NH3.3

Rock moisture is an understudied factor governing weathering and rockfall. Many weathering processes like hydration, thermal and frost cracking are governed by moisture availability. However, weathering studies have primarily focussed on temperatures. The role of moisture supply has not been given the same attention, also because there is no humidity sensor that meets all requirements for application in rock.

In the sandstone area of Saxony in eastern Germany ("Saxonian Switzerland"), climbing on wet rock poses a safety problem as the sandstone loses stability when saturated. Visitor guidance measures ('rock traffic lights') were implemented to temporarily stop climbing at rocks that are too wet. To accompany this measure, we carried out a pilot study at the Gohrisch sandstone massif, involving moisture measurements in the four cardinal directions at the rockwall base and near the summit of the massif. We used a combination of (a) electrical resistivity electrodes, combined with wind-driven rain collectors; (b) 2D-electrical resistivity (ERT); (c) microwave sensors (MW) with four sensor heads for different penetration depth and (d) Schmidt Hammer (SH) measurements to assess rock stability. All techniques were accompanied by laboratory measurements at rock samples.

Electrical resistivity, MW readings and SH rebound all showed very good correlations with rock moisture in laboratory samples. However, the range of values measured in the field strongly differed from laboratory values so that the calibration curves could not be applied to field data. Presumeably this is due to lithological differences between the fresh quarry samples and the pre-weathered rock faces.  

ERT profiles using adhesive electrodes showed good reliability (RMS error 5-14%). Most sites were slightly wet at the surface, drier at 5-15 cm depth and moderately wet at 20-30 cm depth (1000 – 8000 Ohmm). The site Bottom North was much wetter than all others, and the two top positions were dried out at the surface probably due to wind. This distribution was roughly confirmed by microwave sensor data. Direct correlation between MW and ERT measurements was poor as measurement principle and geometry are very different.

Schmidt Hammer data was very consistent with microwave moisture in the lab (lower rebound at wetter surfaces); however not in the field, where the wetter Bottom North site showed highest rebound values. The summit positions showed significantly lower rebound which we attribute to stronger weathering (more dry-wet cycles). Lab results show that the sandstone loses stability (SH rebound) mainly between 60% and 100% pore saturation. Currently we cannot reliably determine if this saturation was actually reached in the field.

The combined interpretation of all measurements, even if imperfectly calibrated, points to surface-parallel weakness zones that have developed at all sites except of Bottom North which is almost never hit by sunlight. Water supply by rainfall is weak at the almost vertical sites; water rather seems to infiltrate in flat areas and to seep out at the base of the massif. The results help to understand the distribution of dampness in the rock and will be supplemented by continuous monitoring and numerical simulations.

How to cite: Sass, O.: Measuring rock moisture using different techniques in the sandstone area of Saxony, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14871, https://doi.org/10.5194/egusphere-egu21-14871, 2021.

Deep-seated gravitational slope deformations (DSGSD) gained increasing attention in Taiwan due to their catastrophic impacts on lives and infrastructures during Typhoon Morakot in 2009, when over 2700 mm of rainfall in 5 days were recorded. As the main Taiwan island is located on a complex convergent plate boundary, available data suggest that the island’s strong tectonic activity has contributed, along with its subtropical climate and intense human activity, to the onset and destabilization of deep-seated landslides. These are widespread in high-relief mountain areas where Miocene to Eocene meta-sandstone and slate successions outcrop. Slopes at Tienchih (Lalong River of Kaohsiung) and Yakou (few km east in Taitung County) were affected by significant slope collapses and impending instabilities after the heavy precipitation of Typhoon Morakot. This led to severe damages and closure of the South Cross Island Highway No.20, a critical roadway connecting the western and eastern sides of S Taiwan, where continuing slope instability has been observed after 2009. At Tienchih, 240 mm of displacement over an area of 6.7 ha were recorded in 2016 by continuous GPS measurements after a heavy rainfall event. At Yakou, the middle slope sector including the road experienced a major collapse in 2018. At both sites, morpho-structural evidence identified in 1-m resolution LiDAR DEMs suggest that long-term slope deformations occurred well before catastrophic slope destabilization. This is supported by spectacular gravitational deformation structures (i.e. kink folds and shear zones), well exposed at Yakou, and by continuous slow movements detected at Tienchih by multi-temporal TCPInSAR analyses on ALOS/PALSAR images (2007-2011). On the other hand, dense vegetation and limited rock outcrops make an accurate assessment of the geometry, controls, mechanisms and style of activity of these landslides difficult. To overcome this difficulties, we carried out a systematic geomorphological mapping of the two areas through ortho-photos and HRDEMs derived from aerial LiDAR (2012 and 2019), and field surveys to characterize the local structural geology (ductile and brittle features), rock mass strength and gravitational morpho-structures. We performed a local-scale analysis of displacement patterns and rates by combining traditional radar interferometry (D-InSAR on ALOS and Sentinel-1 imagery), improved TCPInSAR analyses, GPS data, Digital Image Correlation between DEMs and change detection analysis of LiDAR point clouds. Our results suggest that long-term progressive failure of slopes was promoted by high tectonically-forced erosion rates and constrained by inherited ductile structures. These preconditioned the location, size and mechanisms of slope sectors more prone to catastrophic failure due to intense rainfall and river bank erosion. A systematic characterization of long-term slope deformation can thus provide key information to assess the hazard related to deep-seated landslides in Taiwan.

How to cite: Agliardi, F., Chen, R., Crippa, C., Yi, D.-C., and Lin, C.-W.: Mechanisms and activity of deep-seated landslides at Tienchih and Yakou (S Taiwan) revealed by structural geology and remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9096, https://doi.org/10.5194/egusphere-egu21-9096, 2021.

Lithology identification and discontinuity mapping are necessary for rockfall hazard assessment in tunnels. However, the restricted exposure and variability of rock face orientation in tunnels ought to be taken into account. Therefore, using Light Detection and Ranging (LiDAR) technique may significantly contribute to this task.

A historical carved tunnel in the Upper Marine Molasse (a poorly consolidated sandstone) of the City of Fribourg (Switzerland) was then investigated by fieldwork and LiDAR. Interestingly, it appears that in addition to joints and layering, some specific sedimentary structures, i.e. cross-bedding, have an important role in the tunnel roof stability. Cross-bedding is a sedimentary structure that can be identified clearly by the geometry of layer within one or more beds in a series of rock strata that does not run parallel to the plane of stratification.

In order to detect and analyse these sedimentary structures, the intensity of the backscattered LiDAR signal is analysed using the Oren-Nayar reflectance model, which considers range, incidence angle, scanned surface geometry (i.e. roughness). It provides corrected values of intensities that make possible to distinguish and identify geometry of cross-beddings in the tunnel.

An analysis of structural discontinuities was also performed using Coltop Software which identified joint sets developed inside the tunnel. Based on this approach, lithology characterizations, orientation of each discontinuity and bedding structures could be identified in point clouds confidently for understanding the mechanisms of potential rockfalls in the tunnel.

How to cite: Choanji, T., wolff, C., Fei, L., Loiotine, L., Gutierrez, A., Sun, C., Derron, M.-H., Carrea, D., and Jaboyedoff, M.: Cross-Bedding and Structural Mapping for Rockfall Assessment of a Tunnel using Hi-Resolution LiDAR (Fribourg, Switzerland), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8179, https://doi.org/10.5194/egusphere-egu21-8179, 2021.

In Alpine areas, deep-seated rockslides are relatively common. They are mostly based on geological and tectonic conditions and triggered by permafrost degradation, snowmelt or heavy rainfall events. A striking example is situated near Laatsch, South Tyrol, at the valley entrance of the Münstertal at close range to the national road SS41 leading to the Swiss border. The activation of the movement occurred in the year 2000, showing a rapid expansion since the year 2012 causing a relocation of the road in 2014.

The U-shaped valley of the Münstertal was formed by glaciers, the valley floor is filled with alluvial sediments. The Mountain ridge runs approx. 2,100 m above the Adriatic Sea, valley floor at approx. 1,000 m above Adriatic Sea. The slope gradient varies between 30 and 50°. The rockslide situated in this slope is approx. 400 m wide, approx. 700 m in height at its longest extension, with a slide surface ca. 50 - 100 m deep summing up to an instable rock volume of approximately 5 to 10 million m³ and monthly average movement rates of 0.1 to 0.55 m.

Geological mapping and analysis were performed for the detailed identification of the cause of failure and occurring failure types such as sliding, falling, toppling and flow. The different gneiss bedrock types mainly consist of Quartz, Feldspar, Muscovite and Calcite, foliation is mainly caused by Muscovite layers. Muscovite-rich shearing planes could also be identified via thin section analysis. The foliation dips with a dip of ca. 10-20° mainly towards Northeast and therefore is orientated towards the slope. Two sets of very steep dipping joins are present deeply fragmenting the rock mass providing starting points or lines for the development of scarp surfaces. Deep weathering of the disintegrated gneiss bed rock could be observed at tectonically induced fracture surfaces. Weathering progresses along scarps and developed tension cracks further eroding and dissembling the rock mass.

Movement analysis of different slabs were performed twice a year using multi-temporal terrestrial laser scanning (TLS) between 2017 and 2020. Along this sliding surface, rock material is transported as individual slabs showing mainly a translational movement behavior with minor internal deformation. These slabs are visually recognizable on site as well as during the analysis of movement rates of laserscanning series measurements.  Main mass transport occurs from upper steep slope areas to areas of lower slope angle within and at the foot of the rockslide. General movement occurs via a basal slip surface with an average thickness of failure volume of approx. 50 to 100 Meters.

Volume of displaced material during accompanied processes of rock fall and rock topple events amounts to 2,000 - 5,000 m³ depending on the size of the event. These types of rock movement mainly take place along outbreak recesses at the rockslide flanks, scarps and at the internal slab margins. These falls and topples can also be detected through several laserscanning measurement series.

How to cite: Voit, K., Fey, C., Rechberger, C., Mair, V., and Zangerl, C.: Geological investigation and movement analysis of the deep-seated compound rockslide Laatsch, South Tyrol, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5622, https://doi.org/10.5194/egusphere-egu21-5622, 2021.

Rock mass damaging investigation is a main research topic in the ambit of rock fall hazard assessment. Roads and railways interruptions, as well as damages of buildings, are among the main inconveniences due to the detachment of unstable sectors of highly jointed rock masses. The contribution of rock mass creep together with natural and anthropic forcings leads to the accumulation of inelastic strain within the rock mass and to the formation of new joints or to the extension and movement of the pre-existing ones. The associated stress release produces tiny vibratory signals (known as microseismic emissions) that can be detected by on-site installed microseismic monitoring networks. Monthly and annual microseismic monitoring data can provide information on seismicity increase over certain periods and on the deterioration of rock properties as the elastic moduli. However, other seismic attributes may support the comprehension of rock mass damaging processes. In particular, the analysis over time of the damping ratio associated with the microseismic emissions could indicate transient and permanent changes within the micro-joint network. This analysis approach has been already conducted on a three-month long microseismic dataset collected at the Acuto field-lab, which is hosted in an abandoned quarry and is mainly exposed to environmental forcings (rainfalls and thermal cycles); moreover, to account also for anthropic vibrations, preliminary studies were carried out on a rock mass located in proximity of a railway. As a further perspective, the investigation of multi-year seismic dataset acquired on unstable rock masses will allow to better inspect the reliability of this analysis approach for rock mass damaging assessment.

How to cite: D'Angiò, D., Lenti, L., and Martino, S.: Rock mass damaging investigation through the analysis of microseismic monitoring data collected on rock masses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13425, https://doi.org/10.5194/egusphere-egu21-13425, 2021.

Forests with a high density and basal area of living trees are known for their function as natural and cost-efficient protection against rockfall. The role of deadwood, however, is less understood. We address this knowledge gap in this contribution as we present the results of repeated real-scale experiments in a) a montane beech-spruce forest with and without deadwood and b) in a subalpine scrub mountain pine-spruce forest with deadwood. We used artificial rocks with either an equant or platy shape, masses between 45 kg and 800 kg (≈ 0.3 m3), and equipped with in-situ sensors to gain insights into rotational velocities and impact-accelerations. Clusters of deadwood and erected root plates reduced the mean runout distance at both study sites. For site a), we found that more rocks were stopped behind lying than living trees and that the stopping effect of deadwood was greater for equant compared to platy rock shapes. Site b) revealed a braking effect of scrub mountain pines for relatively small (45 kg), but also a visible reduction in rotational velocities for the 800 kg rocks sensor stream. We conclude that deadwood must be taken into account in rockfall modeling and the management of rockfall protection forests.

How to cite: Ringenbach, A., Bebi, P., Bartelt, P., and Caviezel, A.: The role of forest deadwood in rockfall protection, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10791, https://doi.org/10.5194/egusphere-egu21-10791, 2021.

Rockfalls are severe and common dangerous events in mountain areas which are strongly controlled by geological and weather conditions. Remotely sensed data allows to identify slowly moving block volumes and to characterize the evolution towards collapse. The commonly adopted approaches for time to failure estimations generally rely on the inverse velocity approach. In this study we investigate the capabilities of a viscoplastic model to simulate the progressive evolution of the block instability with time. We use the monitored time series to calibrate the model parameters and then we pass to the modeling of the entire rockfall events and to the design of mitigation countermeasures. To this aim we study the May 29^th 2018 Gallivaggio rock fall (San Giacomo Filippo, Sondrio, Italy) when about 5,000 m³ of rock detached from a 400 m high cliff, causing considerable damage to the area of the Sanctuary of Gallivaggio and closure of the main mountain route (S.S.36).

The area was monitored by the Regional Environmental  Protection Agency since 2011 by using a ground-based radar (GB-InSAR, LisaLab srl), and it was affected by a 150 m³ rockfall event in the last months of 2019.

GB-InSAR data, multiple laser scanner surveys and drone images of the rock cliff recorded before the event allow to identify the source area, to define and characterize the potentially detachable block volumes and their evolution through time. Thanks to the continuous GB-InSAR monitoring which started well before the event, we calibrated the parameters of a 1d multi-block model whose behaviour is governed by time-dependent visco-plastic constitutive law based on the Perzyna’s approach. This model is subsequently employed to reproduce the mechanical response of the block masses until their detachment from the vertical wall by using different constitutive laws.

At the same time, the comparison between the size distributions of the detached and the deposited blocks and the dust sampling and characterization allowed us to evaluate the degree of comminution due to fragmentation. This information, which is rarely available, made possible to calibrate the fragmentation algorithm of the code HY-STONE, which simulates fragmentation of the falling blocks overcoming a certain energy threshold and the dynamic behaviour of the resulting fragments. We first applied the code to replicate the rockfall events, being able to simulate the large spreading of the block that was impossible to simulate without the fragmentation algorithm. Then we applied this modelling approach for the design of a ditch-embankment countermeasure, simulating different scenarios with and without fragmentation. The results show that fragmentation induces an increase in the number of blocks impacting the embankment, in the heights, and in the velocity, but a decrease of the kinetic energy since each fragment has a smaller mass than the original blocks.

How to cite: Valagussa, A., Dattola, G., Frattini, P., Valbuzzi, E., Villa, A., Agliardi, F., and Crosta, G.: Accelerating phase displacement prediction and 3D rockfall modelling of the large Gallivaggio rockfall, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9731, https://doi.org/10.5194/egusphere-egu21-9731, 2021.

Rockfall is one of the most common hazards in mountain areas causing severe damages to structures/infrastructures and, human lives. For this reason, numerous are the papers published in the last decades on this subject, both introducing reliable approaches to simulate the boulder trajectory and defining design methods for sheltering structures. As is well known, the most popular strategy to simulate the block trajectory and velocity is based on the lumped mass material point approach. This is capable of describing the block trajectory, before either its natural arrest or impact against an artificial/natural obstacle, by suitably considering its interaction with soil/rock materials, interaction always dynamic, very often highly dissipative and defined, according to its nature, as sliding, rolling or impact.

In this framework, this study focusses on impacts and, in particular, on the role of block geometry in affecting the block kinematic response. The problem is approached numerically; by modifying a previously conceived elastic-viscoplastic constitutive model, based on the macro-element concept. and capable of satisfactorily simulating impacts of spherical blocks.

The modified constitutive model relaxes the assumption of spherical block by assuming an ellipsoidal shape and by allowing for the boulder rotation. These two changes make the problem more complex but allow to model more realistically the impact. For the sake of simplicity, the results shown in this work consider the block motion to be planar, but the model already allows to include general three dimensional conditions.

In this work, the model is briefly outlined and the procedure for calibrating the model constitutive parameters described. Then, the results of an extensive parametric analysis, employing constitutive parameters calibrated on experimental data taken from the literature, are discussed. In particular, the role of (i) the inner block orientation, and (ii) the inner impact angle is considered in terms of both kinematic variables and restitution coefficients. Finally, interpolation functions to compute restitution coefficients, once both block shape and inner impact block orientation are known, are provided.

How to cite: Dattola, G., Crosta, G. B., and di Prisco, C. G.: Modeling of the impact of rigid ellipsoidal blocks by means of an elastic-visco-plastic constitutive model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12604, https://doi.org/10.5194/egusphere-egu21-12604, 2021.

A comparative analysis between block propagation experiments and predictive simulations of block trajectories was conducted to evaluate the predictive capacities of block propagation analyses. Approximately one hundred blocks were released on two propagation paths with topographical discontinuities and configurations promoting block rolling. The block propagation was analysed at specific locations of the paths, called evaluation screens. A significant variability of the block velocities was measured at the screens and bimodal distributions of the velocities were observed for the screens located downhill topographical discontinuities.

The comparative analysis between the experimental results and the predictive simulations shows a large variability of the simulations results, that illustrates the uncertainties related with these predictions, done without calibration data. Specific limitations of the block propagation models were shown as regards to the modelling of block propagation similar to rolling motion on soft soils. Finally, the simulations were shown more predictive for extreme velocities than for mean ones and for block passing probabilities.

How to cite: Bourrier, F. and the Members of task A.3.1 of C2ROP project: Benchmark of predictive simulations of block trajectories using field experiments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10215, https://doi.org/10.5194/egusphere-egu21-10215, 2021.

Block propagation models are routinely used for the quantitative assessment of rockfall hazard. In these models, one of the major difficulties is the development of physically consistent and field applicable approaches to model the interaction between the block and the natural terrain. For most of propagation models, a thorough calibration of the input parameters is not available over the wide range of configurations encountered in practice. Consequently, the parameters choice is strongly depending on expert knowledge. In addition, most of models exhibit substantial sensitivity to some parameters, i.e. small changes of these parameters entail large differences in the simulation results.

The trajectory analysis platform Platrock, freely available upon request (contact: franck.bourrier@inrae.fr), allows performing 2D and 3D simulations using both material point rebound models and models, based on non-smooth mechanics, that explicitly account for block shape. This platform provides several simulation tools for detailed analyses of block propagation on study sites.

The possibilities of the predictive capabilities of different block propagation modelling approaches integrated into the Platrock platform have been assessed on a well-documented study site, where a benchmark of propagation models has been done in the context of C2ROP research project. This analysis emphasized the capacities of trajectory analyses to traduce block propagation but also demonstrated their substantial sensitivity to model parameters. The results from these simulations cannot be relevantly interpreted if they are not accompanied with calibration proofs, sensitivity analysis, and detailed interpretation of the results from the expert in charge of the study.

How to cite: Acary, V., Bourrier, F., Toe, D., and Kneib, F.: Comparing different block propagation modelling approaches using the Platrock simulation platform, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10619, https://doi.org/10.5194/egusphere-egu21-10619, 2021.

The past decade has witnessed increasing case studies on the application of 3D discrete element modeling to assess potential rockslide disasters. The assessment is usually based only on the influence area related to kinematic process and final deposition by the simulation. Currently, the hazard of the rockslide-structure interaction is not well defined, and only a few studies have quantality this behavior with a parametric analysis. A dip slope disaster case history on 18 August 1997 in Taiwan was simulated in this study using discrete element method (DEM). The landslide intensely damaged a five-floor building complex of the Lincoln community and caused 28 death. This study first gathered historical aerial images, geology maps of 1:50,000 scale, post-disaster investigation reports, and in-situ photos to clarify the geological and geometry conditions of the dip slope and its spatial relationship to the Lincoln community. Most importantly, a 3D geomechanical model was developed for the numerical study. With the advantage of DEM analysis on large deformation problems, the entire impact process of the dip slope failure was simulated, starting from rock mass sliding to collision and breaking during movement, impacting on the structural buildings and progressive failure of the structures. The simulated results agree well with the field observation after the incident in 1997. The parametric results show that the configuration of the geological discontinuity dominates the magnitude of the potential sliding block, and the rockslide-structure interactions are affected by the relative location between rock slope and buildings and the strengths of rock mass and structure elements. Overall, the 3D DEM-based simulation provides qualitative information on the impact process of the rockslide and the damage states of the building complex. This validated numerical approach can be a valuable tool for assessing the building vulnerability to rockslide with scenario study.

How to cite: Lee, C.-H., Lin, C.-H., and Lin, M.-L.: A Numerical Study of Rockslide-Structure Interactions in a Dip Slope Disaster by 3D Discrete Element Modeling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2431, https://doi.org/10.5194/egusphere-egu21-2431, 2021.

Rockfall modelling draws on the experience of researchers, geologists, engineers and authorities to provide protection solutions for rockfall hazards. Decision making when dealing with rockfalls is aided with sophisticated rockfall models. While there are a number of modelling tools available. The ability to make informed decisions on appropriate protection measures is dependent on the user, available data, scenario setting and post processing of simulation results. Despite the advances in the capabilities of rockfall models, there is often disparity between the state of the art in research and rockfall management in practice. With the use of a series of case studies along roadways in Switzerland, we explore some of the issues and challenges in modelling rockfalls. From defining initial conditions for rockfall simulations, the use of simplified empirical methods and advanced modelling techniques and the need for probabilistic data for design decisions, we provide insights into the application of rockfall modelling in practice.    

How to cite: Glover, J. and Nänni, C.: Challenges in rockfall modelling for roadway management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15575, https://doi.org/10.5194/egusphere-egu21-15575, 2021.

The course "Life Safety" was introduced in higher educational institutions of Russia in the 1990s. It combined information from sanitary medicine, criminology and was aimed at developing self-safety in students. The realities of 2020 required the creation of an anti-virus safety section within the course. The teaching of this problem had experienced in some Russian institutions and universities. This topic is taught to students both through personal contact with the lecturer and on-line. The branch of course is based on the following sections of modern science and practice: 1. Virology, 2. Global ecology, 3. Sanitation and preventive medicine. Teaching contributes to the formation of an objective view of the dangers of viruses in young people, without diminishing or exaggerating the real dangers of infectious diseases. Much attention is paid to the following sections of modern science: 1. The theory of the biosphere by Vladimir Vernadsky, 2. The doctrine of genetic instability and "horizontal transmission", providing informational unity of the biosphere, supported by viruses (Nobel Prize for Barbara McClintoch, 1983). Teaching is combined with practical exercises on the use of personal protective equipment against viral infections. The idea is brought to the students that viruses are a necessary component of the biosphere. They cannot be suffocated and it is impossible to be completely isolated from them. Teaching this course will contribute to improving the health indicators of the population. At the sessions of the European Geosciences Union, it is planned to hold a presentation of programs and teaching textbooks for this course.

How to cite: Voronov, N. and Sapunov, V.: Teaching the basics of anti-virus safety in the course "Life Safety", EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3179, https://doi.org/10.5194/egusphere-egu21-3179, 2021.