Feasibility of Ice Segregation Location by Acoustic Emission Detection: A Laboratory Test in Gneiss S. Duca, 1,2 * † C. Occhiena, 2 M. Mattone, 3 L. Sambuelli 4 and C. Scavia 2 1 eni spa, Upstream and Technical Services LAIP, Milan, Italy 2 Department of Structural, Building and Geotechnical Engineering, Politecnico di Torino, Turin, Italy 3 Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Turin, Italy 4 Department of Environment, Land and Infrastructure Engineering, Politecnico di Torino, Turin, Italy ABSTRACT Large slope failures in steep alpine bedrock present significant geological hazards. Ice segregation is thought to be one of the mechanisms involved in high-mountain bedrock fracture but has not been reproduced experimentally in hard, intact rock. Here, we report results from a 3 month freezing experiment that aimed to reproduce ice-lens growth at the interface between the active layer and permafrost in a 15 cm cube of hard, intact rock (Arolla gneiss). Monitor- ing of acoustic emissions (AEs) recorded the propagation of microcracks horizontally through the block, resulting in a continuous and thick macrocrack near the base of the artificial active layer. Microcracking occurred within an ap- proximate temperature range of 0.5 °C to 2.7 °C, consistent with ice segregation theory. Hypocentres of recorded AE events were concentrated in a 40 mm thick band between depths of 4.5 and 8 cm in the block. The band approx- imately coincides with the frozen fringe and indicates that ice segregation can induce micro- and macrocracking in gneiss. Copyright © 2014 John Wiley & Sons, Ltd. KEY WORDS: ice segregation; laboratory test; acoustic emissions; fracturing INTRODUCTION Frost weathering in rock results from the progressive growth of microcracks and relatively large pores wedged open by ice growth (Hallet et al., 1991). Diurnal and annual frost cycles control the timing and magnitude of frost weathering, as highlighted by field monitoring. Porous rock samples have been subjected to bidirectional freezing labo- ratory tests in order to study the onset of fractures contain- ing segregated ice near the permafrost table: the results would seem to imply the development of ice-filled fractures in permafrost bedrock over long timescales (Murton et al., 2001, 2006). This finding, combined with numerical model- ling of the thermal regime in permafrost rock slopes, con- tributes to the prediction of large-scale rockfalls and rock avalanches triggered by permafrost degradation (Matsuoka and Murton, 2008). These authors suggested that future studies of frost weathering should investigate hard, intact rocks, which form high mountains; this will help to address the question ‘Does microgelivation of hard, intact rocks require an extant microcrack system developed by any process or inherited?’ (e.g. Whalley et al., 2004). Labora- tory freeze-thaw tests have never caused the generation and propagation of new, visible cracks in hard, intact rock; they have only revealed a decrease in ultrasonic velocity or Young’s modulus, or a minor increase in porosity (Matsuoka, 1990; Ondrasina et al., 2002; Whalley et al., 2004). Ice segregation theory suggests that cracks in low- porosity rocks such as granite propagate at low temperatures of 4 °C to 15 °C (Walder and Hallet, 1985); previous laboratory simulations have been carried out in high-porosity rocks (tuff and chalk) inducing ice segregation at higher tem- peratures (> 2 °C). In recent years, theoretical studies and laboratory experi- ments have investigated the role of ice segregation in intact rocks (Walder and Hallet, 1985; Akagawa and Fukuda, 1991; Murton et al., 2000, 2006; Chen et al., 2003; Saad et al., 2010). Most laboratory studies use intact rock samples with medium (5–20%) to high (>20%) porosity because intact rocks allow the correlation of rock properties with frost sensitivity, and high-porosity rocks are generally * Correspondence to: S. Duca, eni E&P, Milan, Italy. E-mail: silvia_duca@libero.it † Present address: eni spa Upstream and Technical Services/ LAIP Dpt. Via Maritano, 26 - 20097 S. Donato, Milanese (MI) - Italy PERMAFROST AND PERIGLACIAL PROCESSES Permafrost and Periglac. Process. 25: 208–219 (2014) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ppp.1814 Copyright © 2014 John Wiley & Sons, Ltd. Received 16 October 2013 Revised 4 July 2014 Accepted 11 July 2014