PRINCIPLES OF ENGINEERING GEOLOGY PRINCIPLES OF ENGINEERING GEOLOGY P B ATTEWELL and I W FARMER University of Durham LONDON CHAPMAN AND HALL A Halsted Press Book JOHN WILEY & SONS, INC., NEW YORK First published 1976 by Chapman and Hall Ltd 11 New Fetter Lane, London EC4P 4EE © 1976 J E Attewell and L C Attewell Sriftcover reprillt rifthe hardcover 1ft editiolt 1976 Typeset by Preface Ltd, Salisbury, Wilts Fletcher & Son Ltd, Norwich ISBN-13: 978-94-009-5709-1 e-ISBN-13: 978-94-009-5707-7 DOl: 10.1007/978-94-009-5707-7 All rights reserved No part of this book may be reprinted, or reproduced or utilized in any form or by any electronic, mechanical or other means, now known or hereafter invented, including photocopying and recording, or in any information storage and retrieval system, without permission in writing from the Publisher Distributed in the U.S.A by Halsted Press, a Division of John Wiley & Sons, Inc., New York Library of Congress Cataloging in Publication Data Attewell, P B Principles of engineering geology Engineering geology I Farmer, Ian William, joint author II Title TA705.A87 1975 624'151 75-20012 Contents Preface Symbols xi xvii 1.1 1.2 1.3 1.4 1.5 Composition of Rocks Origin and geological classification of rocks Rock forming minerals Clay minerals Base exchange and water adsorption in clay minerals Mineralogical identification 1 16 20 25 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 2.12 2.13 2.14 Rock Particles and Particle Systems Rock particle classification Typical rock particle systems Physical properties of particulate systems Permeability of particulate systems Representation of stress in a soil mass Effective stress Frictional properties of rock particles Soil deformation - drained granular media Soil strength - drained granular media Soil strength and deformation - clay soils Pore pressure parameters Rate of porewater pressure dissipation The critical state concept Limiting states of equilibrium 30 30 33 42 45 48 56 60 66 75 81 88 92 97 100 3.1 3.2 3.3 3.4 Clays and Clay Shales Interparticle attraction and repulsion Sediment formation and clay fabrics Unstable clay fabrics Glacial and periglacial clays 104 105 109 117 122 Contents vi 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 Depth - strength profiles Macrostructure of overconsolidated clays and clay shales Engineering influence of discontinuities in clay shales Classification of clay shales Consolidation and diagenetic considerations Physical breakdown of shales Suction pressure Swelling pressure Chemical and mineralogical analyses of clays Relationship between mineralogy, geochemistry and geotechnical properties of clays and clay shales 4.1 4.2 4.3 4.4 Rock as a Material Uniaxial strength Uniaxial short-term deformation Deformation mechanisms in rock Complete stress - strain characteristics of rock in uniaxial compression 4.5 Effect of rate and duration of loading 4.6 Deformation and failure of rocks in triaxial compression 4.7 Failure criteria for rocks 4.8 Yield criteria 4.9 Rock dynamics 4.10 Wave transmission through rocks 4.11 Wave attenuation 4.12 Rock as a construction material 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Preferred Orientation, Symmetry Concepts and Strength Anisotropy of some Rocks and Clays Studies of the orientation density distribution of clay minerals and other associated minerals X-ray texture goniometry Symmetry concepts Deformation paths Deformation ellipsoid Randomization Symmetry elements and sub-fabrics Crystallographic plane multiplicities and symmetry 125 130 143 146 150 153 157 162 167 175 182 184 194 199 206 210 218 224 229 232 234 239 244 250 251 252 260 263 263 266 271 272 Contents vii 5.9 Engineering influence of intrinsic anisotropy 285 5.10 Comparative degree of intrinsic anisotropy - mechanical 288 evidence from rock experimentation 5.11 Intrinsic strength anisotropy of brittle and semi-brittle 289 rocks comprising a dominant clay mineral control 5.12 Intrinsic anisotropy and sedimentation 300 5.13 Anisotropy of clay shales 302 5.14 Clay strength anisotropy 302 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 6.18 6.19 6.20 6.21 6.22 6.23 Rock Discontinuity Analysis The engineering interest in discontinuities Genesis and modification of fissures and slickensides Controls on fissuring and fissure patterns Classification of discontinuities Character of discontinuities Test specimen size-strength relationships Stereographic representation of discontinuity data Direct and inverse transformations from polar to equatorial angles Linear orthogonal transformations Eulerian angles Discontinuity survey techniques Analysis of discontinuity data Influence of gouge material and surface roughness characteristics of discontinuities Distributions Orientation density distribution of discontinuities Discontinuity shear stability in a poly axial stress field Shear strain energy concepts Preliminary consideration of certain types of discontinuity structure in two dimensions Statistics of scanlines through discontinuity distributions Continuity Preliminary shear stability analysis of discontinuities at the foundation interface of an earth or rock-fill dam Stability of jointed rock in the foundation of an arch dam Stability of a discontinuous clay surrounding an unlined tunnel 315 315 317 319 320 326 326 328 329 333 336 336 344 352 355 364 369 376 385 388 394 398 409 426 viii Contents 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 7.10 7.11 7.12 7.13 7.14 7.15 7.16 7.17 Site Investigation Preliminary investigation Aerial photographs Terrain evaluation for highway projects Geophysical exploration techniques Seismic refraction surveying Site exploration Borehole logging Sampling and testing Site investigation reports Mechanical tests in situ Field monitoring techniques Use of field seismic techniques in engineering geology Analysis of ground vibrations Marine geotechnical exploration Mining subsidence Probability theory in site investigation What is 'safety' in soil and rock mechanics? 427 429 437 442 448 453 457 465 475 483 484 503 512 514 529 534 547 557 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14 Groundwater Types of subsurface water Groundwater flow Seepage forces Drainage and drain wells Permeability tests - rock Permeability tests - soils Economic exploitation of groundwater Ownership of groundwater and permitted abstractions Groundwater exploration Regional investigations Simulation of groundwater regimes Well losses Improving aquifer yield Groundwater quality 560 560 565 577 580 585 591 598 601 601 614 618 626 627 627 9.1 9.2 9.3 Stability of Soil Slopes Planar slides Circular failure surfaces Slope stability case histories 632 633 635 645 Contents 9.4 9.5 9.6 9.7 9.8 9.9 9.10 9.11 Simple wedge method of analysis Use of design curves Pore pressure ratio Oay slopes and shear strength parameters Slope angle measurements in clays and clay shales Classification of gravitational mass movements in clay Rock breakdown and landform development Geomorphological classification of slope profile development 9.12 General methods of preventing slope failure 9.13 Highway slopes 9.14 Protection against coastal erosion 10 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 10.13 Rock Slope Stability Geomorphological classification of rock slope instabilities Classification of rock masses Character of joints in rock masses Engineering recognition of rock failure modes Surface roughness of joints Discontinuity roughness classification Planar sliding and the friction cone concept Instability on intersecting joint planes Influence of discontinuity orientation distributions Seismic influences on stability with respect to sliding Instability caused by block overturning General rock slope design curves Slopes in highway cuttings and embankments Ground Improvement 11.1 Shallow compaction 11.2 Deep compaction 11.3 Pre-loading and consolidation 11.4 Sand drains ll.5 Grout treatment 11.6 Fissure grouting 11.7 Hydrofracture ll.8 Cavity grouting 11.9 Electro-chemical stabilisation 11.10 Groundwater freezing II ix 661 672 674 675 683 688 697 704 705 708 714 720 720 730 738 743 749 753 758 765 787 792 797 803 809 814 817 821 826 830 836 851 855 863 866 871 x Contents 11.11 Bentonite suspension 1l.12 Ground anchors 874 879 Water Resources, Reservoirs and Dams Water requirements in England and Wales Planning of water resources Conjunctive use schemes Flood and dam design parameters Channel protection Design capacity of a storage reservoir Air-photo interpretation for catchment development Geological influences upon the selection of reservoir sites Foundation investigations Water movement into and out of a reservoir Synthetic flow generation techniques Dam foundations Classification of dam types according to their purpose, construction and foundation geology 12.14 Long term stability of earth dams 12.15 Dam seismicity 887 888 889 895 897 900 904 907 908 911 914 917 918 12 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.10 12.11 12.12 12.13 References 922 944 945 969 Supplementary References 1022 Author Index 1025 Subject Index 1035 Preface 'Engineering geology' is one of those terms that invite definition The American Geological Institute, for example, has expanded the term to mean 'the application of the geological sciences to engineering practice for the purpose of assuring that the geological factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for' It has also been defined by W R Judd in the McGraw-Hill Encyclopaedia of Science and Technology as 'the application of education and experience in geology and other geosciences to solve geological problems posed by civil engineering structures' Judd goes on to specify those branches of the geological or geo-sciences as surface (or surficial) geology, structural/fabric geology, geohydrology, geophysics, soil and rock mechanics Soil mechanics is firmly included as a geological science in spite of the perhaps rather unfortunate trends over the years (now happily being reversed) towards purely mechanistic analyses which may well provide acceptable solutions for only the simplest geology Many subjects evolve through their subject areas from an interdisciplinary background and it is just such instances that pose the greatest difficulties of definition Since the form of educational development experienced by the practitioners of the subject ultimately bears quite strongly upon the corporate concept of the term 'engineering geology', it is useful briefly to consider that educational background Engineering geologists have usually received a basic training in either a geological or engineering discipline and there seems to be a popular acceptance of the potential advantages and disadvantages of both forms of training Klaus John (1974) has summarized quite admirably the general feeling: 'They (geologists) prefer to approach a problem intuitively, indirectly, and in general qualitative terms, often preferring the problem to the results Complexities are emphasized, 300 Principles of Engineering Geology ,., 50 'Q '" 50 '$2 C\;x 40 300(\I (\Ix 40 ~ 30 'E '.f ~ 30 's ~ bM , 20 0" t$- 20 z 200 ::E tr • I (3 =30° 10 o o I o J .J ' - - I -L L L L L .J 10 a; Ibf in-2 xlO'3 I 20 0"3 I I 40 60 MN m,2 100 ~ ' I 80 10 0"3'bf in-2 X 10-3 I 20 I I 40 60 0"3 I 80 MN m-2 50 300 10 10 o 0"3 I I 20 Ibf in'2 x 10'3 I a; 910 40 MN m-2 I 60 I ' - - I -L L L L L-~~O 45678910 "3 Ibf in-2 x 10'3 I 80 I 20 0"3 I I 40 60 MN m-2 I 80 Figure 5.29 Theoretical and experimental principal stress relationships for Penrhyn slate Continuous line represents theoretical fit with B = 8.2 and I1c = 0.5 Circles are experimental data points at failure From Attewell and Sandford (l974c) For further reading on the anisotropic behaviour of schistose and other rocks, reference may be made to Deklotz and Stemler (1966), Mendes (1966} Akai et al (1970), Pinto (1970), and Rodrigues (1970) The anisotropic response of coal has been studied by Pomeroy et al (1970) 5.12 Intrinsic anisotropy and sedimentation Earlier in Chapter we have considered the influences imposed on clay mineral sedimentation characteristics by the electrolytic content Preferred Orientation, Symmetry and Strength Anisotropy 301 of the water through which they settle The preferred orientation of these minerals is also conditioned by the nature of the more equant minerals that sediment out with them Without delving further into this specialist subject, it will be appreciated that in a rock comprising closely-cyclic sedimentary structures, such as a laminated or varved mudstone, the degree of preferred orientation of the morphologically SILTY LAM INATED MUDSTONE Variation in anisotropic index and m ineralogy with depth into sample Anisotropic index Amount / 30 40 50 60 Depth No I LLI TE 0- 01 KAOLINITE \ 05 06 1'5- 07' f> I 2·0Q9 t 10 t., I I I • I I x i :\ 2,5- 3'0 - •I V ,~ ~\ 11 14 , I ,A.l.lll ite I A.I.Kaolinite ~~ } ~, \ I 08 \ o , I \ ,~/ ~"" 13 \ o 03 Illite ,0'oKaolinite tropic index I ·6 ~ O{o ~A nlSO' 0'5- RATIO I o Anisotropic I 12 ~Amount / 02 0·4 ·2 ~- ' p b o / , / • x ~ -"""""x Figure 5.30 Variation of degree of anisotropy through the laminations in a sample of Coal Measures mudstone (after Cripps, 1970) 302 Principles of Engineering Geology inequant minerals will tend to vary vertically through these structures This problem has been studied by Cripps (1970) using X-ray texture-goniometric methods and the results discussed by him in a sedimentological context Figure 5.30 is a plot of a number of parameters related to clay minerals and their preferred orientation against vertical distance through the laminations in a mudstone A cyclic variation with distance will be noted, and although it is somewhat irregular the general wavelength of the variation (~ 1.5 mm) coincides with the average lamination thickness The illite percentage in the general sample is about five times that of kaolinite, each of these minerals rising and falling in phase through the laminations It will be noted, however, that the anisotropic index values for the illite and kaolinite, that is, the degree of preferred orientation projected by their respective basal planes, have a tendency to vary half a wavelength out of phase, with the kaolinite being about three times as strongly preferred as the illite This latter can probably be attributed to a size effect, kaolinite crystals being much larger than those of illite 5.13 Anisotropy of clay shales From the earlier evidence of strength anisotropy in mudstone, a similar response is to be expected from a more fissile shale Wright and Duncan (1969) performed unconsolidated-undrained compression tests on specimens of Bearpaw shale and Pepper shale cut at various angles to the fissility Figure 5.31 shows that although there are considerable variations in absolute strength between the two shales, the form of the anisotropy is similar in both Maximum strength is mobilized when the compression is applied parallel to the 'horizontal fissuring' Directional strength differences are less clearly defined at low confining pressures in the Green River shale (Figure 5.32) but this material again demonstrates the manner in which the friction angle varies with specim en orientation 5.14 Clay strength anisotropy It will be apparent, from the discussion on clay fabrics in Chapter and from Rowe's (1972) Rankine lecture, that the swelling, consolidation and shear behaviour of a clay in particular, and its engineering behaviour in general, will be to some extent directiondependent We might expect, for example, that a flocculated clay in Preferred Orientation, Symmetry and Strength Anisotropy I 0,140 x £120 , , ~100 \ \ ~ U \ \ \ , \ ~ 40 ~ 20 00 914 \ \ ,, - /-" - C\I I E z ~ ~12 , OJ 10 ~c , -2 , e t - -80 ~1111"'" '0 - t -0 > 90° 0-75 t 0° f''.I':~ 0-70 0-65 t - 60 ~ ~ L -~ -L ~ ~L-~ -' 0-2 -5 1-0 2-0 4·0 -0 16-0 Effective stress ( log scole) kg! cm-2 (xl0 kN m -2 ) Figure 5.37 Consolidation curves for laminated clay tested at five different orientations (after Leach, 1973)_ clays from different areas tend to respond both absolutely and anisotropically in a different geotechnical manner Derived from consolidation tests and the recording of stress-strain relationships, the curve in Figure 5.36 indicates that at low normal effective stresses quite large strains result from direct closure of the laminations whereas the material is much stiffer when the compression takes place parallel to the laminations However, at higher normal effective stresses, with the stress-strain curves always concave-upwards, the sti ffness anisotropy disappears Displaying a similar effect, the void ratio is plotted in Figure 5.37 against the normal effective stress for different attitudes of the laminations with respect to the direction of consolidation pressure 312 Principles of Engineering Geology 170 160 ~ 150 ~c 140 (II "E 130 z ~ ern= 207.5kN rri2 iii