Alpine permafrost exists at high altitude at lower latitudes, such as in the Swiss Alps. Accelerating climate change, including rising mean annual air temperature and extreme rainfall conditions in alpine regions induces permafrost degradation. The warming of permafrost causes accelerated creep of rock glaciers, due to increased unfrozen water content and higher deformability of the ice phase. Recently, the development of deepening depressions has been observed in several rock glaciers in Switzerland, and the changes in land surface characteristics and drainage systems may initiate slope instabilities in rock glaciers. The main aim of this thesis is to characterise the strength and stiffness of alpine frozen soil in rock glaciers. To this end, the geotechnical response, such as creep and failure of frozen soil was investigated through a triaxial stress path testing programme with novel measurement systems for detecting acoustic emissions and measuring volumetric change. In addition, the resistance to crack initiation and propagation was investigated through a beam bending test programme on rectangular artificially frozen soil specimens, using the acoustic emission measurement system. The evaluation of laboratory tests on artificially frozen soil specimens implied that the development of deep depressions in rock glaciers occurs through differential creep and thermal degradation, and that the rate of deformation has the potential to lead to instabilities in rock glaciers. A comparison of the simulation results with the experimental data demonstrated that the semi-coupled model was successful in simulating the most important aspects of the temperature-dependent stress-strain relationship for the frozen soil behaviour that was measured at the element scale. This thesis contributes to an understanding of the variations in geotechnical response of alpine permafrost, by investigating the behaviour of artificially frozen soil specimens experimentally and numerically with time and temperature under specific stress paths. However, further investigations are necessary to assess the long-term stability of rock glaciers affected by climate change.

Alpine permafrost exists at high altitude at lower latitudes, such as in the Swiss Alps. Accelerating climate change, including rising mean annual air temperature and extreme rainfall conditions in alpine regions induces permafrost degradation. The warming of permafrost causes accelerated creep of rock glaciers, due to increased unfrozen water content and higher deformability of the ice phase. Recently, the development of deepening depressions has been observed in several rock glaciers in Switzerland, and the changes in land surface characteristics and drainage systems may initiate slope instabilities in rock glaciers. The main aim of this thesis is to characterise the strength and stiffness of alpine frozen soil in rock glaciers. To this end, the geotechnical response, such as creep and failure of frozen soil was investigated through a triaxial stress path testing programme with novel measurement systems for detecting acoustic emissions and measuring volumetric change. In addition, the resistance to crack initiation and propagation was investigated through a beam bending test programme on rectangular artificially frozen soil specimens, using the acoustic emission measurement system.

This volume gathers the latest advances, innovations, and applications in the field of geotechnical engineering, as presented by leading researchers and engineers at the 7th Italian National Congress of Geotechnical Researchers (CNRIG 2019), entitled “Geotechnical Research for the Protection and Development of the Territory” (Lecco, Italy, July 3-5, 2019). The congress is intended to promote exchanges on the role of geotechnical research and its findings regarding the protection against natural hazards, design criteria for structures and infrastructures, and the definition of sustainable development strategies. The contributions cover a diverse range of topics, including infrastructural challenges, underground space utilization, and sustainable construction in problematic soils and situations, as well as geo-environmental aspects such as landfills, environmental and energy geotechnics, geotechnical monitoring, and risk assessment and mitigation. Selected by means of a rigorous peer-review process, they will spur novel research directions and foster future multidisciplinary collaborations.

Snow and Ice-Related Hazards, Risks, and Disasters, Second Edition, provides you with the latest scientific developments in sea level rise, permafrost degradation, rock/ice avalanches, glacier surges, glacial lake outburst floods, ice shelf collapses, climate change implications, causality, impacts, preparedness and mitigation. The book takes a geo-scientific approach to the topic while also covering current thinking about directly related social scientific issues that can affect ecosystems and global economies. Special emphasis is placed on the rapidly progressing effects from global warming on the cryosphere, perspectives for the future and latest scientific advances, and technological developments. - Presents the latest research on causality, glacial surges, ice-shelf collapses, sea level rise, climate change implications, and more - Contains numerous tables, maps, diagrams, illustrations and photographs of hazardous processes - Features new insights on the implications of climate change, including increased melting, collapsing, flooding, methane emissions, and sea level rise

On the variability of squeezing behaviour in tunnelling

Knowledge of the performance of river dykes during flooding is necessary when designing governmental assistance plans aimed to reduce both casualties and material damage. This is especially relevant when floods have increased in their frequency during the last decades, together with the resulting material damage and life costs. Most of previous attempts for analyzing dyke breaching during flooding have neglected to consider the soil mechanics component and the influence of infiltration and saturation changes on the failure mechanisms developed in the river dyke. This research project aimed to fill that gap in knowledge by analyzing, in a comprehensive manner, the effect of transient water conditions, represented by successive flood cycles, on the seepage conditions and subsequent breaching of dykes. Therefore, three key sub-projects were carried out: • the analysis of the results from an overflow field test, • the physical modeling of small-scaled models under an enhanced gravity field, • the numerical modeling of the flow response and the resulting stability of both the air- and water-side slopes. The results from the numerical simulations matched accurately with the results obtained with the centrifuge modeling, including the prediction of local instabilities during the flood cycles for those dykes that did not include a toe filter.

Squeezing conditions in tunnelling are characterized by the occurrence of large deformations of the opening or high rock pressure that may overstress the lining. Squeezing is associated with poor quality rock. Tunnelling in squeezing ground involves great uncertainties. It is therefore very important to gain a better understanding of the underlying mechanisms. Triaxial testing is the main source of information in order to understand the mechanical features of squeezing ground. Despite the complexity of the squeezing mechanism and the behaviour observed under relatively simple loading conditions, most of previous research work and engineering design practice considers the ground as a linearly elastic, perfectly plastic material obeying the Mohr-Coulomb yield criterion. While the MC model is capable of predicting the final strength and post-failure volumetric behaviour of the squeezing rock, it cannot map some potentially important pre-failure features or the occasionally observed contractant plastic deformation. In addition, the MC model usually leads to an overestimation of the strength under undrained conditions, which is unsafe for tunnel design. The present thesis mainly addresses the influence of constitutive modelling on predictions about the response of squeezing ground to tunnelling in order to provide some general guidelines for basic engineering analysis. This objective is achieved by investigating the behaviour of squeezing rocks theoretically and experimentally, using samples from several tunnel projects, including the Gotthard base tunnel and the planned Gibraltar strait tunnel.