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Acknowledgments to
the Second Edition
We thank our publisher, Taylor & Francis Group, for its encouragement
and support to write this second edition, which shows its great interest
in ground improvement methods. Thanks are also due to Dr.  Wolfgang
Sondermann, the chairman of the German Geotechnical Society and director of Keller Group plc (London, UK) for valuable advice and information
on the international foundation market.
We also thank Dr. Wilhelm Degen of Betterground (Germany) for information on special plant and equipment as well as on the newly developed
quality control and operator guidance system for stone columns.
We are grateful for the support and suggestions given by our former
and present colleagues Johannes Haas of Keller Holding and Nikolaus
Schneider of GuD (Berlin, Germany) on the use and development of the
deep vibratory methods. Information on recent case histories were gratefully provided by Eric Droof and Jim Hussin of Hayward Baker, Hassan
Ahmed and Guido Freitag of Keller Holding, and Jonathan Daramalinggam
and Dr. Venu Raju of Keller Asia.
Special thanks go to Prof. Stavros Savidis, Technical University Berlin,
Germany, who allowed access to Degebo archives, and to Dr. Ralf Glasenapp,
who helped tracing their invaluable documents of the first use of the vibro
compaction method.
Thanks are also due to Christine Trolle of Keller Holding, Michael
Schluchter of GuD and Gunter Raabe of Gr Grafico, who supported us in
designing new line drawings for this book.