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Field instrumentation in geotechnical engineering
Cold Regions Science and Technology, 12 (1986) 303-304 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
303
BOOK REVIEW
Field Instrumentation in Geotechnical Engineering, by T.H. Hanna. Trans Tech Publications, P.O. Box 266, D-3392 Clausthal-Zellerfeld, F.R.G., 1985. ISBN 0-87849-054-X. ISSN 0080-9004. 843 pp., $69.50.
Take the case of an engineer (civil, mining, municipal, geological or geotechnical) who has the task of monitoring the stability of a deep foundation during construction and, afterwards, the continuing performance of the structure built thereon. Here is a person who probably knows just enough about inclinometers, extensometers, load cells, strain gages, piezometers, etc. to be dangerous. How can he or she determine what parameter should be measured and with what accuracies? What instrument types would be most suitable and how are they to be installed? Where can these instruments be obtained? Who else has used them and with what success? You could, in the words of the immortal Professor Stengel, "look it up." Professor Tom Hanna of the Civil and Structural Engineering Dept. of the University of Sheffield, England has done just that. Sifting through mountains of periodicals, professional journals, manufacturer brochures, reports and proceedings of symposia, he has compiled his latest volume entitled, Field Instrumentation in Geotechnieal Engineering, containing within its over eight hundred pages, descriptions of just about every gadget devised during the last thirty years. The chapter on load measurement tells more than you'd ever want to know about the various types of load cells available, but if it's strain gages you are interested in, look hard because they are scattered throughout this section and in other parts of the book. The next chapter deals with pore water pressure measurement and gives a comprehensive treatment of all kinds of piezometers, from simple standpipes through Casagrande and double tube hydraulic types to the more sophisticated diaphragm types operating on pneumatic or vibrating wire principles. Problems associated with time lag, negative pressures and partial saturation are covered (resulting in the quite erroneous conclusion that diaphragm type piezometers should be fitted with high air entry filter stones - don't believe it!).
Diaphragm pressure cells for the measurement of stresses at foundation/soil interfaces receive excellent treatment in the next chapter, although you may wonder at the seeming complexity and difficulty of obtaining good results with these devices. In-situ stress measurements in a soil mass using pressure meters is well covered. However, the section on rock stress measurement is woefully inadequate. The section on the measurement of ground movements encompasses surveying techniques, subsurface reference points, bench marks, inverted and hanging pendulums, hydraulic leveling gages, settlement indicators, tape extensometers, borehole extensometers, crack monitors, tilt meters, deflectometers, inclinometers and numerous other devices of surpassing ingenuity. Curiously though, you'd never guess from the lack of emphasis and the brevity of the treatment that inclinometers and extensometers probably make up a half of the dollar volume of all geotechnical instruments in use today. Chapter 6 takes care of miscellaneous instrument types such as Borehole TV Cameras, Rock Core Orientation, Accelerometers, Temperature Sensors, Acoustic Emission, Microseismic Networks, Vibration Monitors and special instruments for Ground Freezing, Radioactive Waste Monitoring and Avalanches. A chapter on case histories follows, in which examples of good practice are given for situations such as foundations, piles, underground structures, tunnels, retaining walls, ground anchors, cofferdams, slopes, embankments and the like. Inevitably, the author displays certain biases which he is at no pains to hide. In the preface he states that the text "has drawn heavily on long established traditions of a few national research laboratories and on the pioneering efforts of several university engineering departments." Needless to say, it is precisely these organizations whose efforts are most likely to be publicized. This isn't necessarily bad, but it does de-emphasize the real world where practitioners of various stripes in conjunction with instrument manufacturers have developed a highly successful range of instruments and installation techniques, accounts of which, for various lamentable reasons, are slow to find their way into the literature. Other biases are towards European rather than
304 U.S. practice and towards soil rather than rock problems, both quite understandable given the author's background. The author recognizes the importance of good installation techniques as the vital ingredient of a successful instrumentation program and he has attempted to stress this at various points throughout the book. The reproduction of comparative tables and analyses gleaned from other authors and from the author's experience are most welcome and leave a taste for more. The extensive reference section should help in following up on particular items of interest.
To sum up, the book will be a source of inspiration for those more inclined towards developing and building their own instruments. For those more interested in getting data, how truly helpful a listing of instrument manufacturers with their addresses would have been. Ah well, you could look it up.
J.B. SELLERS
303
BOOK REVIEW
Field Instrumentation in Geotechnical Engineering, by T.H. Hanna. Trans Tech Publications, P.O. Box 266, D-3392 Clausthal-Zellerfeld, F.R.G., 1985. ISBN 0-87849-054-X. ISSN 0080-9004. 843 pp., $69.50.
Take the case of an engineer (civil, mining, municipal, geological or geotechnical) who has the task of monitoring the stability of a deep foundation during construction and, afterwards, the continuing performance of the structure built thereon. Here is a person who probably knows just enough about inclinometers, extensometers, load cells, strain gages, piezometers, etc. to be dangerous. How can he or she determine what parameter should be measured and with what accuracies? What instrument types would be most suitable and how are they to be installed? Where can these instruments be obtained? Who else has used them and with what success? You could, in the words of the immortal Professor Stengel, "look it up." Professor Tom Hanna of the Civil and Structural Engineering Dept. of the University of Sheffield, England has done just that. Sifting through mountains of periodicals, professional journals, manufacturer brochures, reports and proceedings of symposia, he has compiled his latest volume entitled, Field Instrumentation in Geotechnieal Engineering, containing within its over eight hundred pages, descriptions of just about every gadget devised during the last thirty years. The chapter on load measurement tells more than you'd ever want to know about the various types of load cells available, but if it's strain gages you are interested in, look hard because they are scattered throughout this section and in other parts of the book. The next chapter deals with pore water pressure measurement and gives a comprehensive treatment of all kinds of piezometers, from simple standpipes through Casagrande and double tube hydraulic types to the more sophisticated diaphragm types operating on pneumatic or vibrating wire principles. Problems associated with time lag, negative pressures and partial saturation are covered (resulting in the quite erroneous conclusion that diaphragm type piezometers should be fitted with high air entry filter stones - don't believe it!).
Diaphragm pressure cells for the measurement of stresses at foundation/soil interfaces receive excellent treatment in the next chapter, although you may wonder at the seeming complexity and difficulty of obtaining good results with these devices. In-situ stress measurements in a soil mass using pressure meters is well covered. However, the section on rock stress measurement is woefully inadequate. The section on the measurement of ground movements encompasses surveying techniques, subsurface reference points, bench marks, inverted and hanging pendulums, hydraulic leveling gages, settlement indicators, tape extensometers, borehole extensometers, crack monitors, tilt meters, deflectometers, inclinometers and numerous other devices of surpassing ingenuity. Curiously though, you'd never guess from the lack of emphasis and the brevity of the treatment that inclinometers and extensometers probably make up a half of the dollar volume of all geotechnical instruments in use today. Chapter 6 takes care of miscellaneous instrument types such as Borehole TV Cameras, Rock Core Orientation, Accelerometers, Temperature Sensors, Acoustic Emission, Microseismic Networks, Vibration Monitors and special instruments for Ground Freezing, Radioactive Waste Monitoring and Avalanches. A chapter on case histories follows, in which examples of good practice are given for situations such as foundations, piles, underground structures, tunnels, retaining walls, ground anchors, cofferdams, slopes, embankments and the like. Inevitably, the author displays certain biases which he is at no pains to hide. In the preface he states that the text "has drawn heavily on long established traditions of a few national research laboratories and on the pioneering efforts of several university engineering departments." Needless to say, it is precisely these organizations whose efforts are most likely to be publicized. This isn't necessarily bad, but it does de-emphasize the real world where practitioners of various stripes in conjunction with instrument manufacturers have developed a highly successful range of instruments and installation techniques, accounts of which, for various lamentable reasons, are slow to find their way into the literature. Other biases are towards European rather than
304 U.S. practice and towards soil rather than rock problems, both quite understandable given the author's background. The author recognizes the importance of good installation techniques as the vital ingredient of a successful instrumentation program and he has attempted to stress this at various points throughout the book. The reproduction of comparative tables and analyses gleaned from other authors and from the author's experience are most welcome and leave a taste for more. The extensive reference section should help in following up on particular items of interest.
To sum up, the book will be a source of inspiration for those more inclined towards developing and building their own instruments. For those more interested in getting data, how truly helpful a listing of instrument manufacturers with their addresses would have been. Ah well, you could look it up.
J.B. SELLERS