Foundation Engineering About the Author Richard L Handy is a Distinguished Professor Emeritus in the Department of Civil, Construction and Environmental Engineering at Iowa State University A sought-after teacher, he served as the major professor for over 60 graduate students, many of whom have gone on to make major contributions in geotechnical engineering A large number of former students and associates recently collaborated to endow a Professorship in his name, and a book of collected papers was issued in his honor Dr Handy may be best known as the inventor of Borehole Shear Tests that perform in-situ measurements of cohesion and friction in soils and rocks The soil test was used in snow when he and six engineering students were conducting research on an epic voyage of a large ship in the ice-bound Northwest Passage They also observed the catenary shape of an igloo, which he later adapted to solve a problem that had intrigued Terzaghi, to mathematically define arching action in soils The analysis revealed that conventional analyses are on the unsafe side and explained a wall failure where there were four fatalities It received the Thomas A Middlebrooks Award of the American Society of Civil Engineers Dr Handy also was active in geology He proposed a variablewind hypothesis to explain the distribution of wind-blown silt (loess), and showed that the rate of growth of a river meander slows down in time according to a first-order rate equation He then applied the same equation to rates of primary and secondary consolidation in engineering In recognition of his contributions to geology he was elected a Fellow in the Geological Society of America and the American Association for the Advancement of Science Known for his sense of humor, Dr Handy liked to point out that it is better to have a joke that turns out to be an invention than an invention that turns out to be a joke His The Day the House Fell, published by the American Society of Civil Engineers, Reston, VA, for non-engineers, became a best-seller His book FORE and the Future ofPractically Everything published by Moonshine Cove Publishing, Abbeville, SC, adapts first-order rate equations to practically everything, including track world records and baseball home runs Dr Handy also founded and is the Past President of a company that bears his name The company manufactures and sells geotechnical instruments, with emphasis on in-situ test methods that were created and developed under his direction Foundation Engineering Geotechnical Principles and Practical Applications By Richard L Handy, Ph.D Distinguished Professor Emeritus Iowa State University New York Chkago San Francisco Athens London Madrid Mexico City Milan New Delhi Singapore Sydney Toronto Copyright© 2020 by McGraw-Hill Education All rights reserved Except as permitted under the United States Copyright Act of 1976, no part ofthis publication may be reproduced or distributed in any form or by any means, or stored in a database or 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McGRAW-HILL EDUCATION AND ITS LICENSORS MAKE NO GUARANTEES OR WARRANTIES AS TO THE ACCURACY, ADEQUACY OR COMPLETENESS OF OR RESULTS TO BE OBTAINED FROM USING THE WORK, INCLUDING ANY INFORMATION THAT CAN BE ACCESSED THROUGH THE WORK VIA HYPERLINK OR OTHERWISE, AND EXPRESSLY DISCLAIM ANY WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE McGraw-Hill Education and its licensors not warrant or guarantee that the functions contained in the work will meet your requirements or that its operation will be uninterrupted or error free Neither McGraw-Hill Education nor its licensors shall be liable to you or anyone else for any inaccuracy, error or omission, regardless of cause, in the work or for any damages resulting therefrom McGraw-Hill Education has no responsibility for the content of any information accessed through the work Under no circumstances shall McGraw-Hill Education and/or its licensors be liable for any indirect, incidental, special, punitive, consequential or similar damages that result from the use of or inability to use the work, even if any of them has been advised of the possibility of such damages This limitation of liability shall apply to any claim or cause whatsoever whether such claim or cause arises in contract, tort or otherwise Contents Preface xv Introduction xvii Defining What Is There 1.1 The Three Most Common Construction Materials 1.2 Two Classes of Foundations Support of Deep Foundations Expansive Clays Can Be Expensive Clays End Bearing on Rock Ground Improvement 1.3 Residual Soils Travel Is Wearing 1.4 Soil Layers Created by Weathering Topsoil "A Horizon" Subsoil "B Horizon" Shrinkage Cracks and Blocky Structure in Expansive Clays 1.5 Vertical Mixing in Expansive Clay 1.6 Influence from a Groundwater Table (or Tables) Groundwater Table and Soil Color A Perched Groundwater Table 1.7 Intermittent Recycling 1.8 Soil Types and Foundations Influence of a Groundwater Table Pull-up of Deep Foundations by Expansive Clay 1.9 Agricultural Soil Maps The Soil Series 1.10 Distinguishing between Alluvial Soils Rivers and Continental Glaciation Meanders and Cutoffs Oxbow Lake Clay Alluvial Fans Natural Levees Slack-Water (Backswamp) Floodplain Deposits Air Photo Interpretation 1.11 Wind-Deposited Soils Sand Dunes Eolian Silt Deposits 1.12 Landslides Landslide Scarps A No-No! Landslide Repair Method When Landslides Stop 1 2 2 3 4 5 6 6 7 9 9 10 10 11 12 12 12 12 13 13 13 14 14 15 16 y Yi Contents Recognizing Landslides Not a Good Place for a Patio Stopping a Landslide Drainage Structural Restraints: Piles, Stone Columns, and Retaining Walls Chemical Stabilization Drilled Quicklime Rock That Isn't There Near-Surface Features Shallow Caverns and Sinks Locating Underground Caverns Abandoned Mine Shafts and Tunnels Tunneling Machines and the Rock That Isn't There The Big Picture Mountain Ranges, Volcanoes, and Earthquakes Soil Responses to Earthquakes Earthquake Recurrence Intervals The Walkabout Problems Further Reading 17 17 17 18 18 19 20 20 20 21 21 21 22 23 23 24 Getting along with Classification • • • • 2.1 A Hands-On Experience 2.2 An Engineered Soil Moisture Content 2.3 Standardizing the Plastic Limit Test The Plastic Limit in Engineering 2.4 Going from Plastic and Remoldable to Liquid and Flowable Standardizing the LL Test The Fall Cone Test 2.5 The Plasticity Index 2.6 Atterberg Limits in Soil Classification 2.7 WWII and New Rules for Soil Classification 2.8 Atterberg Limits and Criteria for Expansion 2.9 Kinds of Clay Minerals A Layered Crystal Structure An Expansive Crystal Structure Going Tribal When Sodium, Na+, Replaces Calcium, Ca++ Drilling Mud 2.10 A Hands-On Test for Expansive Clay Field Test 2.11 Some Clues to Expansive Clay 2.12 Measuring Soil Particle Sizes Statistical Interpretation Defining Clay Size 25 25 25 26 26 27 27 27 28 29 30 31 31 31 32 34 34 34 34 34 34 35 35 36 1.13 1.14 1.15 1.16 16 16 16 16 Ca nt ent s 2.13 2.14 2.15 Particle Sizes Determined from Sedimentation Rates in Water Performing a Sedimentation Test Defining Clay Size Some Soil Characteristics Related to Grain Size Distribution Curves Defining Size Grades Gravel/Sand Sand/Silt Clay and Silt Expansive versus Non-expansive Clay Salt versus Fresh Water Clay Deposits Problems Further Reading Foundation Settlement 3.1 Castles and Cathedrals Cathedrals 3.2 A Scientific Approach to Foundation Settlement The Test A Eureka Moment! 3.3 Influence of Time 3.4 Amount of Settlement Void Ratio and Settlement Calculating a Void Ratio 3.5 Overconsolidation and the Compression Index 3.6 Consolidation Rate Defining a Drainage Distance 3.7 Pore Water Pressure and Foundation Bearing Capacity Field Monitoring 3.8 Pore Water Pressure Dissipation and Rate of Primary Consolidation 3.9 Evaluating Cv • • • • 3.10 A Reference Time for 90 Percent Primary Consolidation 3.11 It's Not Over Until It's Over: Secondary Consolidation 3.12 First-Order Rate Equations 3.13 Field Time for Secondary Consolidation Field Data 3.14 Defining a Preconsolidation Pressure Casagrande Method Correcting for Sample Disturbance Use and Misuse of OCR 3.15 Lambe's Stress Path Approach to Settlement 3.16 Differential Settlement Problems with Building Additions 3.17 The Other Shoe Problems 36 36 38 38 38 38 38 39 39 39 39 40 41 41 41 41 42 42 43 45 45 45 46 46 48 48 48 48 49 50 50 50 51 52 52 53 53 54 54 55 55 56 56 vii viii Contents References Further Reacting 57 57 Soils Behaving Badly 4.1 Expansive Clays Expansive Clay in a Consolidation Test 4.2 Two Classes of Expansive Clays Type G Clays Type P Clays How a Layer of Expansive Clay Can Cause Trouble Nature's Color Coding 4.3 Sorting Out Floodplain Clays What Makes River Floodplains Wide Braided Rivers Meandering Rivers A Shift from Braided to Meandering 4.4 Floodplain Soils of Meandering Rivers Oxbow Lake Clay Depth and Shape of an Oxbow Slack-Water or Backswamp Deposits 4.5 Deep Tropical Weathering and Expansive Clay 4.6 A Guide to Expansive Clay Crystal Structure in Control 4.7 Field Evidence for Expansive Clay More Bad Karma 4.8 Managing Expansive Clay The Chainsaw Method Structural Slabs, Grade Beams, and Piles Stripping off the Active Layer Observations of Strange Field Behavior 4.9 The Replacement Method How Does It Work? New Rule for Control of Expansive Clay Clues to Between-Layer Stacking of Water Molecules Hypothesis Why Does Clay Expansion Stop at Layers? What's in a Name? 4.10 Chemical Stabilization of Expansive Clay with Lime 4.11 Collapsible Soils Delayed Collapse Collapsible Alluvium 4.12 Regional Changes in Properties of Wind-Deposited Soils 4.13 Quick Clays! Vane Shear Does Not Just Measure Soil Cohesion 4.14 Liquefaction! Identifying Vulnerable Soils 59 59 59 60 60 60 60 60 61 61 61 61 61 62 62 62 62 63 63 63 64 64 65 65 65 65 67 67 67 68 68 69 69 69 69 70 70 71 71 72 72 73 73 www.freebookslides.com 64 Chapter Four MICA• ILLITE Nonexpansive SMECTITE Saturated F1auRE 4.2 A simplified illustration of clay mineral expansion: Mica has a layered structure but is not a clay mineral, as its sheets are held together by positively charged potassium ions Weathering can substitute calcium ions that allow limited expansion Black dots represent hydrogen atoms on water molecules Fleld Evidence for Expansive Clay Expansive clay exposed on dry lakebeds can show an obvious array of vertical tension cracks, and to preserve energy the cracks intersect in a honeycomb pattern A similar crack pattern exists in Arctic permafrost, created by thermal volume changes in frozen soil Tension cracking is less obvious when concealed under vegetation Clay subjected to repeated shrink-swell cycles can develop a "subangular blocky'' soil structure It occurs in a subsoil "B horizon" that typically is 1-2 m thick and follows ground surface contours The damaged clay has poor engineering qualities because individual blocks are preserved with thin films of clay, or "clay skins," that prevent bonding A subangular blocky structure can cause a clay soil to be misidentified as sand in cone penetration tests More Bad Karma Open tension cracks are an open invitation for debris and loose soil to fall in and prevent complete closing when clay between the cracks expands Repeated cycling causes lateral pressure to build up until it exceeds the unconfined compressive strength of the moist clay so it shears along inclined surfaces that become smeared with clay "slickensides" as shown in Fig 4.3 Such surfaces can severely affect engineering behavior, and shearing causes vertical mixing so topsoil and subsoil combine into a thick, black, clay www.freebookslides.com Solls BehHlng Badly layer The common name is black cotton soil; the scientific name is Vertisol, for vertical mixing Compaction in layers with tamping or sheepsfoot rollers can break up the shear planes, but the soil still is expansive F11uR! 4.3 Inclined shear surface preserwd by "slickensides• created by horizontal expansion pressures In expansive clay Shearing causes vertJcal mixing and permanently weakens the clay 4.8 Managing Expansive Clay 'The Chainsaw Method Damages from expansive clay may be postponed until trees are large enough for roots so suck appreciable amounts of water out of the soil An option follows a hard line and requires diplomacy, and will nothing to correct existing damages Structural Slabs, Grade Beams, and Plies Concrete floor slabs on expansive clays can be supported on a waffle-like arrangement of reinforced grade beams Grade beams supported on piers that extend down through the active layer often are framed and poured on top of crushable cardboard ''VerticeJ,/' and a substantial air gap must be provided between the floor and the soil Another procedure is to rei:nfott:e and integrate the beams with the floor, as shown in Fig 4.4 Stripping off the Active Layer The "active layer" of expansive clay undergoes seasonal shrink-swell cycles, so it might be assumed that removing the active layer might solve the expansive clay problem, but as shown in Fig 4.5, stripping it off but only sends the shrink-swell activity deeper where it remains destructive 65 www.freebookslides.com 66 Clllapter Four F11uR! 4.4 Construction of a structural floor with integrated grade beams on expansive clay After Brfeud et al (2016) Avallable onllne: ceprofs.tamu.edu/brlaud/lran 2010.pdf F1auH 4.1 Excavation tor the Malaprabha Left Bank Canal In expansive clay In lndla relocated the active clay layer downward, and the canal felled before It was opened (Inset) The entire canal was reconstructed using Katti's replacement method and has been in service for over 50 years (Image source: Author photo; inset image courtesy of the Central Boartl of Irrigation and Power, New Delhi.} www.freebookslides.com Solls Behning Badly A B c Dry density kg,lm3 Moisture content % Saturation% 1000 1400 rl'p \ 0.5 E £ 1.0 1800 T I } 10 20 30 40 50 30 50 70 90 110 ~ ~ "' ~ p