Potential Rockfall Research Articles

Augmented Reality Mapping of Rock Mass Discontinuities and Rockfall Susceptibility Based on Unmanned Aerial Vehicle Photogrammetry

In rockfall hazard management, the investigation and detection of potential rockfall source areas on rock cliffs by remote-sensing-based susceptibility analysis are of primary importance. However, when the rockfall analysis results are used as feedback to the fieldwork, the irregular slope surface morphology makes it difficult to objectively locate the risk zones of hazard maps on the real slopes, and the problem of straightforward on-site visualization of rockfall susceptibility remains a research gap. This paper presents some of the pioneering studies on the augmented reality (AR) mapping of geospatial information from cyberspace within 2D screens to the physical world for on-site visualization, which directly recognizes the rock mass and superimposes corresponding rock discontinuities and rockfall susceptibility onto the real slopes. A novel method of edge-based tracking of the rock mass target for mobile AR is proposed, where the model edges extracted from unmanned aerial vehicle (UAV) structure-from-motion (SfM) 3D reconstructions are aligned with the corresponding actual rock mass to estimate the camera pose accurately. Specifically, the visually prominent edges of dominant structural planes were first explored and discovered to be a robust visual feature of rock mass for AR tracking. The novel approaches of visual-geometric synthetic image (VGSI) and prominent structural plane (Pro-SP) were developed to extract structural planes with identified prominent edges as 3D template models which could provide a pose estimation reference. An experiment verified that the proposed Pro-SP template model could effectively improve the edge tracking performance and quality, and this approach was relatively robust to the changes of sunlight conditions. A case study was carried out on a typical roadcut cliff in the Mentougou District of Beijing, China. The results validate the scalability of the proposed mobile AR strategy, which is applicable and suitable for cliff-scale fieldwork. The results also demonstrate the feasibility, efficiency, and significance of the geoinformation AR mapping methodology for on-site zoning and locating of potential rockfalls, and providing relevant guidance for subsequent detailed site investigation.

Brief communication: Remotely piloted aircraft systems for rapid emergency response: road exposure to rockfall in Villanova di Accumoli (central Italy)

Abstract. The use of remotely piloted aircraft systems (RPASs) in geosciences is often aimed at the acquisition of an image sequence to produce digital models and orthophotographs of the topographic surface. The technology can be applied for rockfall hazard and risk assessment. To study rockfalls, an approach consists in the application of numerical models for the computation of rockfall trajectories. Data required for such simulations include digital terrain models, location of the instability source areas, and the mechanical properties of the terrain. In this article, we present an analysis of the earthquake-triggered rockfall that occurred along the SP18 in Villanova di Accumoli (Lazio, central Italy) during the seismic sequence that started on 24 August 2016. A survey with a multicopter was carried out to obtain a surface model of the terrain and identify and characterize the source areas and other instable blocks in areas not accessible in the field. The investigated area extends for 6500 m2 and was covered by 161 photographs that were used to obtain an orthophoto with a ground resolution of 2.5 cm and a digital surface model with a ground resolution of 20 cm × 20 cm, which was processed and fused with GNSS real-time kinematic data. To obtain a map of potential rockfall trajectories, we run the numerical model STONE, using as origin of the boulders both source areas mapped in the field and pixels with a slope angle above a selected threshold. Results showed that only the part of the road SP18 already affected by the rockfall was exposed to further rockfall impacts. In particular, it was observed that 29.2 % (i.e. 12 123) of the 41 500 simulated trajectories may potentially reach or cross this tract of the road. Based on these data, limited protection measures were suggested. The combined use of RPAS data, fused with ground GPS points, an accurate geomorphological survey, and terrain static and dynamic parameters from the literature allows fast, low-cost, and replicable rockfall numerical modelling useful for emergency response and adoption of proper protection measures.

Rockfall Source Identification Using a Hybrid Gaussian Mixture-Ensemble Machine Learning Model and LiDAR Data

The availability of high-resolution laser scanning data and advanced machine learning algorithms has enabled an accurate potential rockfall source identification. However, the presence of other mass movements, such as landslides within the same region of interest, poses additional challenges to this task. Thus, this research presents a method based on an integration of Gaussian mixture model (GMM) and ensemble artificial neural network (bagging ANN [BANN]) for automatic detection of potential rockfall sources at Kinta Valley area, Malaysia. The GMM was utilised to determine slope angle thresholds of various geomorphological units. Different algorithms (ANN, support vector machine [SVM] and k nearest neighbour [kNN]) were individually tested with various ensemble models (bagging, voting and boosting). Grid search method was adopted to optimise the hyperparameters of the investigated base models. The proposed model achieves excellent results with success and prediction accuracies at 95% and 94%, respectively. In addition, this technique has achieved excellent accuracies (ROC = 95%) over other methods used. Moreover, the proposed model has achieved the optimal prediction accuracies (92%) on the basis of testing data, thereby indicating that the model can be generalised and replicated in different regions, and the proposed method can be applied to various landslide studies.

Influence of digital elevation model resolution on rockfall modelling

Spatial models are an effective tool for determining potential rockfall source, transit and deposit areas. The reliability of the final rockfall modelling results depends on the quality of the input data, which is mostly based on the digital elevation model (DEM). The spatial resolution of the DEM holds key information about the main morphological properties of the surface, which is crucially important when modelling this kind of geomorphological phenomenon. Therefore, this article studies the influence of DEM spatial resolution on the modelling of rockfall source, transit and deposit areas. Modelling was carried out at five different DEM spatial resolutions available for Slovenia (1 m, 5 m, 12.5 m, 25 m and 100 m). Rockfall source areas were identified using a geomorphometric approach based on a high resolution DEM and a geographical information system. Rockfall transit and deposit areas were modelled using the Conefall computer program, which is designed to estimate potential rockfall risk areas. The area of study was the municipality of Vipava (107.4 km2) in Slovenia, EU. A spatial resolution of 1 m was chosen as a reference layer to which all modelling results of the other spatial resolutions were compared. Validation of modelling included rockfall source area comparison with orthorectified aerial images and location collection of silent witnesses (rock deposits) in the field for estimating maximum runout zones. The modelling results indicate that a spatial resolution of 1 m is the most suitable for modelling on a local scale; resolutions of 5, 12.5 and 25 m can be used for modelling on a regional scale (depending on the purpose of the modelling results); and a resolution of 100 m should not be used for rockfall modelling. Major differences between spatial resolutions can be observed when modelling rockfall source areas, i.e. in areas with the most diverse topography, while in deposit areas the observed differences are smaller due to the less rugged surface.

Evaluation of Rockfall-hazard Potential For Rockville, Utah, Following a 2013 Fatal Rockfall

Abstract In December 2013, a rockfall in the town of Rockville, Utah, released an estimated 2,700 tons (2,450 tonnes) of rock from a 400-ft (122-m) high slope; the rock struck a house at the base of the slope, resulting in two fatalities. We performed detailed field and laboratory investigations to (1) identify the modes of failure and factors contributing to rockfalls along the east-west trending, south-facing slope where it passes through the town; (2) identify sections of the slope that pose the highest hazard for future property damage or injury; and (3) suggest potential remedial measures. Field investigations included mapping discontinuities, establishing stratigraphy, measuring slope geometry, and evaluating potential failure modes at four selected sites. Laboratory investigations included determining dry density, friction angle, and slake durability index of rock samples. Using the Dips software, we determined the principal joint sets and performed a kinematic analysis. The maximum rollout distances for rock blocks of various sizes were determined for each of the study sites using the RocFall software. Results of the kinematic analysis and field observations indicate that wedge, plane, and toppling failures are possible within the Shinarump Conglomerate Member of the Chinle Formation and the Upper Red Member of the Moenkopi Formation along the entire slope. Based on the results of the study, we developed a rockfall-hazard map that indicates that the western portion of the town faces the highest hazard from potential rockfalls. The most feasible future remedial measure is not to build close to the hazardous slopes. Other possible remedial measures include removing loose rock blocks, installing rock anchors, and using drapery mesh.

A hybrid model using machine learning methods and GIS for potential rockfall source identification from airborne laser scanning data

The main objectives of this paper are to design and evaluate a hybrid approach based on Gaussian mixture model (GMM) and random forest (RF) for detecting rockfall source areas using airborne laser scanning data. The former model was used to calculate automatically slope angle thresholds for different type of landslides such as shallow, translational, rotational, rotational-translational, complex, debris flow, and rockfalls. After calculating the slope angle thresholds, a homogenous morphometric land use area (HMLA) was constructed to improve the performance of the model computations and reduce the sensitivity of the model to the variations in different conditioning factors. After that, the support vector machine (SVM) was applied in addition to backward elimination (BE) to select and rank the conditioning factors considering the type of landslides. Then, different machine learning methods [artificial neural network (ANN), logistic regression (LR), and random forest (RF) were trained with the selected best factors and previously prepared inventory datasets. The best fit method (RF) was then used to generate the probability maps and then the source areas were detected by combining the slope raster (reclassified according to the thresholds found by the GMM model) and the probability maps. The accuracy assessment shows that the proposed hybrid model could detect the potential rockfalls with an accuracy of 0.92 based on training data and 0.96 on validation data. Overall, the proposed model is an efficient model for identifying rockfall source areas in the presence of other types of landslides with an accepted generalization performance.

Rockfall Analysis for Preliminary Hazard Assessment of the Cliff of Taormina Saracen Castle (Sicily)

A rockfall analysis at one of the most relevant cultural heritage sites of northeastern Sicily (Italy) is presented herein with the aim of assessing the hazard arising from the unstable conditions of the rock cliff of Taormina city, upon which the Saracen Castle is perched on its top. Several rockfalls affected this area in the latest years, representing a serious threat for the safety of inhabitants and tourists. Therefore, the qualitative Evolving Rockfall Hazard Assessment (ERHA) was applied for the hazard zonation, supported by rock mass surveys and Terrestrial Laser Scanner prospecting. Kinematic analysis revealed that the unstable rock failure patterns are represented by planar/wedge sliding and toppling, while simulation of potential rockfalls allowed studying the impact of future events in terms of trajectory and energy. This is higher at the foot of scarps and in steeper sectors, where the application of ERHA identified a critical zone close to the inhabited center, which is one of the main elements at risk, along with a pedestrian tourist path. Achieved results represent a starting point for the definition of risk management strategies and provide a scientific contribution to the study of hazard and risk arising from rockfall occurrence.

2D and 3D Rockfall Hazard Analysis and Protection Measures for Saptashrungi Gad Temple, Vani, Nashik, Maharashtra – A Case Study

ABSTRACT The Saptashrungi gad temple (SGT) situated on basaltic hills belongs to Deccan volcanic of Upper Cretaceous to Lower Eocene, is one among the 51 Shakti Peeths and most holy place for pilgrims. Rockfall is a major problem in the past and causing danger to the lives of the villagers settled at the toe of the SGT hill as well as the pilgrims who perform parikrama along the tracks. On the evening of 16 April 2011, an old woman died due to rockfall at SGT hill when she was performing parikrama, moreover, two persons got injured during the deliverance process of this old woman from the continuous rockfall activity. The problem of rockfall could be linked to rainfall, jointing, weathering, man-made or the compounding of all. In this research, the rockfall hazard analysis at SGT hill is assessed using both 2D and 3D rockfall programs along the two parikrama paths: Parikrama Path 1 (or the Badi Parikrama Path ‘BPP’), and Parikrama Path 2 (or the Chhoti Parikrama Path ‘CPP’). Also, the study area of the SGT hill has been divided into eight zones (Zone#01 to Zone#08), based on field observations, orientations of joint sets and hill slope faces and eighteen topographic profiles (AA’ to RR’) have been taken from these eight zones for rockfall analysis. A detailed topographic survey along with field investigation has been carried out along the temple for ascertaining the nature of rock, discontinuity orientations, and slope geometry. DEM has been generated using topographic profile in ArcGIS to facilitate the 3D rockfall analysis. Maximum rock block sizes are taken into the analysis and run-out distance, bounce height, kinetic energy and velocity of the basaltic blocks are evaluated separately. Based on the analyzed data, the rockfall hazard zone map has been prepared and site having potential rockfall risks have been identified. Finally, wire/net meshing has been proposed after removal of unstable blocks as a stabilization and protection measures. It is worth mentioning here that for the first time rockfall hazard assessment was made in such detail for a site. Suggestions made are implemented by the State Government for the protection of the temple as well as the life of pilgrims performing the parikrama from the rockfall.

Seismic monitoring of small alpine rockfalls – validity, precision and limitations

Abstract. Rockfall in deglaciated mountain valleys is perhaps the most important post-glacial geomorphic process for determining the rates and patterns of valley wall erosion. Furthermore, rockfall poses a significant hazard to inhabitants and motivates monitoring efforts in populated areas. Traditional rockfall detection methods, such as aerial photography and terrestrial laser scanning (TLS) data evaluation, provide constraints on the location and released volume of rock but have limitations due to significant time lags or integration times between surveys, and deliver limited information on rockfall triggering mechanisms and the dynamics of individual events. Environmental seismology, the study of seismic signals emitted by processes at the Earth's surface, provides a complementary solution to these shortcomings. However, this approach is predominantly limited by the strength of the signals emitted by a source and their transformation and attenuation towards receivers. To test the ability of seismic methods to identify and locate small rockfalls, and to characterise their dynamics, we surveyed a 2.16 km2 large, near-vertical cliff section of the Lauterbrunnen Valley in the Swiss Alps with a TLS device and six broadband seismometers. During 37 days in autumn 2014, 10 TLS-detected rockfalls with volumes ranging from 0.053 ± 0.004 to 2.338 ± 0.085 m3 were independently detected and located by the seismic approach, with a deviation of 81−29+59 m (about 7 % of the average inter-station distance of the seismometer network). Further potential rockfalls were detected outside the TLS-surveyed cliff area. The onset of individual events can be determined within a few milliseconds, and their dynamics can be resolved into distinct phases, such as detachment, free fall, intermittent impact, fragmentation, arrival at the talus slope and subsequent slope activity. The small rockfall volumes in this area require significant supervision during data processing: 2175 initially picked potential events reduced to 511 potential events after applying automatic rejection criteria. The 511 events needed to be inspected manually to reveal 19 short earthquakes and 37 potential rockfalls, including the 10 TLS-detected events. Rockfall volume does not show a relationship with released seismic energy or peak amplitude at this spatial scale due to the dominance of other, process-inherent factors, such as fall height, degree of fragmentation, and subsequent talus slope activity. The combination of TLS and environmental seismology provides, despite the significant amount of manual data processing, a detailed validation of seismic detection of small volume rockfalls, and revealed unprecedented temporal, spatial and geometric details about rockfalls in steep mountainous terrain.

Beyond the boundaries of feasible engineering geological solutions: stability considerations of the spectacular Red Beach cliffs on Santorini Island, Greece

The outstanding Red Beach in Santorini, a famous volcanic island in the Aegean Sea in the territory of Greece, exhibits extended rockfall instabilities along its cliffs, placing its highly frequented touristic zones at high risk. This study aimed to generate an engineering geological interpretation of these instabilities and to evaluate the degree of the rockfall potential in relation to the natural evolution of the beach. A detailed field survey of the engineering geological conditions and thorough scanning of the cliffs using terrestrial scanning (LiDAR) combined with accurate geodetic survey facade plans, enabled the detection of cinematically unstable sections. A semiautomated qualitative method for evaluating the site-specific landslide potential was also performed here using an unmanned aerial vehicle, which executed several flights around the research area 3.5 years after LiDAR scanning. The resulting products, namely a digital surface model, an orthophotograph and point clouds, were compared with the LiDAR data to evaluate the behavior of the volcanic formations at the cliff and the rockfall potential. The Red Beach cliff, mainly composed of volcanic scoria cones, was found to be very challenging case for determining a feasible engineering geological solution. Its numerous requirements with respect to rockfall control and stabilization in conjunction with the necessity of maintaining the landscape’s natural beauty and preserving the adjacent archeological site further complicated the problem. However, stabilization to prevent rock falls will provoke a disruption of the balance between the sea-induced erosion and the supply of material that originates from rock falls of the natural slopes toward the beach that could put the existence of the Red Beach in significant danger. A feasible engineering geological solution for stabilizing the cliffs was investigated by evaluating all the possible protective and prevent measures. However, whether any of these measures are acceptable is doubtful.

Managing rockfall risk through baseline monitoring of precursors using a terrestrial laser scanner

Rockfalls represent significant risks to safe and efficient use of transportation corridors. In this paper, we address the management of rockfall risk through baseline remote monitoring of susceptible slopes (every 2–4 months) along a transportation corridor along the Fraser River valley in western Canada using a terrestrial laser scanner and supporting remote sensing technologies. This includes identifying potential rockfall source zones based on incipient signs of failure, tracking kinematics in three dimensions to better understand the mechanism of failure, estimating potential failure volumes based on bounding joint structure, and transmitting this information to the railway operator for an assessment of risk. We demonstrate our approach for one case along the line where we identified several potential failures ranging in volume from 48 to 4200 m3. Our projections of the location of failures were successful, in that volume projections were within 10%–55%, and the anticipated kinematics and failure mechanism were consistent with the assessment of post-failure rockfall scar geometries. Accurate volume and kinematics estimates are important for the assessment of hazard and risk as well as the planning of risk mitigation options. In general, this approach can be used to better manage risk from rockfall hazard in communities, transportation corridors, or other infrastructure.

Monitoring rock reinforcement works with ambient vibrations: La Bourne case study (Vercors, France)

This study uses ambient vibrations to monitor rock bolting works, the efficacy of which is usually difficult to estimate. The test site is a 760m3 unstable limestone column located in the Bourne valley (Vercors, France). The rock column's resonance frequencies (fX) were identified, corrected for reversible thermal effects and monitored over time. We observed clear increases in fX up to ~17% resulting from the additional stiffness provided by the steel rock bolts. Numerical modeling helped to confirm that the rebar elements were grouted on both sides of the fracture. The major column's resonance features, such as the resonance frequencies and mode shapes, were successfully simulated, including their evolution with bolting. The amount of fX increase depends on the mode considered, likely controlled by bolt location in comparison with the modal shape. This study confirms the potential of ambient vibrations to provide global in-depth information on the stability evolution of rock compartments, with versatile applications for monitoring potential rockfalls or reinforcement works.

Analysis of Potential Rockfalls on a Highway at High Slopes in Cold-Arid Areas (Northwest Xinjiang, China)

In the steep mountainous areas in northwest Xinjiang, where rock mass is broken seriously due to intense freeze thaw weathering, rockfall is one of the most common geological hazards on highway high slopes. Engineering geological investigations on geological hazards along a segment of the G219 highway was conducted, indicating that rockfalls on the high slopes threaten the safety of vehicles on the highway seriously. In this study, a combination of field investigations, laboratory experiments and numerical simulation methods was performed to identify unstable high slopes, simulate the rockfall trajectories and assess the rockfall hazard in the study area. The results show that there are five high slopes (i.e., W01, W02, …, W05) where rockfall hazard is extremely serious. Considering both the total kinetic energy and the accumulation rate of blocks, rockfall influence area zonation was performed, leading to the conclusions that the sections of highway on W01 to W05 are located at the medium-intensity low-accumulation zone, high-intensity medium-accumulation zone, high-intensity low-accumulation zone, high-intensity low-accumulation zone and medium-intensity high-accumulation zone, respectively. Based on the analysis, a zonation map was accomplished, which could help engineers select effective mitigation measures against rockfalls to avoid casualty and property losses.

Evaluation of automated underground mapping solutions for mining and civil engineering applications

The extractive and construction industries rely heavily on accurate geospatial data to control position, location, alignment, and orientation of planned excavations. Recent advancements in the survey industry, through the use of terrestrial laser scanning, can now provide engineering teams with three-dimensional (3-D) data in unprecedented detail via georeferenced point clouds. Furthermore, equipment is now available that provides fully mobile automated mapping solutions, independent of satellite positioning, utilizing simultaneous localization and mapping. This paper evaluates the surveying capability of three fully mobile automated mapping solutions against a benchmark laser scanning survey undertaken at the underground Camborne School of Mines Test Mine facility. The study highlights that handheld automated mapping solutions, in which closed-loops can be formed, have the potential to provide quicker data collection and processing time, as well as the required accuracy for underground surveying applications. However, the automated solution was unable to produce the necessary point cloud density to identify low-angled discontinuities that may have a major safety implication, leading to potential rockfall.

Definition and mapping of potential rockfall source and propagation areas at a regional scale in Basilicata region (Southern Italy)

An overview of the more interesting results of the rockfall source areas and propagation obtained in different zones (Province of Potenza) of Basilicata Region is presented and discussed. Basilicata Region is considered one of the regions in the Mediterranean basin most subject to slope instability. In particular, rockfalls constitute a major hazard in numerous rock cuts in such mountainous area, giving rise to casualties, damages and injuries. For mapping of rockfalls susceptibility, it has been possible to calculate the source areas and the propagation. Slope Angle Distribution procedure (SAD) has been adopted to assess the potential rockfall source areas: it allows to show the characteristic of morphological units, such as rock cliffs, steep slopes, footslopes and plains. Potential rockfall source areas are identified by a threshold angle (above the morphological unit steep slopes). Then rockfalls spreading area is assessed using GIS and process-based software: Flow-R (Flow assessment at a Regional Scale). The limit of the applied method is due to the unavailability of high resolution DEM of the study area, nevertheless potential rockfall source areas are identified through the slope angle distribution deduced from geological and topographic maps GIS format.

A stability assessment of the rockfall problem around the Gökgöl Tunnel (Zonguldak, Turkey)

The stability of rock slopes is an important area of interest in civil and mining engineering. This study investigated rockfall occurring around the Gokgol tunnel along the Zonguldak-Ankara roadway. Extensive field studies, including determination of geological description of the rock mass, scan-line surveys on discontinuities, identification of slope profiles, measurement of actual fallen block dimensions, and sampling procedures, were carried out. The study area and its surroundings are part of a Lower Carboniferous limestone formation. The assessments based on field studies indicated that two joint sets and a bedding plane were the main types of discontinuity. Two slope profiles were then created by considering the most frequently encountered rock fall events. The present study aimed to investigate the rockfall potential in this area by means of numerical analyses. For this purpose, RocFall software based on the lumped-mass method was utilized. Based on these analyses, traffic safety is threatened by potential rockfall. In Case I, a 30 % portion of the falling blocks reached the side of the main road, while about 70 % of them remained on the slope. However, falling blocks reached the end of the road in Case II. The study area requires some protection measures, such as the construction of retaining barriers and steel mesh to hold small size rock blocks. As a result, barrier heights to hold falling blocks were calculated as 0.5 m and 4 m for Case I and Case II, respectively. Barrier heights sufficient to hold falling rocks were determined using numerical analysis. In Case II, from such analyses, the energy required for a protection barrier for 1000 kg was found to be 200 kJ.

Rockfall at the heritage site of the Tatlarin Underground City (Cappadocia, Turkey)

Cappadocia is one of the most important natural, historical and cultural heritages of Turkey. The region is seriously threatened by different instability problems, and several locations were accordingly closed to visit, mainly because of rockfalls. The aim of current study is to investigate the rockfall hazard potential near the Tatlarin Underground City. For this purpose, an extensive engineering geological investigation was performed and complemented with a set of rockfall simulations performed by means of the 3D numerical model HY-STONE. The investigation included: (1) mapping of the lithological units (tuffs and overlying basalts, talus deposits) and of unstable blocks along the cliff; (2) rock mass geomechanics and kinematic analysis of block stability; and (3) laboratory testing of tuff and basalt. These allowed to show that the instabilities are mainly controlled by different durability of tuffs and basalts. The weakness of tuffs facilitates a progressive undercutting of the basalt layer, the opening of subvertical joints and the consequent movement of large basaltic blocks. Two future potential rockfall scenarios have been produced by 3D rockfall modelling for hazard zonation and for suggesting risk management strategies. Model parameters were calibrated by back-analysis of both historical events and field tests. Different sets of parameters have been calibrated for different release volumes to consider different degrees of interaction with slope material of different size. The effect of roughness of the topography was investigated in terms of trajectories and lateral dispersion of blocks and its consequences on hazard zonation and risk management actions.

Cut Slope Design for Stratigraphic Sequences Subject to Differential Weathering: A Case Study from Ohio

Designing cut slopes along Ohio highways depends on local stratigraphy and slope stability problems. Based on stratigraphy and modes of failure, cut slopes in Ohio were divided into three types: 1) those consisting of strong rock units (sandstones and limestones) that exhibit discontinuity-related failures; 2) those consisting of weak rock units (shales, claystones, and mudstones) that exhibit raveling, gully erosion, and rotational sliding; and 3) those consisting of interlayered strong and weak rock units where differential weathering causes undercutting-induced failures. Data regarding geological, geotechnical, and geometrical parameters were collected for 26 sites representing the three types of slopes and were used to perform kinematic analysis, rockfall trajectory simulations, and global stability analysis. This article focuses on the design of cut slopes in interlayered stratigraphy where differential weathering is the primary cause of slope instability. Based on stratigraphic variations, we categorized cut slopes in the interlayered units into four types: Type I—thick sandstone underlain by thick shale or claystone/mudstone; Type II—sandstone interlayered with shale or claystone/mudstone in nearly equal proportions; Type III—limestone interlayered with claystone/mudstone in nearly equal proportions; and Type IV—claystone/mudstone interlayered with minor, thin limestone layers. Based on stability analyses and rockfall simulations, we recommend cut slope designs for each stratigraphic sequence that consider slope angles for undercut units to reduce rockfall potential, slope angles for undercutting units that are close to naturally stable angles, benches to reduce undercutting and contain rockfalls, drainage to reduce erosion, and catchment ditches to contain rockfalls.

Integrating field measurements, a geomorphological map and stochastic modelling to estimate the spatially distributed rockfall sediment budget of the Upper Kaunertal, Austrian Central Alps

The estimation of catchment-scale rockfall rates relies on the regionalisation of local measurements. Here, we propose a new framework for such a regionalisation by the example of a case study in the Upper Kaunertal, Austrian Central Alps (62.5km2). Measurements of rockfall deposition during 12months onto six collector nets within the study area were combined with published mean annual rates from the literature, and a probability density function was fitted to these data. A numerical model involving a random walk routing scheme and a one-parameter friction model was used to simulate rockfall trajectories, starting from potential rockfall source areas that were delineated from a digital elevation model. Rockfall rates sampled from the fitted probability density function were assigned to these trajectories in order to model the spatial distribution and to estimate the amount of rockfall deposition. By recording all trajectories as edges of a network of raster cells, and by aggregating the latter to landforms (or landform types) as delineated in a geomorphological map of the study area, rockfall sediment flux from sources to different landforms could be quantified. Specifically, the geomorphic coupling of rockfall sources to storage landforms and the glacial and fluvial sediment cascade was investigated using this network model. The total rockfall contribution to the sediment budget of the Upper Kaunertal is estimated at c. 8000Mgyr−1, 16.5% of which is delivered to the glaciers, and hence to the proglacial zone.The network approach is favourable, for example because multiple scenarios (involving different probability density functions) can be calculated on the basis of the same set of trajectories, and because deposits can be back-linked to their respective sources. While the methodological framework constitutes the main aim of our paper, we also discuss how the estimation of the budget can be improved on the basis of spatially distributed production rates.

Experience with the development and use of a simple DFN approach over a period of 30 years

A contractual dispute on a tunnelling project more than 30 years ago was the impetus for the development of a program to generate discontinuity patterns. The purpose was to allow quantification of potential rockfalls, and determine appropriate rockbolt lengths and spacings. The simple discrete fracture network (DFN) program used measured or estimated statistical distributions of joint parameters to generate rock mass discontinuity patterns in any required two-dimensional section. The approach lends itself to a probabilistic analysis, and to use data determined quantitatively from the DFNs in the evaluation of risk. The development philosophy and application of the method will be described in the paper, supported by descriptions of several cases of practical engineering problems. Since a DFN does not represent the actual rock mass, but only one example of a ‘theoretical’ rock mass, multiple DFN representations need to be used to quantify engineering outputs.