On behalf of the organizing committee of the 5^th International Symposium on Deformation Characteristics of Geomaterials that was held in Seoul, in September 2011 (IS-Seoul 2011), every participant is welcomed and thanked for their effort and collaboration. IS-Seoul 2011 was prepared under the auspices of the Korean Geotechnical Society (KGS) and the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) – Committee TC101, and based on the success of previous symposia: IS-Hokkaido 1994, IS-Torino 1999, IS-Lyon 2003, and the latest, IS-Atlanta 2008.

The main themes of the 5^th symposium include:

1. Experimental investigations from very small strains to beyond failure

2. Behavior, characterization and modeling of various geomaterials

3. Practical prediction and interpretation of ground response: field observation and case histories

This symposium explores and shares ideas about the complex load-deformation response in geomaterials, including laboratory methods for small and large strains; anisotropy and localization; time-dependent responses in soils; characteristics of treated, unsaturated, and natural geomaterials; applications in field methods; evaluation of field performance in geotechnical structures; and physical and numerical modeling in geomechanics.

During the symposium, 7 novel invited lectures including the first Bishop lecture by Professor Fumio Tatsuoka were provided to review the state of the art, improve knowledge, and shape the future of geotechnical engineering. Total of 182 technical papers were submitted and discussed in this symposium. 17 papers were published in a special issue of a peer-reviewed Soils and Foundations and 165 papers were published in this proceeding to exchange advanced knowledge and ideas in geotechnical engineering and promote the partnership among participants from all over the world.

We would like to express our thanks to all the members of the local organizing committee and international advisory board of IS-Seoul for their sincere effort and intense collaboration. We must give special thanks to Professors Yun-Tae Kim, Junhwan Lee, Yong-Joo Lee, Duhee Park, Seong-Wan Park, and Sung-Sik Park for completing the proceedings and organizing the symposium program. Special thanks are extended to Professor Satoru Shibuya and other core-members of the journal of Soils and Foundations. Mr. Heon-Joon Park and Dr. Ilhan Chang, whose devotion made this workshop successful, are appreciated. Finally, the great support from ISSMGE TC101 headed by Professor Herve Di Benedetto is indelible. Most of all, we want to thank all the authors and participants who contributed to this international symposium, IS-Seoul 2011.

Choong-Ki Chung

Young-Hoon Jung

Hyun-Ki Kim

Jong-Sub Lee

Dong-Soo Kim

Seoul, 1 ~ 3 September 2011