Alpine Infrastructure Research Articles

Materielle und immaterielle Landschaftsveränderungen. Risikoschutz im alpinen Umfeld

The complex use of the Alps as a settlement area and a sports and leisure environment inevitably lead to the increasing construction of technical and architectural infrastructure to protect against so-called natural hazards. These inevitably have an impact on the landscape and, thus, also on the perception and image of it. The article is dedicated to this nevertheless often neglected part of the alpine infrastructure – the measures and large-scale shoring for the protection against avalanches. Not only the material safety infrastructure is of interest, but also the importance it has for the image and perception of the Alps. The focus is on where the measures for protection against danger not only help to shape the physical landscape but also become part of the cultural construction of the Alps. Three image areas were examined – that of the state institution for avalanche control (Forsttechnischer Dienst für Wildbach- und Lawinenverbauung - WLV), that of marketing, and that of the art system. They show how media intersections are now being found after decades of technical construction and visual communication of the Alps running counter to one another. Today, motifs and image strategies from the field of protection planning are entering the field of advertising images, just as developments and approaches from art and advertising are finding their way into images of security production. Finally, one can assume that advertising images in the Alpine region will appear in the future to feature more frequently elements of safety engineering – to complete the ideal image of the Alps with the construction, in which safety architecture is realized as a cultural resource.

Mass movement susceptibility assessment of alpine infrastructure in the Salzkammergut area, Austria

The alpine infrastructure of trails and huts enables access to the Alps and is an essential element of summer tourism. Mass movements, whose frequency and magnitude are expected to increase due to extreme rainfall events associated with climate change, frequently affect this infrastructure. Alpine associations need to adopt new ways within their management and maintenance to cope with the expected effects. An option is the use of susceptibility maps to assess the impact of mass movements on the alpine infrastructure network at a regional scale. Thus, this study aimed to assess the mass movement susceptibility of alpine hut and trail infrastructure in a popular hiking area in the Salzkammergut region in Austria. Two statistical susceptibility mapping approaches (logistic regression and informative value) were applied, assessed for their accuracy, and compared. The susceptibility of the alpine infrastructure to mass movements was calculated for trails and huts. Field validation was performed in a mass movement hotspot within the study area. The resulting mass movement susceptibility maps show similar patterns for areas with low and high susceptibility for both methods but are influenced by the completeness of the mass movement inventory and the quality of the conditioning factors. Both methods presented a prediction rate above 68%, with a higher rate for the logistic regression method. The informative value, however, presented more reliable results during the field validation. Discussions with Alpine associations show the potential of susceptibility mapping to aid strategic alpine infrastructure management by providing an overview of susceptible alpine trails and huts.

Monitoring and analysis of active rockslide-glacier interactions (Moosfluh, Switzerland)

Valley glaciers have traditionally been expected to significantly influence the stability and movement rates of adjacent paraglacial landslides. However, detailed studies related to the mechanical and displacement interactions between glacier ice and unstable rock slopes are very rare. Here we present a detailed in-situ investigation of the spatial variations of the displacement field of the Great Aletsch Glacier in the surroundings of a large active instability, i.e., the Moosfluh Landslide, a Deep-Seated Gravitational Slope Deformation, with superimposed large (1–5 million m3) secondary rockslides formed during fall 2016. We performed repeat UAV-based photogrammetric surveys during ~3 days (74 h) and applied Digital Image Correlation techniques to record high-resolution surface displacement vector fields of the landslide, stable slopes and adjacent glacier. Our results show that the secondary rockslide adjacent to the glacier is composed of two parts of 1.5 and 2.8 million m3 volume respectively, showing significant differences in mean displacement velocities (0.4 and 0.9 m in 74 h respectively, excluding rapid movements from detached blocks). Both rockslide compartments induce clear deflections of the glacier flow field, moving with a maximum velocity of about 0.3 to 0.4 m in 74 h. This influence is highest near the ice-contact boundary and decreases within a distance of about 100–200 m from the rock slope instability. We investigate the viscous forces at the landslide/glacier contact using a straightforward analytical model for an incompressible rockslide block sliding along a planar, cohesionless surface into ice. These forces are then applied to a slope stability model based on the limit equilibrium concept, representing the real geometry at the interface boundary to quantitatively explore the true buttressing effects of valley glaciers on an already moving slope instability. We show that the viscous ice deformation plays an important role in mediating the displacement velocities of landslides in unstable conditions, while, on the other hand, the slope support from the valley glacier has very little influence on the stability of the investigated rockslides.As most valley glaciers are currently strongly retreating due to global warming, uncovering significant numbers of pre-LIA slope instabilities, this detailed investigation provides important hints on their potential displacement behavior. Understanding the factors controlling landslide velocity is of great importance for hazard analyses and early warning. Hence, this study has implications beyond academic interest, e.g., for the planning and operation of alpine infrastructure, such as cable cars or hydropower systems.

Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Subsurface monitoring of permafrost conditions at depths up to 20–30 m is crucial to assess the safety and reliability of mountain infrastructure, because permafrost degradation critically affects rock slope stability in high mountains. Electrical resistivity tomography (ERT) provides a straightforward tool for monitoring near-surface bedrock permafrost at monthly or longer intervals. But as rockfalls are often prepared over periods of hours or days, ERT for early warning purposes should also detect short-term triggering events such as pressurised water flow. Here, we present the first approach to monitor steep permafrost rock walls quasi-continuously with ERT. We measured ERT every 4 h at the up to 67° steep rock wall below the Kitzsteinhorn cable car, Austria. Wenner datasets (n = 996) were analysed from February 2013 to February 2014 in terms of data stability, raw data characteristics and measurement errors coinciding with potential disturbing factors. Strong resistivity changes coincided with rapid freezing or water inundating rock fractures. Automatically detected periods with large resistivity changes produce ERT time series with low resistivities extending from the bottom upwards during times of snowmelt. We infer that flow of pressurised water in fractures warms the surrounding rock in an upward direction, based on fracture inventories, visual observations of cleftwater and near-surface temperature measurements. We develop a strategy for ERT monitoring suitable for potential early warning systems, where high apparent resistivity changes in 4 h intervals may precede critical hydrostatic events confined by permafrost rocks. Copyright © 2016 John Wiley & Sons, Ltd.

Alpine infrastructure in Central Europe: integral evaluation of wastewater treatment systems at mountain refuges

Planning, construction and operation of onsite wastewater treatment systems at mountain refuges is a challenge. Energy supply, costly transport, limited water resources, unfavourable climate and load variations are only some of the problems that have to be faced. Additionally, legal regulations are different between and even within countries of the Alps. To ensure sustainability, integrated management of the alpine infrastructure management is needed. The energy and water supply and the wastewater and waste disposal systems and the cross-relations between them were analysed for 100 mountain refuges. Wastewater treatment is a main part of the overall 'mountain refuge' system. The data survey and first analyses showed the complex interaction of the wastewater treatment with the other infrastructure. Main criteria for reliable and efficient operation are training, technical support, user friendly control and a relatively simple system set up. Wastewater temperature, alkalinity consumption and high peak loads have to be considered in the planning process. The availability of power in terms of duration and connexion is decisive for the choice of the system. Further, frequency fluctuations may lead to damages to the installed aerators. The type of water source and the type of sanitary equipment influence the wastewater quantity and quality. Biosolids are treated and disposed separately or together with primary or secondary sludge from wastewater treatment dependent on the legal requirements.

Semi-probabilistic design of rockfall protection layers

Increasing rockfall activity in the European Alps raises the need for designing systems protecting Alpine infrastructure. So far, layout of rockfall protection layers was carried out in a quasi-deterministic manner. This paper is concerned with the extension towards a semi-probabilistic design of the thickness of gravel layers covering steel pipelines. Quantities with little scatter such as geometric dimensions and elasto-plastic material constants of steel and gravel are treated as deterministic. By contrast, strongly scattering quantities such as the indentation resistance of gravel, R, and rockfall characteristics including boulder mass m and height of fall h f are considered as probabilistic variables. While 5 and 95% quantiles of R (obtained from statistical evaluation of a series of real-scale impact tests onto gravel) represent probability-based interval bounds for designing the gravel layer thickness, the lack of statistical data from rare rockfall events motivates to follow the philosophy of EUROCODE 1, i.e., to define a design rockfall: m = 10,500 kg and h f = 80 m. Based on this input, a standard burying depth of steel pipelines (H = 1 m) is assessed, by comparing estimates of (i) boulder penetration depth into gravel and of (ii) the maximum impact force, respectively, with corresponding quantities related to a suitable real-scale impact test. This comparison shows the need to increase the height of the gravel overburden. In order to prove that a gravel layer thickness H = 2.7 m is sufficient to prevent the pipeline from inelastic deformations when the structure is hit by the design rockfall, several structural analyses with different values for R are carried out. This is done by means of a validated Finite Element model. As a by-product of the proposed semi-probabilistic design procedure, three different deformation modes of the hit pipeline are identified.

Loading of a Gravel-Buried Steel Pipe Subjected to Rockfall

Increasing rockfall activity in the European Alps has raised the need for designing protection systems for Alpine infrastructure. This paper is concerned with protection of steel pipelines by a gravel overburden of height H. Rockfall-induced loading of such pipes is estimated by means of a three-dimensional, quasi-static, elasto-plastic finite-element (FE) model. Maximum impact forces F and corresponding penetration depths w are estimated based on dimensionless formulas, related to real scale impact tests onto gravel layers. The forces F are applied as surface loads onto the FE model, at a distance (H−w) from the pipe. Material behavior of gravel is represented by a cap model, which is based on pressure-independent linear elasticity and associated plasticity. Related material parameters are identified from acoustic and static material tests. The structural FE model is validated by comparing FE-predicted stresses in the pipe with stresses determined in a real-scale structural experiment. This is reasonable only because the real-scale test is independent of the experiments used for identification of the material parameters used as input for the structural FE model. Satisfactory FE predictions motivate use of the FE model for estimating the loading of the steel pipe in untested scenarios, concerning, e.g., different heights of overburden, or different impact intensities. These estimates show some efficiency of gravel protection systems for modest rockfall, with impact energies well below 3,500kJ.