Associated research Centers for the Urban Underground Space (ACUUS) is an international, non-governmental organisation, promoting the sustainable use of the underground space.

The ACUUS 2020 Virtual Conference took place in Helsinki, Finland on 3-4 February 2021 and was organized by the International organisation ACUUS, Finnish Tunnelling Association (MTR-FTA), Finnish Association of Architects (SAFA) and Finnish Association of Civil Engineers (RIL). The original dates for this conference were in September 2020. Due to covid-19 travel restrictions, the conference was postponed and it was arranged only virtually. Most of the scientific papers were received before summer holidays 2020 and it would have been unpleasant to postpone publishing these papers any longer.

The conference included 96 presentations altogether. There were three categories of presentations: eight keynote speeches, 68 live presentations and 20 on demand video presentations. The keynotes represented current topics from the underground architecture to the latest developments in using underground space as well as the impact of the covid-19 Pandemic. The live presenters had 12 minutes time for presentation and then three minutes for Q/A.

Moreover, 1400 chat messages were sent between participants during the conference.

This publication consists of 51 accepted scientific papers under the following themes:

Architecture

Urban planning

City development

Underground infrastructures

Design

Reuse of underground space

Sustainability and environment

Geothermal energy

Safety and human factors

Perspectives

Technical approaches and innovations

The ACUUS 2020 conference had 195 participants from 24 countries. The participants in order of magnitude were from Finland, China, Japan, Hong Kong, Sweden, United States, Greece, Russia, United Kingdom, Singapore, Canada, Norway, Switzerland, Australia, Albania, Austria, Belgium, France, India, Iran, Israel, Italy, Serbia and Spain. The ACUUS 2020 conference was broadcasted in two parallel streams by ProspectumLIVE system. The papers were evaluated and reviewed by Ex-Ordo’s management system. The conference was considered very successful based on the participants’ feedback giving mean score of 4.3 (1 poor…5 excellent) for the overall conference experience and the overall technical quality mean score of 4.4.

The ACUUS 2020 conference in Helsinki was the 17^th in its history. The next conference will be held in Singapore in 2023.

We want to take the opportunity to thank the authors of the published articles, the Scientific Committee members for their improving comments to the submitted papers in the review process and all active conference participants for interesting discussions during the sessions and breaks that contributed to the ACUUS 2020 Helsinki success.

Editors

Ilkka Vhaho

Chair of the ACUUS 2020 Scientific Committee

Erik Johansson

Co-chair of the ACUUS 2020 Scientific Committee