Editors’ Note

Abstract

This special issue is dedicated to the state of practice of geothermal foundations, with a particular focus on energy pile foundations. The selection and organization of the seven papers were performed in collaboration with Guney Olgun, Ph.D. (Virginia Tech) and John McCartney, Ph.D. (University of CA, San Diego) with whom we would like to credit the technical leads of the manuscripts. The authors represent a truly international effort from the private sector, academic institutions and governmental agencies of seven different countries on three different continents, namely, the USA, France, Switzerland, Germany, UK, Portugal and Australia. In March 2013, a group of 58 leading researchers from around the world gathered for a special NSF sponsored 3day workshop in Lausanne, Switzerland, to discuss the current status of the relationship between geotechnical engineering and near surface geothermal energy. This issue summarizes the most recent research findings and developments in the field of geothermal pile foundations as presented during the workshop and supplemented by the author’s most recent individual research studies. Beyond highlighting the state of practice in construction and installation and the state-of-the-art in design and development, each paper identifies important areas of improvement, as well as, future research. An overview paper by Olgun and McCartney describes the general principles of thermo active geotechnical systems; Amis et al. discuss the best practice in installation, field testing and laboratory investigations along with the benefits of early project collaboration related to the construction of geothermal systems using specific examples drawn from current practice in the UK. Olgun et al. provide a presentation of the existing guidelines and their implementation in building codes and the need for a uniform design procedure that is sufficiently supported through research data. The discussion also includes incentives for the further advancement of green energy with a particular focus on programs such as BREEAM (the UK) and LEED (the USA). Katzenbach et al. focus on new technologies and materials in near surface geothermal systems, presenting several experimental case studies with accompanying analytical modeling. Laloui et al. study the impact of thermohydromechanical behavior of soils on thermoactive geotechnical systems, and how it affects the performance of thermoactive geotechnical system. Bourne-Webb et al. take a critical look at the analytical capabilities to predict thermal stress and strain response and provide valuable recommendations on how to overcome shortcomings of the existing methods in accurately simulating cyclic heating and cooling effects, transient pore water pressure generation and dissipation, and the effects of radial stress changes. Finally, Nicholson et al. provide a perspective on the sustainability of geothermal systems, discussing the environmental impact and regulations and a life cycle analysis supported by a case study of 61 drilled thermoactive piles. The editors hope you will enjoy this multinational perspective on how to better design this unique geotechnical energy system and welcome any comments and discussions. Anne Lemnitzer and Timothy C. Siegel (Editors-In-Chief) together with Guney Olgun and John McCartney. 2014 DFI Board of Trustees