Generations of Earth Science students have struggled to visualize the three-dimensional geometry of geological horizons, fabrics, fractures and folds. The stereographic projection is an essential tool in the fields of structural geology and geotechnics, which allows three-dimensional orientation data to be
represented and manipulated. Some existing texts include brief sections on the stereographic method, but do not provide students with an explanation of the underlying principles. This can lead to misuse of the
techniques and results that are drastically incorrect. Stereographic Projection Techniques for Geologists and Civil Engineers has been designed to make the subject as accessible as possible. It gives a straightforward and simple introduction to the subject and, by means of examples, illustrations and exercises, encourages the student to visualize the problems in three dimensions.
The subject is presented in easy-to-manage chapters consisting of pairs of pages, with a page of illustrations facing a page of explanatory text. Students of all levels will be able to work through the book and come away with a clear understanding of how to apply these vital techniques.
This new edition contains additional material on geotechnical applications, improved illustrations and links to useful web resources and software. It will provide students of geology, rock mechanics,
geotechnical and civil engineering with an indispensable guide to the analysis and interpretation of field orientation data.
Author(s): Richard Lisle, Peter Leyshon
Edition: 2nd
Publisher: Cambridge University Press
Year: 2004
Language: English
Pages: 112
City: New York
Preface page vii
Acknowledgements viii
1 Geological structures of planar type 2
2 Measuring and recording the orientation of planar structures 4
3 Geological structures of linear type 6
4 Measuring and recording the orientation of lines 8
5 Why do we need projections? 10
6 Idea of stereographic projection 12
7 Approximate method of plotting lines and planes 14
8 Exercises 1 16
9 The stereographic net 18
10 Precise method for plotting planes. Great circles and poles 20
11 Precise methods for plotting lines 1. Where the plunge of the line is known 22
12 Precise methods for plotting lines 2. Where the line is known from its pitch 24
13 The intersection of two planes 26
14 Plane containing two lines 28
15 Apparent dip 30
16 The angle between two lines 32
17 The angle between two planes 34
18 The plane that bisects the angle between two planes 36
19 Projecting a line onto a plane 38
20 Stereographic and equal-area projections 40
21 The polar net 42
22 Analysing folds 1. Cylindricity and plunge of axis 44
23 Analysing folds 2. Inter-limb angle and axial surface 46
24 Analysing folds 3. Style of folding 48
25 Analysing folds 4. The orientation of folds 50
26 Folds and cleavage 52
27 Analysing folds with cleavage 54
28 Faults 1. Calculating net slip 56
29 Faults 2. Estimating stress directions 58
30 Cones/small circles 60
31 Plotting a cone 62
32 Rotations about a horizontal axis 64
33 Example of rotation about a horizontal axis. Restoration of tilt of beds 66
34 Example of rotation. Restoring palaeocurrents 68
35 Rotation about an inclined axis 70
36 Example of rotation about an inclined axis. Borehole data 72
37 Density contouring on stereograms 74
38 Superposed folding 1 76
39 Superposed folding 2. Sub-area concept 78
40 Example of analysis of folds. Bristol area 80
41 Geometrical analysis of folds. Examples from SW England 82
42 Example of analysis of jointing. Glamorgan coast 84
43 Geotechnical applications. Rock slope stability 86
44 Assessing plane failure. Frictional resistance 88
45 Assessing plane failure. Daylighting 90
46 Assessing wedge failure 92
47 Exercises 2 94
48 Solutions to exercises 97
Appendix 1 Stereographic (Wulff) equatorial net 99
Appendix 2 Equal-area (Lambert/Schmidt) equatorial net 100
Appendix 3 Equal-area polar net 101
Appendix 4 Kalsbeek counting net 102
Appendix 5 Classification chart for fold orientations 103
Appendix 6 Some useful formulae 104
Appendix 7 Alternative method of plotting planes and lines 106
Availability of computer programs for plotting stereograms 108
Further reading 109
Index 110
