Volumecha</p><p>ngeofthe</p><p>sample</p><p>Expansion</p><p>Compression</p><p>Time</p><p>Volume change of sample during consolidation</p><p>Consolidated- Undrained test (CU Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 22/47</p><p>De</p><p>viatorstress,</p><p>d</p><p>Axial strain</p><p>Dense sand or</p><p>OC clay</p><p>(d)f</p><p>Dense sand orOC clay</p><p>Loose sand</p><p>/NC Clay</p><p>u</p><p>+</p><p>-</p><p>Axial strain</p><p>Stress-strain relationship during shearing</p><p>Consolidated- Undrained test (CU Test)</p><p>Loose sand orNC Clay(d)f</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 23/47</p><p>CU tests How to determine strength parameters c and f</p><p>Deviatorstress,</p><p>d</p><p>Axial strain</p><p>Shearstress,t</p><p> or </p><p>(d)fb</p><p>Confining stress = 3b</p><p>3b 1b3a 1a</p><p>(d)fa</p><p>fcuMohr Coulomb failureenvelope in terms oftotal stresses</p><p>ccu</p><p>1 = 3 + (d)f</p><p>3</p><p>Total stresses at failure</p><p>(d)fa</p><p>Confining stress = 3a</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 24/47</p><p>(d)fa</p><p>CU tests How to determine strength parameters c and f</p><p>S</p><p>hearstress,</p><p>t</p><p> or 3b 1b3a 1a</p><p>(d)fa</p><p>fcuMohr Coulomb failureenvelope in terms oftotal stresses</p><p>ccu 3b 1b3a 1a</p><p>Mohr Coulomb failureenvelope in terms ofeffective stresses</p><p>f</p><p>C ufa</p><p>ufb</p><p>1 = 3 + (d)f -uf</p><p>3= 3 -uf</p><p>Effective stresses at failure</p><p>uf</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 25/47</p><p>CU tests</p><p>Strength parameters c and f obtained from CD tests</p><p>Shear strengthparameters in terms oftotal stresses are ccu and</p><p>fcu</p><p>Shear strengthparameters in terms ofeffective stresses are cand f</p><p>c = cd and f = fd</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 26/47</p><p>CU tests Failure envelopes</p><p>For sand and NC Clay, ccu and c = 0</p><p>Therefore, one CU test would be sufficient to determine fcu</p><p>and f(= fd) of sand or NC clay</p><p>Shearstress,t</p><p> or </p><p>fcuMohr Coulomb failureenvelope in terms oftotal stresses</p><p>3a 1a</p><p>(d)fa</p><p>3a 1a</p><p>f</p><p>Mohr Coulomb failureenvelope in terms ofeffective stresses</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 27/47</p><p>Some practical applications of CU analysis forclays</p><p>t t = in situ undrainedshear strength</p><p>Soft clay</p><p>1. Embankment constructed rapidly over a soft clay deposit</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 28/47</p><p>Some practical applications of CU analysis forclays</p><p>2. Rapid drawdown behind an earth dam</p><p>t = Undrained shear strengthof clay core</p><p>Coret</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 29/47</p><p>Some practical applications of CU analysis forclays</p><p>3. Rapid construction of an embankment on a natural slope</p><p>Note: Total stress parameters from CU test (ccu and fcu) can be used for stabilityproblems where,</p><p>Soil have become fully consolidated and are at equilibrium with theexisting stress state; Then for some reason additional stresses areapplied quickly with no drainage occurring</p><p>t = In situ undrained shear strength</p><p>t</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 30/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Data analysis</p><p>C = 3</p><p>C = 3Nodrainage</p><p>Initial specimen condition</p><p>3 + d</p><p>3</p><p>Nodrainage</p><p>Specimen conditionduring shearing</p><p>Initial volume of the sample = A0 H0</p><p>Volume of the sample during shearing = A H</p><p>Since the test is conducted under undrained condition,</p><p>A H = A0 H0</p><p>A (H0H) = A0 H0</p><p>A (1</p><p>H/H0</p><p>) = A0</p><p>z</p><p>AA</p><p>1</p><p>0</p><p>U lid t d U d i d t t (UU T t)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 31/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Step 1: Immediately after sampling</p><p>0</p><p>0</p><p>= +</p><p>Step 2: After application of hydrostatic cell pressure</p><p>uc =B 3</p><p>C = 3</p><p>C = 3 uc</p><p>3 =3 - uc</p><p>3 =3 - uc</p><p>Nodrainage</p><p>Increase of pwp due toincrease of cell pressure</p><p>Increase of cell pressure</p><p>Skemptons pore water</p><p>pressure parameter, B</p><p>Note: If soil is fully saturated, then B = 1 (hence, uc</p><p>= 3</p><p>)</p><p>U lid t d U d i d t t (UU T t)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 32/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Step 3: During application of axial load</p><p>3 + d</p><p>3</p><p>Nodrainage</p><p>1 =3 +d- uc ud</p><p>3 =3 - uc ud</p><p>ud =ABd</p><p>uc ud</p><p>= +</p><p>Increase of pwp due to increase</p><p>of deviator stress</p><p>Increase of deviator stress</p><p>Skemptons pore water</p><p>pressure parameter, A</p><p>U lid t d U d i d t t (UU T t)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 33/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Combining steps 2 and 3,</p><p>uc =B 3 ud =ABd</p><p>u=uc + ud</p><p>Total pore water pressure increment at any stage, u</p><p>u=B [3 + Ad]Skemptons porewater pressureequation</p><p>u=B [3 + A(13]</p><p>Unconsolidated Undrained test (UU Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 34/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Step 1: Immediately after sampling</p><p>00</p><p>Total, = Neutral, u Effective, +</p><p>-ur</p><p>Step 2: After application of hydrostatic cell pressure</p><p>V0 =ur</p><p>h0 =ur</p><p>C</p><p>C-u</p><p>r</p><p>+ uc</p><p>= -ur</p><p>+ c(Sr = 100%;B = 1)</p><p>Step 3: During application of axial load</p><p>C + </p><p>C</p><p>No</p><p>drainage</p><p>Nodrainage</p><p>-ur + c u</p><p>VC =C +ur - C=ur</p><p>h =ur</p><p>Step 3: At failure</p><p>V =C + + ur - c u</p><p>h =C +ur - c u</p><p>hf =C +ur - c uf =</p><p>3f</p><p>Vf =C +f+ ur - c uf = 1f</p><p>-ur+ c uf</p><p>C</p><p>C + fNodrainage</p><p>Unconsolidated Undrained test (UU Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 35/47</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Total, = Neutral, u Effective, +Step 3: At failure</p><p>hf =C +ur - c uf =3f</p><p>Vf =C +f+ ur - c uf = 1f</p><p>-ur+ c ufC</p><p>C + fNodrainage</p><p>Mohr circle in terms of effective stresses do not depend on the cell pressure.</p><p>Therefore, we get only one Mohr circle in terms of effective stress for differentcell pressures</p><p>t</p><p>3</p><p>1f</p><p>Unconsolidated Undrained test (UU Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 36/47</p><p>3b</p><p>1b3a</p><p>1af</p><p>3</p><p>1</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Total, = Neutral, u Effective, +Step 3: At failure</p><p>hf =C +ur - c uf =3f</p><p>Vf =C +f+ ur - c uf = 1f</p><p>-ur+ c ufC</p><p>C + fNodrainage</p><p>t</p><p> or </p><p>Mohr circles in terms of total stresses</p><p>uaub</p><p>Failure envelope, fu = 0</p><p>cu</p><p>Unconsolidated Undrained test (UU Test)</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 37/47</p><p>3b 1b</p><p>Unconsolidated- Undrained test (UU Test)</p><p>Effect of degree of saturation on failure envelope</p><p>3a 1a3c 1c</p><p>t</p><p> or </p><p>S &lt; 100% S &gt; 100%</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 38/47</p><p>Some practical applications of UU analysis forclays</p><p>t t = in situ undrainedshear strength</p><p>Soft clay</p><p>1. Embankment constructed rapidly over a soft clay deposit</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 39/47</p><p>Some practical applications of UU analysis forclays</p><p>2. Large earth dam constructed rapidly with nochange in water content of soft clay</p><p>Core</p><p>t= Undrained shear strength</p><p>of clay core</p><p>t</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 40/47</p><p>Some practical applications of UU analysis forclays</p><p>3. Footing placed rapidly on clay deposit</p><p>t = In situ undrained shear strength</p><p>Note: UU test simulates the short term condition in the field.Thus, cu can be used to analyze the short term</p><p>behavior of soils </p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 41/47</p><p>Example</p><p> Given</p><p> Triaxial compression tests on three specimens of a soil samplewere performed. Each test was carried out until the specimenexperienced shear failure. The test data are tabulated as follows:</p><p> Required</p><p> The soils cohesion and angle of internal friction</p><p>Specimen</p><p>Number</p><p>Minor Principal Stress</p><p>(kips/ft2)</p><p>Deviator Stress at Failure</p><p>(kips/ft2)</p><p>1 1.44 5.76</p><p>2 2.88 6.85</p><p>3 4.32 7.50</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 42/47</p><p>Example</p><p>Specimen</p><p>Number</p><p>Minor PrincipalStress</p><p>(kips/ft2)</p><p>Deviator Stressat Failure</p><p>(kips/ft2)</p><p>Major Principal</p><p>Stress (kips/ft2</p><p>)</p><p>1 1.44 5.76 7.2</p><p>2 2.88 6.85 9.73</p><p>3 4.32 7.50 11.82</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 43/47</p><p>Example</p><p>0 2 4 6 8 10 12 14</p><p>2</p><p>4</p><p>6</p><p>8</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 44/47</p><p>Example</p><p>0 2 4 6 8 10 12 14</p><p>2</p><p>4</p><p>6</p><p>8</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 45/47</p><p>Example</p><p>0 2 4 6 8 10 12 14</p><p>2</p><p>4</p><p>6</p><p>8</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 46/47</p><p>Example</p><p>0 2 4 6 8 10 12 14</p><p>2</p><p>4</p><p>6</p><p>8</p><p>4</p><p>2</p><p>2</p><p>1</p><p>/9.0</p><p>26</p><p>4</p><p>2tan</p><p>4</p><p>2tan</p><p>ftkipc </p><p>f</p><p>f</p><p>f</p></li><li><p>8/2/2019 Kuat Geser Tanah Class 2</p><p> 47/47</p><p>THE END</p></li></ul>