Editorial: Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure
Authors: Viana da Fonseca António , Ferreira Cristiana , Baudet Béatrice , Ibraim Erdin , Casagrande Michéle , Nishimura Satoshi 
Published: October 2023

Abstract
This Geotechnical Testing Journal Special Issue on Experimental Investigations from Very Small Strains to Beyond Failure presents selected papers originally submitted to the Eighth International Symposium on Deformation Characteristics of Geomaterials held in Porto, Portugal, from September 3–6, 2023 (IS-Porto 2023). This Symposium aimed at exploring and sharing ideas about the complex stress–strain response of geomaterials, including laboratory methods from very small to large strains; anisotropy and localization; time-dependent response of 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. The Symposium was a three-day event organized by the Faculty of Engineering of the University of Porto, under the auspices of the Technical Committee TC101 Laboratory Stress Strain Strength Testing of Geomaterials of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). This symposium was endorsed by the Portuguese Geotechnical Society (SPG), the Faculty of Engineering of the University of Porto (FEUP), under the activities of the Research Unit Institute of R&D in Structures and Construction (CONSTRUCT) of the Portuguese Foundation for Science and Technology (FCT). Building on the tradition of previous Symposia from Sapporo in 1994 to IS-Glasgow 2019, IS-Porto 2023 brought together more than 240 researchers and practitioners from 37 countries to share their experiences and explore new directions in testing, and in constitutive and numerical modelling of geomaterials. This Special Issue of ASTM International’s Geotechnical Testing Journal assembles eleven papers that illustrate some most recent, innovative, and significant advancements in laboratory equipment and experimental methodologies and procedures for the experimental investigations of soils from very small strains to beyond failure. Although most soil research laboratories are now equipped with the latest technology, in terms of transducers or testing apparatus, the inherent complex nature of soils makes studying them an ongoing challenge. This issue reflects the variety of topics that are still being considered, from difficult terrestrial soils, such as high plasticity stiff sedimentary clays (Sorensen et al. 2023), pumice soils (Hashimoto et al. 2023), gravelly (Nikoonejad and Mohsen Haeri 2023) and residual soils (Cheng and Leong 2023), and mine tailings (Narainsamy et al. 2023), to sampling and testing soils from Mars (Chaparro-López et al. 2023). Characterizing liquefiable soils, particularly partially saturated or gassy soils, and its post-liquefaction behavior continues to remain a subject of investigation, particularly in seismic regions, and is discussed in four papers, with emphasis on the applicability of partial saturation for liquefaction mitigation (Ahmad et al. 2023; Kaminski and Grabe 2023; Mele et al. 2023; Molina-Gómez et al. 2023). Greener methods of soil improvement are also explored, for example, biocementation under chemical damage (Ribeiro et al. 2023). The guest editors of this special issue would like to gratefully acknowledge the dedication and effort of all the authors and peer-reviewers of these papers, and the collaboration of the ASTM Editorial Team in the production of this special issue.