Mechanics of Residual Soils

Residual soils are found in many parts of the world and are used extensively as construction materials for roads, embankments and dams, and to support the foundations of buildings, bridges and load-bearing pavements. The characteristics and engineering properties of residual soils can differ significantly from those of the more familiar transported soils. The fact that residual soils occur oftenin areas with tropical andsub-tropical climates and (extensively) in semi-arid climates, adds another dimension to their engineering performance, that of unsaturation. Although there are many books that deal with the mechanics of soils, these are based mainly on the characteristics and behaviour of saturated transported soils. The first edition of this book was the first book to be written specifically about the mechanics of residual soils. The book was prepared by a panel of authors drawn from the Technical Committee on Tropical and Residual Soils of the International Society for Soil Mechanics and Foundation Engineering. It was written as a practical professional guide for geotechnical engineers working with residual soils. The second edition has retained the valuable information contained in the first edition. The present editors and authors have extensively revised and augmented the content to bring it completely up to date, adding significantly to the sections on unsaturated soil mechanics andexpanding the range and number of instructive case histories. Furthermore, sections on pedocretes, dispersive soils and karst have been added.

Preface to second edition Acknowledgements Author biographies List of abbreviations and mathematical symbols 1 Origin and formation of residual soils G.E. Blight 1.1 Definitions relating to residual soils 1.2 Rock weathering processes 1.3 The effects of climate 1.4 The effects of topographic relief 1.5 General characteristics of residual soils 1.6 Depth and intensity of weathering 1.7 More about pedocretes 1.8 Transported soils that have weathered in situ 1.9 The weathering of soluble limestones and dolomites 1.10 Dispersive soils 1.11 Relict structures in residual soils that may affect their engineering performance 1.12 Rapidity of weathering 1.13 Detailed examination of a typical soil profile residual from an igneous rock 1.14 An introduction to the mechanics of unsaturated soils References 2 Microstructure, mineralogy and classification of residual soils A.B. Fourie,T.Y. Irfan, J.B. Queiroz de Carvalho, J.V. Simmons & L.D.Wesley 2.1 Microstructure and mineralogy related to weathering 2.2 Mineralogy and occurrence of weathering products 2.3 Determination of mineralogical composition 2.4 Microstructure of residual soils 2.5 Mineralogy and microstructure related to geotechnical properties 2.6 Examples of the mineralogy of a residual profile 2.7 Overcoming difficulties in measuring index parameters for residual soils 2.8 Classification of residual soils 2.9 Example of classification of a residual soil References 3 Describing the engineering properties of residual soils as observed in situ G.E. Blight & J.V. Simmons 3.1 Soil engineering survey 3.2 Soil engineering data 3.3 Detailed information on strength and permeability 3.4 Profile description 3.5 Simple in situ tests and soil sampling 3.6 Taking undisturbed soil samples for laboratory testing References 4 The mechanics of compaction and compacted residual soil G.E. Blight & J.V. Simmons 4.1 The compaction process 4.2 Consequences of unsatisfactory compaction 4.3 The mechanisms of compaction 4.4 Laboratory compaction 4.5 Precautions to be taken with laboratory compaction 4.6 Roller compaction in the field 4.7 Relationships between saturated permeability to water flow and optimum water content 4.8 Designing a compacted clay layer for permeability 4.9 Seepage through field-compacted layers 4.10 Control of compaction in the field 4.11 Special considerations for work in climates with large rates of evaporation 4.12 Additional points for consideration 4.13 Compaction of residual soils 4.14 The mechanics of unsaturated compacted soils during and after construction 4.15 Pore air pressures caused by undrained compression4.16 Summary References 5 Steady and unsteady flow of water and air through soils – permeability of saturated and unsaturated soils V.K. Garga & G.E. Blight 5.1 Darcy’s and Fick’s laws of steady state flow 5.2 Displacement of water from soil by air 5.3 Unsteady flow of air through partly saturated and dry soils 5.4 Unsteady flow of air through unsaturated soil 5.5 Measuring permeability to water flow in the laboratory 5.6 Observed differences between small scale and large scale permeability measurements 5.7 Laboratory tests for permeability to water flow 5.8 Measuring permeability to air flow 5.9 Methods for measuring water permeability in situ 5.10 Estimation of permeability from field tests 5.11 Large-scale permeability tests using a test pad 5.12 Permeability characteristics of residual soils References 6 Compressibility, settlement and heave of residual soils R.D. Barksdale & G.E. Blight 6.1 Compressibility of residual soils 6.2 The process of compression and swell in unsaturated soils 6.3 Biotic activity 6.4 Measuring the compressibility of residual soils 6.5 Settlement prediction calculations for raft and spread foundations 6.6 Settlement predictions for deep foundations 6.7 Movement of shallow foundations on residual soils 6.8 Collapse of residual soils References 7 Shear strength behaviour and the measurement of shear strength in residual soils R.P. Brenner, V.K. Garga & G.E. Blight 7.1 Behaviour and differences of residual soils from transported soils7.2 Laboratory strength testing 7.3 Field strength testing References 8 Case histories involving volume change and shear strength of residual soilsG.E. Blight 8.1 Settlement of two tower blocks on residual andesite lava 8.2 Settlement of an earth dam embankment constructed of residual soil 8.3 Settlement of an apartment block built on loess in Belgrade 8.4 Preheaving of expansive clay soils by flooding 8.5 Heave analysis for a profile of desiccated expansive clay at an experimental site8.6 The performance of tension piles subjected to uplift by expansive clays8.7 The mechanisms of piping failure along concrete outlet conduits 8.8 The stability of slopes of residual soil References Subject index Colour plates

Geoffrey Blight completed his PhD at Imperial College, London, on the mechanics of unsaturated soils, under the supervision of the legendary Alan Bishop. His early work, published jointly with Bishop in 1960, 1961 and 1963, provided data that is still being used by new generations of researchers on unsaturated soil behaviour. He soon became interested in residual soils, publishing his first work on unsaturated residual soils in 1963. He served as Chairman of the International Society for Soil Mechanics and Foundation Engineering’s Technical Committee on the Properties of Tropical and Residual Soils from 1994 to 1997 and edited and co-authored the book "Mechanics of Residual Soils", produced during his Chairmanship. Eng-Choon Leong is an Associate Professor at School of Civil Engineering, Nanyang Technological University, Singapore. He obtained his bachelors and masters degrees at the National University of Singapore and a PhD at the University of Western Australia. He has eighteen years of research and teaching experience in Geotechnical Engineering. His research interests are unsaturated soils, residual soils, soil dynamics, foundation engineering and numerical modeling. He has published widely in international journals and conferences. He has extensive experience in laboratory and field testing of saturated and unsaturated soils and in-situ monitoring of residual soil slopes. He has also developed a number of specialized laboratory testing apparatuses and data acquisition systems for field applications. He is also active in consultancy and national technical committees on standards. He has received several awards for his contribution to the accreditation of commercial soil testing laboratories and is a co-author of the ASTM Outstanding Article on the Practice of Geotechnical Engineering awarded in 2006.