CIV3247 Summary Notes Semester 2, 2020 Contents 1 Soil Consolidation 1 1.1 Sources and Causes of settlement . .1 1.2 Understanding Consolidation . .1 1.3 Oedometer Test Analysis . .3 1.4 Normally and Overconsolidated Clays . .4 1.5 Finding Preconsolidation Pressure and Over-Consolidation Ratio . .5 1.5.1 Casagrande Method . .5 1.5.2 Simplified Method . .6 1.5.3 Over-Consolidation Ratio . .7 1.6 Compression, Swelling indices and other parameters . .7 1.7 Calculation of Primary Consolidation Settlement . .8 1.7.1 NC Clays . .9 1.7.2 OC Clays . 10 1.8 Secondary Consolidation Settlement . 11 2 Time Rate of Consolidation 12 2.1 Terzaghi's Equation . 12 2.1.1 Derivation . 12 2.1.2 Analytical solution . 13 2.1.3 Maximum Drainage Path . 14 2.1.4 Average degree of consolidation . 14 2.1.5 Graphical Solution . 14 2.2 Average Degree of Consolidation . 15 2.3 Coefficient of Consolidation . 16 2.3.1 Logarithm of Time Method . 16 2.3.2 Square root of time method . 17 2.4 Primary consolidation settlment under a foundation . 18 3 Shear Strength of Soils and the Consolidated Drained Test 20 3.1 Soil Strength . 20 3.2 Mohr-Coulomb Failure Envelope . 20 3.3 Shear Strength Measurement: Triaxial Test . 21 3.4 Types of triaxial tests . 23 3.5 Consolidated-Drained (CD) Triaxial Test . 23 3.5.1 Stage 1: Saturation state . 24 3.5.2 Stage 2: Isotropic consolidation process . 24 3.5.3 Stage 3: Deviatoric Loading Phase . 25 3.5.4 Steps/notes for analysis . 26 3.6 Typical results from CD Tests . 26 3.7 Advantages/Disadvantages of the CD Test . 27 4 Consolidated Undrained and Unconsolidated Undrained Triaxial Tests 28 4.1 Consolidated-Undrained (CU) Triaxial Test . 28 4.1.1 Stage 1: Saturation state . 28 4.1.2 Stage 2: Isotropic consolidation . 28 4.1.3 Stage 3: Deviatoric loading phase . 28 4.2 Typical results obtained from the CU test . 29 4.2.1 Skempton's Pore Pressure at Failure . 30 4.3 Advantages/Disadvantages of the CU Test . 30 4.4 Unconsolidated Undrained (UU) Test . 31 i 4.4.1 Stage 1: Confining phase . 31 4.4.2 Stage 2: Deviatoric Loading Phase . 31 4.5 Typical results from the UU Test . 32 4.6 So many tests... which one to use??? . 32 5 Critical State Soil Mechanics 34 5.1 Stress Paths on the Shear Plane . 34 5.1.1 Cambridge Definition . 34 5.1.2 Stress path in isotropic loading . 35 5.1.3 Stress path for deviatoric loading . 35 5.1.4 Stress Paths in Triaxial Tests . 35 5.1.5 Critical State Line (CSL) . 36 5.2 The Volumetric Plane . 37 5.3 Drained Triaxial Tests in CSSM . 38 5.3.1 NC Clays and loose sands . 38 5.3.2 Heavily OC Clays and dense sands . 39 5.4 Undrained Triaxial Tests in CSSM . 40 5.4.1 NC Clays and loose sands . 40 5.4.2 Heavily OC Clays and dense sands . 41 5.5 Soil Yielding . 42 5.5.1 Yield surfaces (locus of yield points) . 43 5.5.2 Evolution/expansion of the yield surface . 43 5.6 State Boundary Surfaces (SBS) . 46 6 Modified Cam-Clay Model 47 6.1 Yield Surface Equation . 47 6.2 Elastic Strain . 48 6.2.1 Iteration . 49 6.3 Plastic Deformation . 50 6.3.1 Iteration . 51 6.3.2 But what does η mean?? . 52 6.4 Model Advantages and Limitations . 53 7 Slope Stability Analysis 54 7.1 Factor of Safety . 54 7.2 Stability of Infinite Slopes . 55 7.3 Factor of Safety with Seepage . 56 7.4 Limit Equilibrium Method . 57 7.5 Total Stress Analysis (Undrained stability of slopes) . 58 7.5.1 Determining the type of Slope Failure . 59 7.5.2 Toe circle failure . 60 7.5.3 Midpoint circle failure . 61 8 Slope Stability Analysis: Effective Stress Analysis 62 8.1 Fellenius Method . 63 8.2 Bishop's Simplified Method . 64 8.2.1 Iteration using Bishop's Method . 65 8.3 Solving problems with the Methods of Slices . 66 8.4 Limitations . 67 ii 9 Rock Slope Stability: Stereographic Analysis 68 9.1 Types of Rock Failure . 68 9.2 Some terms relating to discontinuities and planes . 69 9.2.1 Notation . ..