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SLOPE STABILITY ANDSTABILIZATIONMETHODSSecond Edition f

LEE W. ABRAMSO NHatch Mott MacDonaldMillburn,New JerseyTHOMAS S. LEEParsons, Brinckerhoff, Quade DouglasSan Francisco, CaliforniaSUNIL SHARMAUniversity of IdahoMoscow, IdahoGLENN M. BOYCEParsons, Brinckerhoff, Quade DouglasSan Francisco, California

A Wiley-lnterscience PublicationJOHN WILEY SONS , INC.

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CONTENTSPREFACE xviiACKNOWLEDGMENTS xixABO UT THE AUTHORS xxi

1 GENERAL SLOPE STABILITY CONCEPTS 1LeeW bramson1.1 Introduction / 11.2 Aim s of Slope Stability An alysis / 21.3 Natural Slopes / 21.4 Eng ineered Slopes / 3

1.4.1 Em bank ments and Fills / 31.4.2 Cut Slopes / 151.4.3 Landfills / 181.4.4 Re taining Structu res / 24

1.5 Lands lides / 251.5.1 Features and Dim ensions of Landslides / 251.5.2 Landslide Rates and Types of Movem ents / 29

1.6 Factors Contributing to Slope Failures / 331.7 Basic Concep ts Applied to Slope Stability / 341.8 Typical Input Data for Slope Stability Analyses / 36

1.8.1 Geologic Con ditions / 36

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Vi CONTENTS

1.8.2 Site Topography / 361.8.3 Possible Effects of Proposed Construc tion / 371.8.4 Material Prop erties / 391.8.5 Shear Streng th / 421.8.6 Grou ndw ater Conditions / 481.8.7 Seism icity / 49

1.9 Subsurface M odel and Back-An alysis for Slope StabilityAnalyses / 511.10 Conclusions / 53

References / 53

2 ENGINEERING GEOLOG Y PRINCIPLES 56ThomasS Lee2.1 Introduction / 562.2 Types and Charac teristics of Geo logic Soil Deposits / 56

2.2.1 Alluvial Dep osits / 572.2.2 Glacial Deposits / 652.2.3 Eolian Dep osits / 652.2.4 Residual Deposits / 672.2.5 Colluvial/Talus Dep osits / 692.2.6 M arine Dep osits / 702.2.7 M elanges / 712.2.8 Other Types of Dep osits / 72

2.3 Types and Characteristics of Rock s / 732.3.1 Shales / 742.3.2 Sandstones / 752.3.3 Limestones and Related Carbonate Rocks / 752.3.4 Igneous Rocks / 752.3.5 Pyrocrastic Volcanic Rocks / 762.3.6 M etamorphic Rocks / 76

2.4 Geologic Features Associated with Slopes / 762.4.1 Soil/Rock Fabric / 772.4.2 Geological Structures / 772.4.3 Discontinuities / 782.4.4 Groundwater / 782.4.5 Ground Stresses / 792.4.6 Weathering / 792.4.7 Preexisting Lan dslide Activities / 81

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CONTENTS VM

2.4.8 Clay M ineralogy / 822.4.9 Seismic Effects / 84

2.5 Landslides / 842.5.1 Landslide-Prone Occurrences / 852.5.2 Funda men tals of Landslides / 932.5.3 Useful Clues to Landslide Investigations andIdentifications / 95References / 99

GROUNDWATER CON DITIONS 102ThomasS Lee3.1 Introduc tion / 1023.2 Review of Groundw ater Fundam entals / 103

3.2.1 M ovement of Ground water / 1043.2.2 Principles of Groundw ater M echanics / 106

3.3 Site Co nditions / 1083.3.1 Groundwater Levels / 1083.3.2 Zon es / 1083.3.3 Aquifers / 1 1 13.3.4 Aq uicludes / 1123.3.5 Perched Water / 1123.3.6 Artesian Water / 1143.3.7 Springs / 114

3.4 Types of Grou ndw ater Flow / 1153.4.1 Runoff / 1153.4.2 Infiltration / 1173.4.3 Regional Flow / 118

3.5 Fluctuation of Groundwater Levels / 1213.5.1 Rainfa ll / 1213.5.2 Floo ds / 1233.5.3 Snow melt / 1243.5.4 Sudden Drawdown / 125

3.6 Influence of Geological Structures on Groundw aterFlows / 1253.7 Pore Pressures / 1273.7.1 Positive Pore Pressures / 1283.7.2 Nega tive Pore Pressures / 1313.7.3 M easurement of Pore Pressures / 133

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CONTENTS3.8 Water Levels for Design / 138

3.8.1 General / 1383.8.2 Wetting Band Approach / 139

3.9 Field Identification and Interpretation of Grou ndw aterConditions / 1423.9.1 Field Identification of Grou ndw ater Con ditions / 1423.9.2 Interpretation of Groundwater Conditions / 142

3.10 Groundw ater in Slope Stability Analysis / 1443 1 1 Developing a Groundw ater M odel from

the Field Da ta / 1443 1 2 Groundwater Effects on Slope Stability / 1463 1 3 Ground water in Rock / 150

3.11 M onitoring of Ground water Pressures / 1513 11 1 Piezom eters and Observation Wells / 1513 11 2 Installation of Piezom eters / 1573 11 3 Fluctuating Groundw ater Levels / 159

3.12 Othe r Instruments Rainfall Gages / 159References / 159

GEO LOG IC SITE EXPLORA TION 162ThomasS ee4.1 Introduction / 1624.2 Desk Study / 166

4.2.1 Available Existing Data / 1664.2.2 Previous Geo logic Exp lorations / 1724.2.3 Identification of Lan dslide-Prone Terrains through

Topographic Expressions / 1734.2.4 Air Pho tos / 175

4.3 Field Study / 1834.3.1 Site Reconn aissance / 183

4.4 Exploration M ethods / 1974.4.1 Introduction / 1974.4.2 Aug er Drilling / 1984.4.3 Rotary Wash Drilling / 2004.4.4 Limitations of Auger and Rotary Wash Drilling / 2034.4.5 Sampling in the Ground / 2034.4.6 Large Boreholes / 2044.4.7 Test Pits / 205

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CONTENTS iX

4.5 Testing M ethods / 2094.5.1 In Situ Testing / 2094.5.2 Geo physical Testing / 2234.5.3 Dow nhole Geophysics Logging / 2294.5.4 Mineralogy Tests / 2324.5.5 Radiocarbon Dating / 235

4.6 Exp loration Program Design / 2354.6.1 Locations and Num ber of Boreholes / 2354.6.2 Depth of Boreholes / 237References / 238

LABORATORY TESTING AND INTERPRETATION 242Sunil Sharma5.1 Introduction / 2425.2 Effective Stress Concep ts / 2435.3 Mohr Circle / 2445.4 M ohr-C oulo m b Failure Criterion / 245

5.4.1 M ohr-C oulom b Failure Envelope UnsaturatedSoils / 2475.4.2 M ohr-C oulom b Envelope inp-q Space / 249

5.5 Effective/Total Stress Analysis / 2505.5.1 Factors of Safety / 252

5.6 Stress Paths / 2545.6.1 Typical Field Stress Paths / 257

5.7 Shear Strength of Soils / 2595.7.1 Shear Strength of Granu lar Soils / 2605.7.2 Shear Strength of Fine-Grained Soils / 2605.7.3 Stres s-Stra in Characteristics of Soils / 2615.7.4 Discrepancies between Field and LaboratoryStrengths / 2635.7.5 Strength Testing / 2695.7.6 Selection and Preparation of Test Samples / 2715.7.7 Laboratory Test Conditions / 2725.7.8 The SHA NSE P Method / 2745.7.9 Triaxia l Tests / 2765 7 1 Direct Shear Test / 2835 7 11 Direct Simple Shear (DSS) Test / 2875 7 12 Unsaturated Tests / 288

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CONTENTS

5.8 Pore Pressure Parameters / 2915.8.1 Skem pton s Param eters / 2915.8.2 He nkel s Parameters / 291

5.9 Interpreta tions of Strength Tests / 2935.9.1 Triaxial Tests / 2935.9.2 Direct Shear Tests / 2985.9.3 Un saturated Tests / 3025.9.4 Selection of Design Shear Strengths / 302

5.10 Other Properties / 3055 1 1 Consolidation Tests / 3065 1 2 Permeab ility Tests / 3065 1 3 Com paction Tests / 3075 1 4 Classification Tests / 3085 1 5 Interpre tations of Classification Tests / 3105 1 6 Shrink/S well Potential / 3125 1 7 Slake Du rability / 3135 1 8 Co llapsibility / 3145 1 9 Dispersivity / 3155.10.10 Chem ical Tests / 3165.10.11 X-Ray Diffraction An alysis / 318

5.11 Quality Control/Quality Assurance / 319References / 321

SLOPE STABILITY CONC EPTS 329Sun/7 Sharma6.1 Introduction / 3296.2 Mo des of Failure / 3306.3 Fac tor of Safety Concep ts / 3326.4 Po re Water Pressures / 334

6.4.1 Phreatic Surface / 3356.4.2 Piezo me tric Surface / 3366.4.3 Exam ple / 3376.4.4 Neg ative Pore Pressures / 339

6.5 Block Analysis / 3396.5.1 Exam ple / 3416.6 Infinite Slope An alysis / 3436.6.1 Infinite Slopes in Dry Sand / 3436.6.2 Infinite Slope in c- Soil with Seepage / 344

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CONTENTS Xi

6.7 Planar Surface Analysis / 3456.7.1 Planar Surface Example / 348

6.8 Circular Surface An alysis / 3496.8.1 Circular Arc u =0) Method / 3496.8.2 4>u =0 Example / 3506.8.3 Friction Circle Method / 3506.8.4 Friction Circle Examp le / 352 y

6.9 M ethod of Slices / 3536.9.1 Ordinary M ethod of Slices (OM S) / 3586.9.2 Simplified Janbu M ethod / 3606.9.3 Simplified Bisho p Method / 3636.9.4 Generalized Limit Equilibrium (GLE) M ethod / 3646.9.5 Janb u s Generalized Procedure of Slices (GPS) / 3676.9.6 M ethod of SlicesA n Exam ple / 3706.9.7 Control of Negative Effective Stresses / 3756.9.8 Com parison of Limit Equilibrium M ethods / 376

6.10 Selection and Use of Limit Equilibrium Methods / 3786 1 1 Essential First Four-Steps / 3786 1 2 Selection of An alysis M ethod / 3796 1 3 Considerations for All Types of Analyses / 380

6.11 Design Charts / 3806 11 1 Historical Background / 3816 11 2 Stability Charts / 381

6.12 Seismic Analysis / 3936 12 1 Pseudostatic M ethod / 3946 12 2 New mark s Displacement Method / 3966 12 3 Accelerogram Selection for New ma rk sMethod / 3986 12 4 Com puted Permanent Displacements / 3996 12 5 Tolerable Perman ent Displacements / 408

6.13 Other Factors Affecting Slope Stability Ana lysis / 4096 13 1 Effect of Tension Cracks on Stability Analysis / 4096 13 2 Effects of Vegetation / 4106 13 3 Foundation Load s on Slopes / 411

6.14 Three-Dim ensional Ana lysis / 4126.15 Rock Slope Stability / 41 36.16 The Finite Element M ethod (FEM ) / 415

6 16 1 Exam ple of FEM Analysis of Slopes / 416

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XH CONTENTS

6.17 Com puter Analysis / 4196 17 1 Available Com puter Program s / 419

6.18 Probabilistic An alysis of Slopes / 42 06 18 1 Sources of Uncertainty / 4 206 18 2 Basic Probability Con cepts / 4216 18 3 Reliability Index / 4246 18 4 Probabilistic Formulation for Slopes / 4276 18 5 Probabilistic Analysis of Performance Function / 4276 18 6 Quantifying Uncertainty / 4366 18 7 Examples / 4386 18 8 Summary / 452References / 454

SLOPE STABILIZATION METH ODS 462LeeW bramson7.1 Introduc tion / 4627.2 Unload ing / 463

7.2.1 Excavation / 4637.2.2 Lightw eight Fill / 468

7.3 Buttressing / 4707.3.1 Soil and Rock Fill / 4747.3.2 Counterberms / 4747.3.3 Shear Keys / 4757.3.4 M echanically Stabilized Em bankm ents / 4777.3.5 Pneu sol (Tiresoil) / 480

7.4 Drainag e / 4827.4.1 Surface Drainag e / 4827.4.2 Subsurface Drainage / 483

7.5 Reinforcement / 4977.5.1 Soil Na iling / 4977.5.2 Stone Colum ns / 5077.5.3 Reticulated M icropiles / 5117.5.4 Geo synthetically Reinforced Slopes / 512

7.6 Retaining Walls / 5207.6.1 Gravity and Can tilever Retaining Walls / 5237.6.2 Driven Piles / 5237.6.3 Drilled Shaft Walls / 5247.6.4 Tieback Walls / 524

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CONTENTS Xiii7.7 Vegetation / 530

7.7.1 General Design Considerations / 5317.7.2 Vegetation Species / 5377.7.3 Erosion Control Mats and Blankets / 5387.7.4 Biotechnical Stabilization / 540

7.8 Surface Slope Protection / 541 ^7.8.1 General Design Considerations / 5427.8.2 Shotcrete / 5437.8.3 Chunam Plaster / 5447.8.4 M asonry / 5467.8.5 Rip-Rap / 546

7.9 Soil Hardening / 5477.9.1 Com pacted Soil-C em ent Fill / 5477.9.2 Electro-osmo sis / 5487.9.3 Thermal Treatment / 5497.9.4 Grouting / 5497.9.5 Lime Injection / 5507.9.6 Preconsolidation / 553

7.10 Rock Slope Stabilization M ethods / 5597 1 1 Removal of Unstable Rock / 5597 1 2 Catchment / 5627 1 3 Flattening of Slope / 5 657 1 4 Buttresses / 5657 1 5 Surface Protection / 5667 1 6 Reinforcement / 5687 1 7 Drainage / 5687 1 8 Use of Explosives / 5717 1 9 Rock Slope Stabilization Case

Histories / 5737.11 Alternatives to Slope Stabilization / 5 84

7 11 1 Com plete Removal of Slide Zone / 5857 11 2 Facility Reloca tion / 5857 11 3 Bridging / 587

7.12 Selection of Stabilization M ethods / 5877 12 1 Goals / 5887 12 2 Technical Constraints / 5887 12 3 Site Con straints / 5897 12 4 Environmental Constraints / 5907 12 5 Aesthetic Con straints / 590

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XiV CONTENTS

7 12 6 Schedule Constraints / 5907 12 7 Other Constraints / 5917 12 8 Cost / 591

7.13 Probable Cost An alysis of Stabilization Alternatives / 5917 13 1 Introduction / 5917 13 2 Dev eloping Alternative Schem es / 5927 13 3 Estimating Outcom es and Probabilities / 5927 13 4 Determ ining Probable Costs / 593References / 598

DESIGN,CONSTRUCTION, AND MAINTENANCE 604GlennM Boyce8.1 Introdu ction / 6048.2 Contract Do cum ents / 604

8.2.1 Contract Draw ings / 6058.2.2 Specifications / 6068.2.3 Geotechnical Design Reports / 606

8.3 Inspection during Construction / 6078.3.1 Inspection Gu idelines / 6078.3.2 Quality Control/Quality Assurance / 6088.3.3 Instrum entation / 6088.3.4 Instrumentation M onitoring / 627

8.4 Inspection following Construction / 6308.4.1 Introduc tion / 6308.4.2 Frequency of Inspections / 6318.4.3 Technical Inspe ctions / 6328.4.4 Engineering Inspections / 6328.4.5 Inspection Reports / 632

8.5 M aintenance / 6338.5.1 Access / 6338.5.2 Slope Performance Observations / 6338.5.3 Instrum ents / 6378.5.4 Drainage / 6378.5.5 Adjacen t U tilities / 638

8.6 Time Dom ain Reflectometry (TD R) / 6398.6.1 Introduction / 6398.6.2 M echanics of TDR / 639

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CONTENTS XV

8.6.3 Adv antages and Disadv antages of TDRover Inclinom eters / 640

References / 641

SHALLOW FAILURES 643Thomas S Lee9.1 Introduction / 6439.2 Seepage Flow M echan ism due to Infiltration / 6449.3 M echanism of Rainfall-Induced Landslides / 6459.4 Field Load ing Con ditions / 6479.5 Correlations between Land Slides and Rainfall / 648

9.5.1 Antecedent Rainfall / 6509.6 Rainfall Thresholds for Prediction of Shallow Failures / 6519.7 Types of Soils, Hyd rogeologic, and Geom orphologicFeatures / 652

9.7.1 Colluvium / 6529.7.2 Loess / 6539.7.3 Debris Flows / 6559.7.4 Residual Soils / 6569.7.5 Rapid Snow melt / 657

9.8 Effect of Perm eability of Surficial Stability / 6579.9 Standard Codes for Shallow Slope Stability / 6589.10 Design Practice for Shallow Slope Stability / 661

9 1 1 Debris Flow Hazard M itigation / 6629 1 2 Design of Loess Slopes / 6 63

9.11 Attending Landslide Incidents / 6649.12 Summ ary / 665References / 665

10 STABILITY OF LAND FILL SLOP ES 669LeeW bramson10.1 Un ique Na ture of Landfills / 66910.2 Typical Landfill Configurations / 66910.3 Landfill Waste Eng ineering Properties / 67510.4 Geosynthetics in Landfills and Eng ineering Properties / 679

10.4.1 Geom embranes / 68010.4.2 Geo textiles / 680

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10.4.3 Geon ets / 68010.4.4 Geogrids / 68210.4.5 Geo synthetic Clay Liners (GCL s) / 68410.4.6 Engineering Properties of Geo synthetics / 68510.4.7 Anchor Trenches / 686

10.5 Landfill Con struction / 68810.6 Slope Stability Con siderations / 692

10.6.1 Excavation Slope Stability / 69310.6.2 Waste Fill Stability / 69610.6.3 Cover System Stability / 700References / 702

INDEX 703