Rockfall Occurrence Research Articles

Computational Geometry-Based Surface Reconstruction for Volume Estimation: A Case Study on Magnitude-Frequency Relations for a LiDAR-Derived Rockfall Inventory

Key to the quantification of rockfall hazard is an understanding of its magnitude-frequency behaviour. Remote sensing has allowed for the accurate observation of rockfall activity, with methods being developed for digitally assembling the monitored occurrences into a rockfall database. A prevalent challenge is the quantification of rockfall volume, whilst fully considering the 3D information stored in each of the extracted rockfall point clouds. Surface reconstruction is utilized to construct a 3D digital surface representation, allowing for an estimation of the volume of space that a point cloud occupies. Given various point cloud imperfections, it is difficult for methods to generate digital surface representations of rockfall with detailed geometry and correct topology. In this study, we tested four different computational geometry-based surface reconstruction methods on a database comprised of 3668 rockfalls. The database was derived from a 5-year LiDAR monitoring campaign of an active rock slope in interior British Columbia, Canada. Each method resulted in a different magnitude-frequency distribution of rockfall. The implications of 3D volume estimation were demonstrated utilizing surface mesh visualization, cumulative magnitude-frequency plots, power-law fitting, and projected annual frequencies of rockfall occurrence. The 3D volume estimation methods caused a notable shift in the magnitude-frequency relations, while the power-law scaling parameters remained relatively similar. We determined that the optimal 3D volume calculation approach is a hybrid methodology comprised of the Power Crust reconstruction and the Alpha Solid reconstruction. The Alpha Solid approach is to be used on small-scale point clouds, characterized with high curvatures relative to their sampling density, which challenge the Power Crust sampling assumptions.

Geomechanical Characterization of a Rock Cliff Hosting a Cultural Heritage through Ground and UAV Rock Mass Surveys for Its Sustainable Fruition

In mountainous areas around the world, dealing with rockfalls means facing some technical survey difficulties due to the low accessibility of areas and the height of slopes. If a cultural heritage is also threatened by such mass movement, the need of specific survey solutions, even in a combined asset, is required. This paper deals with the integration of ground and UAV rock mass surveys aimed at defining the rockfall attitude of an unstable rock cliff sector hosting an example of cultural heritage in tourist area of southern Italy, whose fruition has already been threatened by the occurrence of rockfalls. As an example of the defensive architecture of XII and XIII centuries, the Saracen Castle in Taormina is reached by hundreds of visitors each year, but its access path and the surrounding area are threatened by the unstable condition of the cliff, hosting unstable rock volumes on kinematically critical planes. In order to achieve a reliable geostructural setting of the cliff, aiming at its possible securing through proper mitigation works, ground rock mass surveys could not provide enough information due to the bad accessibility of the rock faces. Therefore, a survey by an Unmanned Aerial Vehicle, with a reliable verified accuracy, was carried out to map the discontinuity planes especially occurring at the highest portions of the cliff, achieving geostructural data of different fronts of the cliff. Ground and aerial data were combined and statistically analyzed to define the main kinematic failure patterns. In this perspective, a critical comparison between the two employed surveying methodologies is proposed herein, highlighting that both approaches are affected by potential and limitations and that the integration of the mutual dataset represents a suitable solution for a complete rock mass characterization in this type of areas. Furthermore, rockfall simulations allowed ascertaining that potential falling blocks would cross the access path to the castle, thus representing a natural threat to the fruition of cultural heritage, thus proving the need of mitigation measures to ensure the safe fruition of the cultural heritage.

Volcanic emission and seismic tremor at Santiaguito, Guatemala: New insights from long-term seismic, infrasound and thermal measurements in 2018–2020

Long-term instrumental monitoring of open-vent volcanoes provides the necessary datasets to characterize volcanic activity and unravel its temporal changes. This is particularly important for active lava domes, which can undergo rapid transitions in behavior over the course of their eruption. Here, we analyzed seismic, acoustic infrasound and thermographic data collected between January 2018 and September 2020 to resolve volcanic processes taking place at the Santiaguito lava dome complex in Guatemala. During this period lava effusion filled the crater of the active Caliente lava dome. The extrusive activity was accompanied by small-to-moderate explosions, prolonged episodes of gas emissions, and occasional rockfalls. Automated algorithms were applied to identify seismic signals associated with different processes and to characterize the temporal evolution of activity. We identified ~70–250 tectonic events per week and detected signals associated with gas-and ash explosions occurring at a rate of ~70–100 events/week. Lava dome growth activity was accompanied by the emplacement of a lava flow along the eastern upper flank of Caliente and seismicity possibly due to the occurrence of rockfalls. We observed episodes of harmonic tremor in seismic and acoustic data associated with sustained gas emissions, estimated to originate at shallow depths of about 500–750 m below the crater. Data indicated that both the recurrence rate of tremor (~10–50 events/week) and its duration (~40–130 min/week) were slightly lower and shorter between January 2019 and March 2020 than in rest of the study period, despite minor variations in explosive activity. Finally, within a period of 11 weeks, between 18 January and 4 April 2018, we found 129 volcano tectonic earthquakes; we were able to locate 10 of them at depths between 1.3 and 2.3 km, ~1.5 km southwest of Caliente. This multi-parametric study provides valuable insights into geophysical signals and associated processes at Santiaguito, helping to resolve temporal occurrence of each event type during protracted effusive-explosive activity.

An integrated approach to investigate climate-driven rockfall occurrence in high alpine slopes: the Bessanese glacial basin, Western Italian Alps

Rockfalls are one of the most common instability processes in high mountains. They represent a relevant issue, both for the risks they represent for (infra) structures and frequentation, and for their potential role as terrestrial indicators of climate change. This study aims to contribute to the growing topic of the relationship between climate change and slope instability at the basin scale. The selected study area is the Bessanese glacial basin (Western Italian Alps) which, since 2016, has been specifically equipped, monitored and investigated for this purpose. In order to provide a broader context for the interpretation of the recent rockfall events and associated climate conditions, a cross-temporal and integrated approach has been adopted. For this purpose, geomorphological investigations (last 100 years), local climate (last 30 years) and near-surface rock/air temperatures analyses, have been carried out. First research outcomes show that rockfalls occurred in two different geomorphological positions: on rock slopes in permafrost condition, facing from NW to NE and/or along the glacier margins, on rock slopes uncovered by the ice in the last decades. Seasonal thaw of the active layer and/or glacier debutressing can be deemed responsible for slope failure preparation. With regard to timing, almost all dated rock falls occurred in summer. For the July events, initiation may have been caused by a combination of rapid snow melt and enhanced seasonal thaw of the active layer due to anomalous high temperatures, and rainfall. August events are, instead, associated with a significant positive temperature anomaly on the quarterly scale, and they can be ascribed to the rapid and/or in depth thaw of the permafrost active layer. According to our findings, we can expect that in the Bessanese glacierized basin, as in similar high mountain areas, climate change will cause an increase of slope instability in the future. To fasten knowledge deepening, we highlight the need for a growth of a network of high elevation experimental sites at the basin scale, and the definition of shared methodological and measurement standards, that would allow a more rapid and effective comparison of data.

Integrating principal component analysis with statistically-based models for analysis of causal factors and landslide susceptibility mapping: A comparative study from the loess plateau area in Shanxi (China)

Landslide susceptibility assessment is an important task in urban planning and risk management. For mountainous areas where multiple types of landslides occur, the differences between landslide types should be considered when mapping landslide susceptibility. The main objective of the present study is to compare the prediction performances of three statistically-based models, namely, information value (IV), logistic regression (LR), and weight of evidence (WOE) models, in susceptibility assessments of different landslide types and to optimize the combination of causal factors. The Loess Plateau area in Shanxi Province, China, was selected as the study area. We prepared a landslide inventory by mapping the detailed spatial distribution of 234 loess landslides and 232 rockfalls in the area. Subsequently, 11 causal factors were considered in the construction of an initial index system for the susceptibility assessments, and corresponding thematic layers were generated in a GIS environment. Principal component analysis was utilized to obtain the relative importance of these layers in causing loess landslides and rockfalls, and nine factors with relatively high weights were selected as the final landslide influencing parameters. The relationships between these parameters and landslide distribution were analyzed using the three aforementioned methods and training samples (75% of landslides). The outcomes were extended to the entire study area to determine landslide susceptibility, and the testing samples (25% of landslides) were used to verify the predictive ability of the models. The results illustrated that rainfall and land use were essential in predicting both loess landslide and rockfall occurrences. The WOE and LR models showed the best performance in rockfall and loess landslide susceptibility assessments, respectively. Both models had an accuracy of more than 80%. If both landslide types were considered as an entire group or if all 11 factors were included in the model, the accuracy decreased.

A 6-year lidar survey reveals enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques

Abstract. Cirque erosion contributes significantly to mountain denudation and is a key element of glaciated mountain topography. Despite long-standing efforts, rates of rockwall retreat and the proportional contributions of low-, mid- and high-magnitude rockfalls have remained poorly constrained. Here, a unique, terrestrial-lidar-derived rockfall inventory (2011–2017) of two glaciated cirques in the Hohe Tauern range, Central Alps, Austria, is analysed. The mean cirque wall retreat rate of 1.9 mm a−1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the lowermost, freshly deglaciated rockwall sections. Retreat rates are significantly elevated over decades subsequent to glacier downwasting. Elongated cirque morphology and recorded cirque wall retreat rates indicate headward erosion is clearly outpacing lateral erosion, most likely due to the cataclinal backwalls, which are prone to large dip-slope failures. The rockfall magnitude–frequency distribution – the first such distribution derived for deglaciating cirques – follows a distinct negative power law over 4 orders of magnitude. Magnitude–frequency distributions in glacier-proximal and glacier-distal rockwall sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. In this paper, the second of two companion pieces, we show how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates a transient signal with decadal-scale exhaustion of rockfall activity immediately following deglaciation crucial for future hazard assessments.

Rainfall and rockfalls in the Canary Islands: assessing a seasonal link

Abstract. Rockfalls are frequent and harmful phenomena occurring in mountain ranges, coastal cliffs, and slope cuts. Although several natural processes occur in their formation and triggering, rainfall is one of the most common causes. The prediction of rock failures is of social significance for civil protection purposes and can rely on the statistical analysis of past rainfall conditions that caused the failures. The paper describes the analysis of information on rainfall-induced rockfalls in Gran Canaria and Tenerife, Canary Islands (Spain). An analysis of the monthly rainfall versus the monthly distribution of rockfalls reveals that they are correlated for most of the year, except in summer, when other triggers act to induce collapses. National and regional catalogs with hourly and daily rainfall measurements are used to reconstruct the cumulated amount (E) and the duration (D) of the rainfall responsible for the rock failures. Adopting a consolidated statistical approach, new ED rainfall thresholds for possible rockfall occurrence and the associated uncertainties are calculated for the two test sites. As far as is known, this is the first attempt to predict this type of failure using the threshold approach. Using the rainfall information, a map of the mean annual rainfall is obtained for Gran Canaria and Tenerife, and it is used to assess the differences between the thresholds. The results of this study are expected to improve the ability to forecast rockfalls in the Canary Islands in view of implementing an early-warning system to mitigate the rockfall hazard and reduce the associated risk.

Climatic and structural controls on Late‐glacial and Holocene rockfall occurrence in high‐elevated rock walls of the Mont Blanc massif (Western Alps)

AbstractIn the Mont Blanc massif (European Western Alps), rockfalls are one of the main natural hazards for alpinists and infrastructure. Rockfall activity after the Little Ice Age is well documented. An increase in frequency during the last three decades is related to permafrost degradation caused by rising air temperatures. In order to understand whether climate exerts a long‐term control on rockfall occurrence, a selection of paleo‐rockfall scars was dated in the Glacier du Géant basin [>3200 m above sea level (a.s.l.)] using terrestrial cosmogenic nuclides. Rockfall occurrence was compared to different climatic and glacial proxies.This study presents 55 new samples (including replicates) and 25 previously‐published ages from nine sampling sites. In total, 62 dated rockfall events display ages ranging from 0.03 ± 0.02 ka to 88.40 ± 7.60 ka. Holocene ages and their uncertainties were used to perform a Kernel density function into a continuous dataset displaying rockfall probability per 100 years. Results highlight four Holocene periods of enhanced rockfall occurrence: (i) c. 7–5.7 ka, related to the Holocene Warm Periods; (ii) c. 4.5–4 ka, related to the Sub‐boreal Warm Period; (iii) c. 2.3–1.6 ka, related to the Roman Warm Period; and (iv) c. 0.9–0.3 ka, related to the Medieval Warm Period and beginning of the Little Ice Age.Laser and photogrammetric three‐dimensional (3D) models of the rock walls were produced to reconstruct the detached volumes from the best‐preserved rockfall scars (≤0.91 ± 0.12 ka). A structural study was carried out at the scale of the Glacier du Géant basin using aerial photographs, and at the scale of four selected rock walls using the 3D models. Two main vertical and one horizontal fracture sets were identified. They correspond respectively to alpine shear zones and veins opened‐up during long‐term exhumation of the Mont Blanc massif.Our study confirms that climate primarily controls rockfall occurrence, and that structural settings, coincident at both the massif and the rock wall scales, control the rock‐wall shapes as well as the geometry and volume of the rockfall events. © 2020 John Wiley & Sons, Ltd.

The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland)

Abstract. Denudation of steep rockwalls is driven by rock fall processes of various sizes and magnitudes. Rockwalls are sensitive to temperature changes mainly because thermo-cryogenic processes weaken bedrock through fracturing, which can precondition the occurrence of rock fall. However, it is still unclear how the fracturing of rock together with cryogenic processes impacts the denudation processes operating on steep rockwalls. In this study, we link data on long-term rockwall denudation rates at the Eiger (Central Swiss Alps) with the local bedrock fabric and the reconstructed temperature conditions at these sites, which depend on the insolation pattern. We then estimate the probability of bedrock for failure through the employment of a theoretical frost cracking model. The results show that the denudation rates are low in the upper part of the NW rockwall, but they are high both in the lower part of the NW rockwall and on the SE face, despite similar bedrock fabric conditions. The frost cracking model predicts a large difference in cracking intensity from ice segregation where the inferred efficiency is low in the upper part of the NW rockwall but relatively large on the lower section of the NW wall and on the SE rock face of the Eiger. We explain this pattern by the differences in insolation and temperature conditions at these sites. Throughout the last millennium, temperatures in bedrock have been very similar to the present. These data thus suggest the occurrence of large contrasts in microclimate between the NW and SE walls of the Eiger, conditioned by differences in insolation. We use these contrasts to explain the relatively low denudation rates in the upper part of the NW rockwall and the rapid denudation in the SW face and in the lower part of the NW rock face where frost cracking is more efficient.

Dating of rockfall damage in trees yields insights into meteorological triggers of process activity in the French Alps

Rockfall release is a rather unpredictable process. As a result, the occurrence of rockfall often threatens humans and (infra)structures. The assessment of potential drivers of rockfall activity therefore remains a major challenge, even if the relative influence of rainfall, snowmelt, or freeze–thaw cycles has long been identified in short‐term monitoring projects. In the absence of longer‐term assessments of rockfall triggers and possible changes thereof, our knowledge of rockfall dynamics remains still lacunary as a result of the persisting scarcity of exhaustive and precise rockfall databases. Over the last decades, several studies have employed growth disturbances (GDs) in tree‐ring series to reconstruct rockfall activity. Paradoxically, these series were only rarely compared to meteorological records. In this study, we capitalize on the homogeneity of a centennial‐old reforestation plot to develop two reconstructions – R1 including only growth suppressions, and R2 based on injuries – with limited biases related to decreasing sample size and changes in exposed diameters back in time. By doing so, our study also and quite clearly highlights the large potential that protection forests have in terms of yielding reliable, multidecadal rockfall reconstructions. From a methodological perspective, we find no synchronicity between R1 and R2, as well as an absence of meteorological controls on rockfall processes in R1. This observation pleads for a careful selection of GDs in future reconstructions. In terms of process dynamics, we demonstrate that summer intense rainfall events (>10 mm day−1) are the main drivers for rockfall activity at our study site. Despite the stringency of our detection procedure, correlations between rockfall activity and meteorological variables remain comparable to those reported in previous studies, as a result of the complexity and multiplicity of triggering factors. We therefore call for a more systematic coupling of tree‐ring analysis with rockfall and microclimatic monitoring in future studies. © 2020 John Wiley & Sons, Ltd.

Reliability analysis and partial safety factors approach for rockfall protection structures

The design of rockfall protection structures must consider several variables, such as the energy and the height of the impacting block. Nevertheless, the statistical distributions of these variables do not follow a predefined law. Reliability analyses aim at finding how the random nature of the parameters describing a structure affects its performance and safety. In the geotechnical framework, generally, the limit states approach is adopted, accounting for the design values of both effects of actions and resistances. The present paper proposes a solution to a time-variant reliability problem to define the design values of the parameters for net fences design, i.e. velocity, mass and trajectory height of the impacting block, accounting for the spreading of their distributions and rockfall occurrence process. The proposed approach is incorporated into the semi-probabilistic design framework and the equivalent partial safety factors of the main variables and the corresponding characteristic values are discussed. The results highlights that the values of the partial safety factors are affected by the ratios between two relevant values of the right-tail of the distributions of height and velocity, i.e. the 99th and the 95th percentiles, and by the parameters of the statistical distribution of the blocks found at the foot of the cliff.

The Seismic Factor in the Excitation of Endogenous and Exogenous Processes on Klyuchevskoi Volcano, Kamchatka

The Klyuchevskoi stratovolcano is one of the largest and most active volcanoes in the world; changes of varying sizes have affected the morphology of its surface during historical time. These rock failures mostly occur in long-lived geologic features, namely, volcano-tectonic chutes. Several researchers have made forecasts of failures based on the relief and morphology of the volcano, the system of tectonic discontinuities within its edifice, the localization of parasitic eruptions, the emplacement of intrusions and dikes that have dissected the edifice, glacier activity on the slopes, and other factors. The part played by seismic activity in the preparation and occurrence of major rockfalls and landslides on the volcano has not been previously studied in its own right. The present paper contains an analysis of Klyuchevskoi seismicity related to eruption periods as a key factor to induce deformation and major rockfalls and landslides due to various causes. According to the spatial distribution of earthquakes and the associated seismic energy, the northwestern and southeastern sectors of the volcano are prone to major collapses. This appears to be due to an extension of the edifice in relation to a north-northeast striking fault that traverses the edifice.

A national rockfall dataset as a tool for analysing the spatial and temporal rockfall occurrence in Germany

AbstractThis study presents an evaluation of a comprehensive dataset with information on about 700 recorded rockfall events in Germany for the first time. The focus is on the analysis of monthly distributions of three rockfall clusters in German low mountain ranges and of three elevation classes to provide an overview of the characteristic seasonal occurrence of rockfalls in Germany. Each rockfall distribution is correlated with records of meteorological station clusters which are representative for the long‐term climate conditions of the particular rockfall cluster and elevation class, respectively. The stored parameters in the dataset (year of occurrence, rock volumes, slope angles, affected objects) are evaluated to complete the extensive and differentiated overview of rockfalls in Germany. The analyses of the distributions of the three rockfall clusters show a distinct event concentration in the winter months. Differences are apparent between the monthly distributions of the elevation classes in which clear peaks are partially visible. Freeze–thaw cycles are considered to be the major trigger of winter rockfalls in Germany. Overall, the presented results may serve as a basis for further studies in the German low mountain ranges. © 2020 John Wiley & Sons, Ltd.

Physical and Mechanical Properties of Gypsum‐Like Rock Materials

In the process of tunnel construction, gypsum rock is often encountered, and the volume of gypsum rock expands when encountering water, which is easy to cause the occurrence of rock fall, collapse, and other disasters, bringing serious challenges to the safe construction of the tunnel. Therefore, in this paper, four groups of samples under different moisture content are tested by ultrasonography, uniaxial compression, conventional triaxial compression, Brazilian splitting, X‐ray diffraction, and SEM, and then the physical and mechanical properties of gypsum rock are studied, and the conclusion is as follows: the density of the water saturated sample, and the longitudinal wave velocity of the natural sample are the highest. Both the water saturation and dehydration conditions have a weakening effect on the remolded sample of high‐strength gypsum powder. The peak intensity of the sample gradually increases with the increase of confining pressure, and the relationship between the peak intensity and confining pressure of the sample conforms to the Coulomb strength criterion. After high‐temperature dehydration, the sample showed obvious plastic softening characteristics. The cohesion and internal friction angle of the sample are closely related to the water content. The cohesion is the largest in the 45°C dehydrated sample, the internal friction angle is the smallest in the saturated sample, whereas the cohesion is the smallest and internal friction is the largest in the high‐temperature dehydrated sample. The characteristics of failure for the natural and 45°C dehydrated samples are almost the same and most samples show shear or shear‐tensile failure. The shear plane begins at the edge of the end face of the sample and exhibits a typical diagonal shear failure. The high‐temperature dehydrated samples are completely broken under uniaxial and triaxial compression conditions. After high‐strength gypsum powder was used to make the remolded sample, the calcium sulfate disappeared, the water content increased, and the main mineral components of the natural and saturated samples were the same. After dehydration at 45°C, the sample began to release structural water and generate SiO2. After high‐temperature dehydration, the hemihydrate gypsum continued to dehydrate and become soluble anhydrous gypsum.

Brief communication: Post-wildfire rockfall risk in the eastern Alps

Abstract. In the eastern Alps, no previous research focused on the impact of wildfires on the occurrence of rockfalls. The investigation of wildfires and post-wildfire rockfalls gains new importance with respect to changes in weather extremes and rapid social developments such as population growth and tourism. The present work describes a wildfire that occurred in August 2018 in a famous world heritage site in Austria. Indicators of fire severity and rockfall occurrence during and after the fire are described.

The Importance of Monitoring Interval for Rockfall Magnitude‐Frequency Estimation

AbstractRockfalls commonly exhibit power law volume‐frequency distributions, where fewer large events are observed relative to more numerous small events. Within most inventories, the smallest rockfalls are the most difficult to detect and so may not be adequately represented. A primary challenge occurs when neighboring events within a single monitoring interval are recorded as one, producing ambiguity in event location, timing, volume, and frequency. Identifying measurement intervals that minimize these uncertainties is therefore essential. To address this, we use an hourly data set comprising 8,987 3‐D point clouds of a cliff that experiences frequent rockfalls. Multiple rockfall inventories are derived from this data set using change detections for the same 10‐month period, but over different monitoring intervals. The power law describing the probability distribution of rockfall volumes is highly sensitive to monitoring interval. The exponent,β, is stable for intervals >12 hr but increases nonlinearly over progressively short timescales. This change is manifested as an increase in observed rockfall numbers, from 1.4 × 103(30 day intervals) to 1.4 × 104(1 hr intervals), and a threefold reduction in mean rockfall volume. When the monitoring interval exceeds 4 hr, the geometry of detected rockfalls becomes increasingly similar to that of blocks defined by rock mass structure. This behavior change reveals a time‐dependent component to rockfall occurrence, where smaller rockfalls (identifiable from more frequent monitoring) are more sensitive to progressive deformation of the rock mass. Acquiring complete inventories and attributing discrete controls over rockfall occurrence may therefore only be achievable with high‐frequency monitoring, dependent upon local lithology.

GIS-Based Rockfall Susceptibility Zoning in Greece

The assessment of rockfall risks on human activities and infrastructure is of great importance. Rock falls pose a significant risk to (a) transportation infrastructure, (b) inhabited areas, and (c) Cultural Heritage sites. The paper presents a method to assess rockfall susceptibility at national scale in Greece, using a simple rating approach and Geographic Information Systems (GIS) techniques. An extensive inventory of rockfalls for the entire country was compiled for the period between 1935 and 2019. The rockfall events that were recorded are those which have mainly occurred as distinct rockfall episodes in natural slopes and have impacted human activities, such as roads, inhabited areas, and archaeological sites. Through a detailed analysis of the recorded data, it was possible to define the factors which determine the occurrence of rockfalls. Based on this analysis, the susceptibility zoning against rockfalls at the national scale was prepared, using a simple rating approach and GIS techniques. The rockfall susceptibility zoning takes into account the following parameters: (a) the slope gradient, (b) the lithology, (c) the annual rainfall intensity, (d) the earthquake intensity, and (e) the active fault presence. Emphasis was given on the study of the earthquake effect as a triggering mechanism of rockfalls. Finally, the temporal and spatial frequency of the recorded events and the impact of rockfalls on infrastructure assets and human activities in Greece were evaluated.

Preliminary geomechanical analysis on limestones in PPSDM Geominerba campus, Padalarang, West Java

The research location is in the PPSDM Geominerba field campus. The campus is located in Padalarang, West Java that is surrounded by the open-pit mining of limestone and marble. This limestone was formed in Oligo-Miocene of Rajamandala Formation. The research objective was to determine the condition of the slopes around the campus based on geomechanical characteristics. Based on field observations, the slope angle in the area is dominated by steep slopes. The rock hardness level is dominated by hard rock with a hardness ranging from 50-100 MPa. Rock Mass Rating shows that the are a is dominated by good rocks. While the S lope Mass Rating calculation show that the maximum slope angle is between 52-75 ° . L evel of deformation and intensive weathering process will reduce the strength of the rock in the future. Several rock fall occurrences on this research area support this assumption . Yet , some local open pit mining area activity near the toe hill of the area need to be concerned regarding the effect of the local rock fall occurrences.

Quantitative relationship between weather seasonality and rock fall occurrences north of Hope, BC, Canada

The relationship between rock falls and weather conditions has been widely recognized and attempts have been made to develop weather-based approaches for rock fall hazard management. This dependency of rock fall occurrences on weather suggests that rock fall trends and their associated risks will vary following climatic changes. In this regard, tools that quantify the relationship of weather seasonality and climate with rock fall trends provide an opportunity to forward model potential variations in rock fall trends considering diverse climate scenarios. This paper illustrates the application of one such tool along a section of a transportation corridor through the Canadian Cordillera. von Mises probability distributions are fitted to monthly trends of precipitation and freeze–thaw cycles and combined to develop a probability density model of rock fall occurrences. The methodology is outlined in detail and the model shown to fit the rock fall database with a correlation coefficient of 0.97. Further, the paper discusses limitations of the approach and potential opportunities for improvement, encouraging the use of the method at other sites and building a robust case study database for further enhancement of the approach.

Analysis of Schmidt hammer rebound test results with repetitive impacts for determining the mechanical characteristics of weathered pyroclastic rock surfaces: a case study along the Isotake coast, Japan

Cliffs located along the Isotake coast, Shimane, Japan, are characterized by the development of indents without rockfalls and by the occurrence of rockfalls without indents—even though these cliffs have the same geology. An analytical method was developed to determine the mechanical properties of the rock surfaces of a coastal cliff. Twenty continuous impact repetitions of a Schmidt hammer were applied normal to the cliff surfaces in each test. The results of the tests (26 with indents and 22 without indents) showed a gradual increase in the rebound value with increasing number of repetitions. A new exponential equation was proposed in this study to describe the features of the weathered surfaces. The changes in the results were well approximated by this equation, and the approximation clearly distinguished between the two types of weathered surfaces, with higher rebound values at the surfaces of the cliffs with indents than at the surface of cliffs without indents. The homogeneity and heterogeneity of the surface and inner body of the cliff rock can also be modelled by the coefficients in this equation.