SECOND EDITION
This edition first published 2016
© 2016 John Wiley & Sons, Ltd
First Edition published in 1991
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Library of Congress Cataloging‐in‐Publication Data
Names: Carter, Michael, author. | Bentley, Stephen P., author.
Title: Soil properties and their correlations / Michael Carter and Stephen P. Bentley, Cardiff University, UK.
Description: Second edition. | Chichester, West Sussex, United Kingdom : John Wiley & Sons, Inc., 2016. | Includes bibliographical references and index.
Identifiers: LCCN 2016013755 (print) | LCCN 2016014304 (ebook) | ISBN 9781119130871 (cloth) | ISBN 9781119130901 (pdf) | ISBN 9781119130895 (epub)
Subjects: LCSH: Soil mechanics.
Classification: LCC TA710 .B4285 2016 (print) | LCC TA710 (ebook) | DDC 624.1/5136–dc23
LC record available at http://lccn.loc.gov/2016013755
A catalogue record for this book is available from the British Library.
The aims of this book are to provide a summary and discussion of commonly used soil engineering properties and to give correlations of various engineering properties.
The book includes:
A consideration in describing the various properties has been an awareness by the authors that many geotechnical engineers and engineering geologists have little, if any, hands‐on experience of laboratory testing, and are often unaware of the procedures used to obtain the various soil properties and of the effects of poor or inappropriate practice.
The properties are also described in relation to their use in geotechnical analysis, in a way that we hope will give students and younger engineers an in‐depth appreciation of the appropriate use of each property and the pitfalls to avoid, and should also provide a useful reminder to more experienced professionals.
Many soil correlations were established in the early decades of soil mechanics, with there being no need to repeat the work once correlations had been established and verified by sufficient researchers. As a consequence, the correlations given in this book span a wide range of time, a few as far back as the 1930s, but we have also presented more recent work where this adds useful information. However, our intention in selecting correlations is to present those that will be of wide practical application, and the book is not intended as a research review. To aid their use in spreadsheet calculations, we have derived mathematical expressions to fit many of the correlations that were originally given only graphically. We have also tried to keep the work independent of national design codes, but it inevitably contains references to practices that are more prevalent in the English‐speaking world. Where references are made to classification systems and associated codes we have, where possible, included references to both UK and US practice.
We envisage and recommend that correlations be used in two ways: firstly, to obtain values of a property that has not been measured; and secondly, to provide additional values where some direct measurements of the property have been made. In the first case, where no values of a particular property have been directly measured, the values obtained from correlations should be viewed with caution and treated as preliminary, especially where the property value is critical to the predicted performance of a design. Where correlations are used in combination with direct measurements to provide supplementary values, the accuracy and reliability of the correlations can usually be verified, fine‐tuning the correlation if necessary, which may allow the values obtained by correlation to be viewed with more confidence.
While every care has been taken in the preparation of this book, with the very large amount of information that has been assembled it is possible that some errors have occurred; users should satisfy themselves that the information presented is correct. The authors can take no responsibility for consequences resulting from any errors in the book. The views expressed about the reliability and accuracy of correlations, typical values and other published information are based on the authors’ own experience and may not accord with those of other geotechnical specialists.
In creating a compendium of published correlations, we had to seek permission from many authors around the globe; for her role in this important and painstaking task, the authors would like to thank Carol Clark. Bringing together such a large number of disparate items of information from many sources also involved a great deal of checking, and our thanks go to ex‐colleagues Jason Williams and Max Lundie for their checking of some of the work, and especially to Mark Campbell who read through the entire script, noting errors and giving many helpful suggestions.
Symbol | Name of variable | Typical units (SI)* |
α | A scaling factor for estimating footing settlements from plate bearing test results. | D |
α | A factor for estimating values of coefficient of volume compressibility from static cone test results. | D |
α | Adhesion factor, for pile calculations. | D |
α | A factor used to estimate the pull‐out resistance of a soil reinforcement grid. | D |
Δp | A distance above or below the A‐line on a standard plasticity chart. | % |
θ | Angle of a plane, from the direction of maximum principle stress, on which stresses act. | Degrees |
μ | Viscosity of permeant for general seepage calculations. | kN.s/m2 |
ν | Poisson's ratio. | D |
π | Ratio of the circumference of a circle to its diameter (≈3.14159). | D |
ρ | Settlement. | m, mm |
σ | Direct stress. | kPa (kN/m2) |
σ' | Effective direct stress. | kPa (kN/m2) |
σ1, σ2, σ3 | Maximum, intermediate and minimum principal stresses. | kPa (kN/m2) |
σn | Effective earth pressure, used in soil nail calculations. | kPa (kN/m2) |
σv, σ'v | Vertical stress, or overburden pressure, in total and effective stress terms, respectively. | kPa (kN/m2) |
τ | Shear stress. | kPa (kN/m2) |
γ | Bulk density of soil. | kN/m3 |
γd | Dry density of soil. | kN/m3 |
γdmax | Maximum dry density, for relative density calculations. | kN/m3 |
γdmin | Minimum dry density, for relative density calculations. | kN/m3 |
γp | Density of permeant for general seepage equation. | kN/m4 |
γsub | Submerged density of soil. | kN/m3 |
γw | Density of water. | kN/m3 |
ϕ | Angle of shearing resistance (general, or in total stress terms). | Degrees |
ϕ' | Effective stress angle of shearing resistance. | Degrees |
ϕd | Drained angle of shearing resistance. | Degrees |
ϕr | Residual angle of shearing resistance (general). | Degrees |
a | Air voids content of soil. | % |
a | Component of influence factor Ic for estimating settlements of footings on sands. | D |
A | Area (nominal) of soil water flow. | m2 |
A | A correction factor for rod energy ratio in the standard penetration test. | D |
A | Percentage passing a 2.4 mm sieve, used in the calculation of suitability index. | % |
A | A constant used in the estimation of swelling potential from plasticity index. | D |
Ac | Activity value (of a clay). | D |
Ap | End area of penetration cone in a 1standard penetration test. | mm2 |
As | End area of penetration cone in a dynamic probe. | mm2 |
av | Coefficient of compressibility. (See also mv, coefficient of volume compressibility.) | m2/MN |
b | Component of influence factor Ic for estimating settlements of footings on sands. | D |
B | Footing width. | m |
B | A constant used in the estimation of swelling potential from plasticity index. | D |
c | Shape factor in general seepage calculations. | D |
c | Cohesion. | kPa (kN/m2) |
C | Percentage finer than 0.002 mm, used in the calculation of activity for a clay. | D |
c' | Effective stress cohesion. | kPa (kN/m2) |
C1 | Constant used in Hazen's formula to estimate the coefficient of permeability. | D |
CBR | California Bearing Ratio. | % |
Cc | Coefficient of curvature (coefficient of grading). | D |
Cc, Cr | Compression index, recompression index, respectively. | D |
cd | Drained cohesion. | kPa (kN/m2) |
CI | Consistency index. | % |
CN | Correction factor for overburden pressure, applied to SPT N‐values. | D |
cu | Undrained cohesion, shear strength. | kPa (kN/m2) |
Cu | Coefficient of uniformity. | D |
cv | Coefficient of consolidation. | cm2/s, m2/year |
Cα | Secondary compression index. | (log10 time)–1 |
Cαε , C' | Modified secondary compression index (sometimes referred to simply as the secondary compression index). | (log10 time)–1 |
d | Maximum length of drainage path in consolidation calculations. | m |
D | Depth of foundation (when calculating allowable bearing pressures on sands). | m |
D10 | The 10% particle size, also called the effective size. | mm (or μm) |
D30, D60 | The 30% and 60% particle sizes, respectively. | mm (or μm) |
Dn | The particle size at which n% of the material is finer. See also D10, D30, D60. | mm (or μm) |
Dr | Relative density (of granular soils). | D |
Ds | An effective particle size for permeability estimates, usually taken as D10. | mm |
e | Voids ratio. | D |
e | The natural number, approximately 2.718. | D |
E | Young's modulus (also called the elastic modulus). | kPa, MPa |
e1, e2 | Initial and final voids ratios in consolidation testing. | D |
Ed | Deformation modulus (also called the constrained modulus). | kPa, MPa |
emax | Maximum voids ratio, for relative density calculations. | D |
emin | Minimum voids ratio, for relative density calculations. | D |
ERr | Rod energy ratio in standard penetration test. | D |
F | The percentage passing the 75 μm sieve, used in the calculation of AASHTO classification group index. | % |
fl, fs, ft | Shape, layer thicknes and time factors, respectively, for estimating settlements of footings on sands. | D |
Fp | Drop distance of monkey (falling hammer) in a dynamic probe. | mm |
Fs | Drop distance of monkey (falling hammer) in a standard penetration test. | mm |
G | Shear modulus. | kPa, MPa |
Gs | Specific gravity of soil solids | D |
h | Thickness of specimen in consolidation testing. | mm |
H | Thickness of a compressible layer in consolidation testing. | m |
i | Hydraulic gradient in soil water flow. | D |
Ic | Influence factor for estimation of settlements of footings on sands. | D |
Ir | Rigidity index, used in rate‐of‐settlement estimates based on static piezocone test results. | D |
Ir | Swell index, used in the estimation of swelling pressure. | D |
k | Coefficient of permeability. | m/s, m/year |
K | A constant used in the estimation of swelling potential from plasticity index. | D |
K0 | Coefficient of earth pressure at rest. | D |
Kd | Depth factor for allowable bearing pressures on sands. | D |
Ks | Earth pressure coefficient use in driven pile calculations. | D |
L | Footing length. | m |
LI | Liquidity index. | % |
LL | Liquid limit. | % |
m | Moisture (water) content of soil. | % |
Mp | Mass of monkey (falling hammer) in a dynamic probe. | kg |
Ms | Mass of monkey (falling hammer) in a standard penetration test. | kg |
mv | Coefficient of volume compressibility. (See also av, coefficient of compressibility.) | m2/MN |
n | Porosity of soil. | D |
n | A factor used to estimate undrained shear strength from consistency index or liquidity index. | D |
N | SPT N‐value; blows of standard hammer to drive the SPT sampler or cone 300 mm. | Blows |
N1 | SPT N‐value corrected for overburden pressure. | Blows |
N1(60) | SPT N‐value corrected for overburden pressure and to a rod energy ratio of 60%. | Blows |
N60 | SPT N‐value corrected for rod energy ratio, ERr. (the “60” refers to standardisation to 60% rod energy.) | Blows |
Ncorrected | SPT N‐value corrected for silts and fine sands below the groundwater table. | Blows |
Nk | A factor used in the estimation of undrained shear strength from static cone tip resistance. | D |
O40, O80 | Pore diameters at which 40% and 80% of the pores are finer | mm, μm |
OCR | Overconsolidation ratio. | D |
p | Previous maximum overburden pressure, used in estimating settlements of footings on sands. | D |
p1, p2 | Initial and final pressures used in a stage of consolidation testing. | kPa (kN/m2) |
PI | Plasticity index. | % |
PL | Plastic limit. | % |
PM | Plasticity modulus. | % |
Pp | Penetration for each blow count in a dynamic probe. | mm |
Ps | Penetration for each blow count in a standard penetration test. | mm |
q | Quantity of flow of water through soil per unit time. | m3/s, m3/year |
q | Bearing pressure. | kPa (kN/m2) |
qa | Allowable bearing pressure. | MPa (MN/m2) |
qc | Measured cone resistance (pressure) in static cone tests. | kPa (kN/m2) |
qu | Ultimate bearing capacity. | kPa (kN/m2) |
R | Component of influence factor ft for estimating settlements of footings on sands. | D |
S | Degree of saturation. | % |
S | Swelling potential. | % |
s, su | Undrained shear strength. | kPa (kN/m2) |
St | Sensitivity | D |
SL | Shrinkage limit. | % |
t | Time, used in calculations or rates of consolidation and secondary compression. | s, years |
t1, t2 | Start and end times for secondary compression calculations. | s, years |
Tv | Basic time factor, used in calculations or rates of consolidation. | D |
u | Pore water pressure. | kPa (kN/m2) |
U | Degree of consolidation. | D |
v | Nominal velocity of flow of water through soil. | m/s, m/year |
vt | True velocity of flow of water through soil. | m/s, m/year |
WLW | Weighted liquid limit, used in the estimation of swelling potential. | % |
Ww | Weight of water (in the model soil sample). | g |
Y | Rate of frost heave. | mm/day |
* D = dimensionless; % values are also essentially dimensionless.