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The occurrence of rockfalls is a prevalent geological hazard, especially in the Three Gorges Reservoir area of the Yangtze River. Analyzing the pre-rockfall evolution process of hazardous rock mass is crucial for stability assessment, risk monitoring, and evaluation. Generally, numerical analysis is conducted to study the rock stability and failure; however, it is primarily based on the two-dimensional calculation of typical cross-sections without considering the shape of the three-dimensional space of the hazardous rock mass, thus leading to distorted results. To address this issue, this paper proposes a methodological approach for the analysis of the stability conditions of a hazardous rock mass. The approach starts with field investigations and an Unmanned aerial vehicle (UAV) photogrammetric survey to gather data. These data are then used to construct a three-dimensional (3D) geological model of rock mass. Finally, a 3D numerical simulation is performed to analyse the potential failure processes of hazardous rock mass. In this study, we focused on the hazardous Diaozui rock mass of the Qutang Gorge in the Three Gorges Reservoir area (China). We constructed a 3D geological model of the rock mass based on the data from the field survey and UAV photogrammetric survey. Using this 3D geological model, we established a 3D numerical analysis model to assess the rockfall hazard. By utilizing the Strength reduction method (SRM) and simulating the collapse process of the hazardous rock mass, we analyzed the instability mechanism and failure evolution process of the Hazardous Diaozui rock mass. The results illustrated the potential failure mode, the key-oriented wedges of the rock mass, and the potential critical failure point for the hazardous rock mass. These findings provide valuable insights for stability assessment, risk monitoring, and evaluation of the hazardous rock mass in the Three Gorges Reservoir area. [ABSTRACT FROM AUTHOR]

Ischia (Southern Italy) is a volcanic island of the Phlegrean Volcanic District that was historically affected by multiple geological hazards, including floodings, landslides, rockfalls, and earthquakes. In this study, rockfall stability is analysed with an integrated approach aimed at investigating the rockfall source, the propagation, and the deposition areas. The case study is represented by two outcrops over a 400-m-wide cliff made of Green Tuff and located on the western area of Mt. Epomeo. They are respectively located at 280 and 420 m a.s.l., just uphill the village of Frassitelli, Forio d’Ischia, which is an area of high residential, tourist, and agricultural importance. We analysed the fracture systems of the tuff cliff to compute the kinematic analysis of the potential failure mechanisms and to perform numerical simulations of rockfall scenarios. Successively, numerical simulations of rockfall scenarios were computed based on the acquired structural information. This allowed us to identify the most hazardous scenarios based on the rock trajectories and the percentage of rock blocks affecting the urban area. The influence of the rock shape and volume on the rockfall trajectories was analysed. In the most likely scenarios, we observed that 15–25% of the rock blocks bypass the geomorphological barriers and reach the urban area, with kinetic energy values spanning between 102 and 104 kJ. Such detailed rockfall hazard analysis allowed the definition of the mitigation interventions necessary for the protection of the nearby residential area. [ABSTRACT FROM AUTHOR]

The present study is aimed at analyzing the rockfall phenomena involving a carbonate rock scarp in San Donato di Ninea village (Calabria, south Italy), where some buildings and a portion of a road are exposed to a high hazard condition. The geomechanical investigations of the rock scarp were performed through a multi-approach based on in-field investigations, geophysical surveys, and high resolution of images acquired by a drone. The achieved data allowed to assess the quality of the rock mass and the susceptibility of rock slope to failure through the Rock Mass Rating and the Slope Mass Rating classifications, respectively. The obtained results showed slope conditions ranging between unstable and completely unstable. Geophysical surveys allowed to investigate the subsurface material and showed a high jointing rock mass in the shallower portion. In order to acquire the potential change in geomechanical features on the whole escarpment rock, high-resolution images were acquired by a drone. Thus, a 3D dense point cloud model was reconstructed in a setting of high accuracy based on 55 million of points with a density of 748.85 points for m2. The 3D model was imported into CloudCompare software to extract the geological planes through FACETS plugin, which allowed to recognize the jointing sets on the whole surface of rock escarpment. The digital data were compared with the ones collected by scanline method in order to verify their soundness, and further detailed digital investigations were carried out on human inaccessible areas to examine the corresponding fracturing degree. [ABSTRACT FROM AUTHOR]

The objective of this research was to prepare a rockfall susceptibility map. Explorations were conducted in the Dubračina River basin (Croatia). The input data included a geological map, an orthophoto and a 1-m digital terrain model (DTM). After a talus inventory was prepared, the seed cell concept was applied to define the rockfall source areas. The contributing factors (predictors) of rockfalls were evaluated by the chi-squared test. The analysis confirmed the following predictors: CORINE land cover, lithology, slope, aspect, distance from a spring, distance from a road, distance from a fault, distance from a stream, and distance from the rock-soil geological boundary. A matrix pairwise comparison of the predictor ratings was used to define the most significant contributing factors. The predictors that affected the susceptibility map in the share of 86.3% were the slope (61.6%), lithology (13.4%), CORINE land cover (6.2%), and distance from the rock-soil geological boundary (5.1%). Two susceptibility maps were prepared: one using all nine contributing factors and another using the four most significant factors. The analysis showed that both maps were good, with the same areas under the receiver operating characteristic (ROC) curves. The map prepared with only four contributing factors can be considered a better map due to its more precise spatial definition of critical areas. It can be concluded that geological map, 1-m DTM and orthophoto provide enough data to prepare reliable rockfall susceptibility map. The application of the bivariate statistical zonation method called the "frequency ratio method" was proven to be successful. This research demonstrates that the application of the seed cell concept can be useful to speed up the process of rockfall source area detections in large research regions. [ABSTRACT FROM AUTHOR]

Recent advances in remote sensing techniques and computer algorithms allow accurate, abundant, and high-resolution geometric information retrieval for rock mass characterization from 3D point clouds. The automatic application of the extracted information for local scale rockfall susceptibility assessment, where discontinuities characteristics play a major role in rocky slope stability, requires step by step logical procedures. This paper presents a novel methodology to use the extracted discontinuity set characteristics for a local scale rockfall susceptibility assessment, tailored for Uncrewed Aerial Vehicle (UAV) data acquisition. The method consists of 4 steps: (i) 3D slope model reconstruction using UAV digital photogrammetry, (ii) automatic characterization of discontinuity sets, (iii) slope stability analysis, and (iv) susceptibility assessment using a new Rockfall Susceptibility Index. The proposed method was applied to a road cut rocky slope in a mountainous area of the Samaria National Park, in Crete Island, Greece. Visual validation indicates that the areas of higher and moderate rockfall susceptibility on the 3D model of the rocky slope are adjacent to rockfall source areas marked by the presence of fallen blocks on the foot of the slope. The proposed methodological workflow presents novelties related to the use of point clouds for the estimation of the Rock Quality Designation (RQD) index, the visualization of discontinuity set spacing, the evaluation of the persistence and the Slope Mass Rating (SMR) index, as well as the incorporation of the persistence of overhangs into the rockfall susceptibility assessment and visualization. [ABSTRACT FROM AUTHOR]

Rock block characteristics are the controlling factors that define the potential rockfall volume, associated hazard and design of preventive practices. The present study defines a methodology to demonstrate the impact of block characteristics on rockfall hazard and its implications on the design of mitigative measures by analysing a recurring rockfall site along a critical highway corridor in NW Himalaya, India. The field data were quantitatively characterised for statistical distributions of size and volume of in situ as well as rockfall blocks. Possible block failures and rockfall initiation zones were predicted using modified kinematic analysis and distinct element method. The size and volume distributions as well as shapes were simulated against these predicted initiation zones to determine the cumulative impact of block characteristics on rockfall hazard by analysing the block kinetics and trajectories. It is found that the block initiation zones majorly govern the relative bounce height, kinetic energy, run-out distance and impact down the slope respective of block sizes and associated mass coupled with slope geometry. However, the effect of block shapes is observed to be minor compared to the blocks greater than a particular size range. Therefore, the design of rockfall protection such as barrier can be more effective when considering the kinetic energies of such block size range assisted by initiation zones. This study proposed that the knowledge of block size frequencies and rockfall initiation zones could provide a rational threshold for which a protection strategy can be designed and optimised to prevent rockfall hazard along the Himalayan highway corridors. [ABSTRACT FROM AUTHOR]

The runout behavior of rockfall is mostly determined by the terrain and its mechanical parameters. The two factors can be significantly changed in a short period of time due to rockfall deposits in high-frequency rockfall regions. In this paper, a self-evolution process of rockfall from the Hongshiyan post-earthquake rock slope is observed and analyzed. This self-evolution process of the rockfall is the consequence of the re-occurrences of a large number of rockfall events in a short period of time, which lead to an increase in the elevation, slope angle, and hardness of the terrain, and aggravate further the severity of subsequent rockfall disasters. In order to analyze the self-evolution process, numerical simulations based on a probabilistic model were carried out on eight different conditions to analyze the interaction between the rockfall and different ground surface. The corresponding rockfall hazard was then analyzed according to a quantitative assessment method. The statistics of the average class (AC) and mitigation index (MI) of the rockfall were proposed to quantify the rockfall characteristics in different conditions. The effectiveness of structural and non-structural rockfall protection measures in high-frequency rockfall areas was discussed. An interim non-structural measure that addresses the self-evolution of rockfall is proposed to improve the mitigation efficiency, which can also reduce the maintenance cost. [ABSTRACT FROM AUTHOR]

The winding Dasha River section of the Central Cross Island Highway in Taiwan is 9.44 km long. More than 20% of its length has been rerouted in the past six decades due to landslide-induced maintenance problems. To investigate the influence of geological conditions on the maintenance of this mountainous road section, this study establishes inventories of highway alignments and nearby landslides based on interpretations of multi-temporal aerial photos and highway maintenance records. Types of landslide and topographic features are verified through field investigation, and the engineering characteristics of rock masses are evaluated using the Q-method semi-quantitatively. The results reveal that three sections with rerouting of road or structural modification are located near the undercut slopes of the Dasha River and the boundaries of strata where water erosion and scouring are active and considerable gullies develop. Various metamorphic strata with intricate folds are formed by orogenic deformation and metamorphism under the influence of weathering, such as water erosion and scouring; these evolve into meanders and steep slopes. Gullies develop along the boundaries of strata with distinct lithology, where the engineering characteristics of rock masses vary markedly, disturbing the stability of nearby slopes and hindering the maintenance of the mountain road for long periods. Rerouting the highway and the use of a tunnel instead of the slope-cut-in halfway road effectively mitigate the influence of landslides near meanders where water erosion and scouring are significant. A gallery tunnel effectively mitigates rock fall. However, a gallery tunnel must be constructed without causing overcut-induced slope instability. [ABSTRACT FROM AUTHOR]

The Yumenkou tunnel is located on the left bank of the Yellow River on the border between Shanxi and Shaanxi provinces, China. It is connected to the Longmen Yellow River Bridge of the Menghua railway. Many unstable rock masses have developed on the cliff above the tunnel entrance, threatening the construction and operation of the tunnel and the bridge. Based on a high-precision three-dimensional (3D) digital terrain model obtained by unmanned air vehicle (UAV) photogrammetry, information of the structural surface which controls the stability of the rock mass in the study area was obtained by manual identification and extraction. We combined the UAV imaging with field survey data to obtain the spatial distribution, shape, scale, and potential failure modes of the unstable rock masses. A 3D numerical model of the unstable rock mass and surface morphology was constructed using a 3D discrete element method. The 3D path and impact energy of the moving unstable rock mass were analyzed. Based on the lithology, topography, structural surface, and other factors, three types of potential rock failure modes were identified in the study area: sliding, toppling, and falling. Differential weathering and the structure plane and stress-unloading cracks are two main factors affecting the stability of the unstable rock mass. According to the result of 3D discrete element method, once the unstable rock masses fail, about 50% of which might hit the portal of the tunnel, and the maximum rebound height at the portal would be about 1.2 m. To prevent such catastrophic failure, active protective net was recommend at each unstable rock zone, and retaining wall with a height of 5 m behind the portal. The results of this study confirm the effectiveness of a UAV photogrammetry-based method for reliable and cost-effective engineering geological surveying of unstable rock mass in complex terrain. [ABSTRACT FROM AUTHOR]

Regional geological mapping commonly records the dip and dip direction of dominant layering such as bedding and foliation but not the orientation of joints. It is common for joints to form an orthogonal pattern relative to the dominant layering. In that case, the three-dimensional possibilities can be extrapolated allowing inferences to be made about kinematically feasible structural failure mechanisms. The resulting planar sliding, wedge sliding and toppling kinematic assessment can be integrated on a stereograph. The analysis of extrapolated joint sets can be conducted in the initial desk-top stage of a site investigation. The method is demonstrated using field data from Devonian sandstones in eastern Victoria, Australia. The sandstones have joint sets and partings on axial cleavage orthogonal to bedding. The range of potential structural failure mechanisms is extrapolated from the known bedding orientation and slope face direction. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for estimating rockfall threats in carbonate rock cuts along railways in Croatia. The assessment is based on the Rockfall Hazard Rating System (RHRS). In general, the RHRS versions developed for Tennessee and Colorado are combined and modified to comply with Croatian carbonate rock mass properties, specific geological environments and values measured in the investigation area. The modifications are related to the classification parameters and corresponding adjustments of their classes. The exponential scoring of parameter classes is retained, but the calculation of final rockfall threat classes is modified. The proposed methodology is developed and applied to 366 cut segments along railways with a total length of 74.888 km. All rock cuts are located in the Dinaric karst area of Croatia, where carbonate rocks are locally susceptible to rockfalls, which mostly include sliding, toppling and ravelling. Rockfall threat is calculated for each cut segment with 15 different scoring models. The optimal scoring model is chosen according to the verification results. The verification is based on three different verification parameters: preliminary rockfall threat assessment, rockfall scars and cut stability, which are defined by the Regional Maintenance Administration of Croatian Railways. An ordinal logistic regression is performed to determine the threshold values for each rockfall threat class. The established methodology is used to detect the most vulnerable railway sections, which are selected for detailed inspection and reclamation. The research also enables a proactive approach of rockfall management along linear infrastructure in Croatia but also worldwide in similar geological environments. [ABSTRACT FROM AUTHOR]

Design block size is of vital importance for rockfall countermeasure design. According to the Austrian normative document ONR 24810, the design block is specified as fractile (V95-V98) of the block size distribution depending on rockfall frequency. For rock formations, which form very large rockfall blocks (> 10 m3), the use of fractiles V95–V98 appears too high with regard to economically justifiable protective measures. The paper deals with the determination of design blocks for the Dachstein Formation on the basis of data from three Austrian test regions. The formation's bedded limestone represents a key rock of the eastern part of the Northern Calcareous Alps and is very common along some major transport routes. A range of design blocks is derived from a synopsis of block size distributions, magnitude-frequency relations, and considerations about the rockfall barriers' service life. In the process, the knowledge of the return period of the determinated design block is considered more important than the overall rockfall frequency. Analyzing available rockfall event data and block size distributions, it is possible to identify a return period of 21–26 years for a rockfall event ≥ 1 m3/1000 m route section. Thus, such events are rare. Events that affect the V97–V100 fractiles of the block size distribution are even rarer; they yield very large design block volumes, which show return periods > 100 years. For the bedded Dachstein limestone of the test areas, the application of the fractiles V95–V96 (0.15–2.25 m3) is useful for adapting the return period of the design block to the working life of the rock fall barrier (25–50 years). [ABSTRACT FROM AUTHOR]

This study presents the results of a more than 10-year-long field investigation and remote sensing monitoring campaign of a highly active deep-seated rock slide located in a glacial to periglacial environment (Bliggspitze, Tyrol, Austria). Data concerning (i) the terrain surface displacements based on imagery (webcam time-lapse, ortho-images) and both terrestrial and airborne laser scanning, and (ii) the geological-structural and geomorphological situation were analysed to develop a geological-geometrical model of the rock slide and to study the temporally variable activity behaviour and the formation of individual rock slide slabs. Results clearly show that at least seven rock slide slabs were formed at different times and under different slope stability conditions. Some of these rock slide slabs were displaced at slow to moderate velocities and reached scarp offsets of several tens of metres, whereas other, shallower slabs collapsed and formed extremely rapid rock falls and avalanches. Generally, the rock slide is affected by rock mass cataclasis, fracturing and loosening, which in turn cause extensive mass loss accompanied by debris accumulation at lower parts of the slope. The cause for the development of the Bliggspitze rock slide is poorly understood. However, there are clear indications that permafrost degradation and/or glacial retreat, particularly at the foot of the slide, during the recent decades may have adversely affected the slope stability situation. [ABSTRACT FROM AUTHOR]

The Wudongde Hydropower Station is constructed in layered strata that typically have steep dip angles. These features, together with the folds and faults that have developed in the strata, directly threaten the stability of the underground powerhouse. In this work, the behavior of the surrounding rocks under the original support measures is detailed in terms of rock mass deformation, anchor bolt stress, and extent of the excavation-disturbed zone, as obtained from safety monitoring and field testing. The characteristics of deformation and cracking of the surrounding rocks were also interpreted. To enhance rock mass stability, the support design and construction process were optimized and the positions liable to cracking treated. The efficiency of suggested scheme is verified by subsequent safety monitoring data and field testing. Then, a transversely-isotropic elastoplastic constitutive model for the layered rock masses was established. Numerical simulations are performed during the construction process to provide reference for decision making. The calculated deformations are in good agreement with the monitored values and they tended to be more stable. The plastic zones of the surrounding rocks fall within the range controllable using cables. Thus, the proposed measures are necessary and ensure sufficient stability. Finally, the mechanisms for the deformation and cracking of the surrounding rocks during the construction process are discussed. The work described aims to deepen our understanding of the mechanical properties of layered rock masses with steep dip angles and to improve the design philosophy. [ABSTRACT FROM AUTHOR]

Tower-shaped rock masses are particularly susceptible to failure, via fracture and disintegration, due to their inherently large height-to-diameter ratio. A rockfall event at the Zengziyan Cliff, in Chongqing, China, was selected for a case study. Based on video footage, the movement characteristics of the initial failure processes were analyzed in three movement stages: initiation, acceleration and deceleration. The failure process began at the bottom of the tower-shaped unstable rock mass and manifested itself in the form of fissure extension followed eventually by disintegration. The acceleration curve presented a continuous negative fluctuation associated with buffering in the deceleration stage. At the same time, the movement characteristic curves at different measurement points displayed significant time-dependent differences, proving that cracking, collisions and disintegration occur in the failed rock mass during the initial failure process. The results of this analysis provide a reference for the early identification of similar rockfalls and for analysis of their mechanisms. [ABSTRACT FROM AUTHOR]

This study addresses the instability problem of typical slopes in the engineering constructions of bridges and tunnels in Southwestern China by combining the results of detailed field monitoring, geological and geometrical investigation, and numerical simulations and then proposes comprehensive protection measures. The study area is a vital part of the Chengdu–Lanzhou high-speed railway in Sichuan Province, located in the 5·12 Wenchuan's meizoseismic area. The slope stability was analysed based on the data collected by field monitoring. The results indicated that the slope toe was stable under a natural state, while a large deformation was observed occasionally owing to tunnel blasting and excavation. Subsequently, a digital binocular camera installed on a fixed-wing unmanned aerial vehicle was used to identify unstable rockmass. By analysing the slope and the dip direction angles, three potential paths of rockfall hazard were selected for further studies. A retaining wall and a soft protecting net were installed along the slope to intercept potential debris flow and possible falling rocks above the tunnel portal, respectively. A Mohr–Coulomb model was built using universal distinct element code to identify the rockfall initiation position. Overall, the field monitoring results were in good agreement with those obtained by numerical simulations. Moreover, the Rocscience Rocfall program was used to calculate the bounce height and the total kinetic energy of falling rocks. Finally, mitigation measures for the potential landslide, rockfall, and mudslide hazard were proposed and adopted in practical engineering applications, and aimed to provide a useful reference for similar engineering practices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Rockfalls pose serious threats to human beings, structures, and lifelines. In the present research, a model was developed to predict the possibility of seismic rockfalls on a regional scale. For this purpose, three models including logistic regression (LR), a multilayer perceptron artificial neural network (MLP), and a radial basis function artificial neural network (RBF) were employed. Bivariate logistic regression is a multivariable statistical method that provides a mathematical model using independent variables to predict the occurrence probability of a given phenomenon at a certain location. Although artificial networks of RBF and MLP are pretty similar, there are some structural differences in the components between these two neural networks. The earthquake of Changureh-Avaj in 2002 was used as a basis and benchmark for the model presented in this work. The sustainable zones predicted by LR, MLP, and RBF methods were compared with a database (distribution map) of seismic rockfalls. The results showed good overlap between RBF-predicted rockfall susceptibility zones and database (distribution map) of seismic rockfalls. Besides, in order to evaluate the statistical results of LR, MLP, and RBF models, the verification parameters with high accuracy such as density ratio (Dr), quality sum (Qs), and Receiver Operating Characteristic Curve (ROC) were used. By analyzing the susceptibility maps and considering the Qs index obtained by LR (2.94) and MLP (3.482), and RBF (4.344), it could be observed that the Qs of RBF were higher than that of LR and MLP. Moreover, based on the obtained value of AUC from LR (0.859), MLP (0.910), and RBF methods (0.956), it is seen that the RBF method provided a higher accuracy in predicting the probability of rockfalls occurrence caused by the earthquake of Changureh-Avaj in 2002 compared to LR and MLP methods. [ABSTRACT FROM AUTHOR]

Rock fall hazard management typically requires efficient allocation of available resources for detailed hazard assessment and control. In mountainous terrain, remoteness and difficult access pose a challenge for resource allocation decision-making. In this paper, we evaluate a systematic approach for decision-making based on topographic susceptibility and efficient three-dimensional trajectory modelling. The approach relies on the availability of detailed digital elevation models, a strategy which is now considered to be the state of practice. In this study, it is assumed that geologic and rock mass quality information, as well as rock fall occurrence records, are not available in the necessary detail across the area of study for them to be used in rock fall hazard assessments. The approach is illustrated with a case study along a section of railway within the Canadian Cordillera. The advantages and limitations of the approach are discussed, as well as some key considerations for its application. [ABSTRACT FROM AUTHOR]

Conglomeratic rocks are composed of macro-particles (varying in size from gravels to cobbles and boulders with diameter greater than 2 mm) bonded by fine-grained cement particles with diameters of < 2 mm. Determination of strength and deformability of such materials in the laboratory is challenging due to sampling and testing constraints induced by the strength and stiffness contrast of the particles and the cement matrix. Alternatively, the mechanics of such materials has been studied by laboratory testing on a synthetic conglomerate composed of steel spheres and Portland cement. The physical modeling and testing was supplemented by numerical simulations in PFC3D by preparation and testing of equivalent numerical models. This paper presents the results of numerical investigations conducted on conglomerates with the objective of finding the effect of particle size distribution, scale effects and the sensitivity of variable mechanical parameters of clasts and cement. Two different clast particles were considered, namely sandstone and granite, both with Hertzian contacts in addition to steel particles. For each clast type, the following bed matrices were modeled to glue the clasts by deriving necessary micro-mechanical parameters from published literature; Portland cement, argillaceous cement and arrenaceous (quartzitic) cement. The mechanical responses of the numerical conglomerates were examined in uniaxial, triaxial and Brazilian tensile testing. Macroscopic behavior of each combination of conglomerate was then analyzed. The results show that particle size distribution affects both the mechanical response and damage pattern in the specimen, while scale, i.e. the effect of specimen size, keeping the micro-structure the same, was found to influence the strength and elastic response of the conglomerates similar to other natural rocks. The properties of clast and cement were also found to influence mechanical response of conglomerates in numerical simulation. The peak strength and the stiffness of the conglomerate increases with the increase of the stiffness and the strength of the cement matrix in uniaxial or close to uniaxial stress states, while negligible dependence on the stiffness and strength of the clast material. In contrast, the mechanical properties of clast materials were found to increase the strength and stiffness of the conglomerate in triaxial stress states, while there was negligible dependence on the strength and stiffness of the cement matrix. [ABSTRACT FROM AUTHOR]

The prediction of the average size of fragments in blasted rock piles produced after blasting in aggregate quarries is essential for decresing the cost of crushing and secondary breaking. There are several conventional and advanced processes to estimate the size of blasted rocks. Among these, the empirical prediction of the expected fragmentation in most cases is carried out by Kuznetsov's equation (Sov Min Sci 9:144–148, 1973), modified by Lilly (1986) and Cunningham (1987). The present research focuses on the effect of the engineering geological factors and blasting process on the blasted fragments using a more powerful, advanced computational tool, an artificial neural network. In particular, the blast database consists of the blastability index of limestone on the pit face, the quantities of the explosives and of the blasted rock pile, assessing the interaction of these parameters on the blasted rocks. The data were collected from two aggregate quarries, Drymos and Tagarades, near Thessaloniki, in the Central Macedonia region of Greece. This approach indicates significant performance stability, providing the fragmentation size with high accuracy. [ABSTRACT FROM AUTHOR]

Large, deep open-pit mining projects lead to rockfall, which becomes an engineering hazard second only to slope stability. The V shaped gully (V-gully) method introduced here was shown to have a significant effect on preventing rockfall through reduction of kinetic energy and rainfall discharge. The method, where a gravel cushion was laid on the V-gully surface, was applied in a typical open-pit mine. A drain dyke should be set at the bottom of the V-gully to discharge rainfall effectively. The slope stability analysis under different drainage rates was calculated by Modified Sarma (MSARMA) software. Slope stability, engineering activities and weathering condition of slope were taken into account to identify the rockfall prone areas. RocFall numerical software was used to calculate the effect of various angle V-gullies on the movements of various rockfall. A striking reduction in kinetic energy of rockfall was achieved, and the effects of V-gully protective measures were studied. Then, a system for controlling rockfall effectively and economically was designed for a particular slope according to the field situation. The effectiveness and reasonableness of design were evaluated through numerical simulations and field testing. This paper provides a theoretical and practical basis for a novel rockfall prevention technique on the high-steep slopes in similar engineering projects. [ABSTRACT FROM AUTHOR]

The Dujiangyan-Wenchuan highway serves as a vital passage to and from the region severely damaged by the 5.12 Wenchuan Earthquake in China. Chediguan Bridge is located on the highway and spans the Minjiang River. During the earthquake, the bridge was severely destroyed by rockfalls. Although the bridge was subsequently rebuilt and opened to traffic on May 12, 2009, it was destroyed again on July 25, 2009 by rock avalanches that had been located perilously high on the right bank of the Minjiang River, and caused deaths, casualties, and roads being cut off. A subsequent investigation revealed multiple perilous rocky areas on the massif along the Minjiang river bank, indicating an extremely high risk of another rockfall hazard, which could, again, lead to damage to the bridge and a further disastrous outcome. To mitigate the rockfall hazard to the bridge, a new flexible, energy-dissipating crashworthy device for bridge piers is developed to withstand the impact of rockfall. Numerical simulations using nonlinear finite element analysis was carried out to simulate the rockfall impact process on bridge piers. The following influencing factors during the impact process were taken into account: material nonlinearity, geometric nonlinearity, as well as contact nonlinearity. The results show that the new protective structure of bridge piers can effectively buffer rockfall impacts and significantly improve the anti-impact capability of the bridge piers. [ABSTRACT FROM AUTHOR]

Collision-induced fragments from large volume isolated rock block collapsed from cliffs with heights of hundreds of meters could cause greater distal reaches via superimposing additional velocities on the frontal smaller fragments at the impact zone. These fragments may pose significant threats to distant infrastructure, life, and property due to their extremely high velocities and disastrously long runouts. To reveal the collision fragmentation mechanism on the evolution of higher velocities fragments and predict the distal reach of the frontal smaller ones, a two-dimensional block-terrain impact model of an intense brittle rock block colliding onto a rigid plane is proposed. Furthermore, the well-documented experiments on collision fragmentation of brittle chalk were used to verify the derived mathematical equations of the model. The results indicated that the calculated results can match experimental data well. The proposed model can provide meaningful insights into the kinetics of fragmental rockfalls and enable predictions of the possible distal reaches of explosive fragments, which are crucial for hazard zoning and mitigation design. [ABSTRACT FROM AUTHOR]

Using laser scanner data, an exhaustive rockfall database has been established for a rockwall located near the town of Grenoble (France). The study site is a long double cliff, on the eastern border of the Chartreuse Massif. The two cliffs consist respectively of thinly bedded and massive limestone, which show different structures, morphologies and rockfall activities. The 3D point clouds obtained by laser scanner allow to detect and model the fallen compartments in 3D. Information about cliff surface, and localization, dimensions, failure mechanism for each compartment were obtained and analyzed in order to characterize the morphological evolutions of the cliffs. It appears that the morphology and the slope of the lower cliff is related to fracturing and torrential erosion which occurs in the marls below the cliff, showing a rockfall frequency 22 times higher than for the upper cliff. These results show that the erosion process in the lower cliff is in a transient state, whereas it could be in a steady state in the upper cliff. Rockfalls have been dated by a near-continuous photographic survey (1 photo each 10 mn) and a monthly survey during 2.5 years. The analysis of the two data bases shows that the rockfall frequency is 7 times higher during freeze-thaw episodes than without meteorological event, and 4.5 times higher during rainfall episodes. Moreover, it becomes 26 times higher when the mean rainfall intensity is higher than 5 mm/h. Based on these results, a 3-level hazard scale has been proposed for hazard prediction. [ABSTRACT FROM AUTHOR]

Combining the results of detailed field investigation, laboratory tests, and numerical simulations, this paper studies the rockfall problem above a tunnel portal. The mechanism of potential rock instability was analyzed, and model tests were conducted based on geological conditions and described in detail, so as to study the restitution coefficients used in programs simulating rockfall trajectory. Improvements in the tests were made in terms of experimental techniques and creative similar materials. A newly developed test bench was built by steel frames and can be assembled or disassembled at will according to requirement of model size. An innovative block-release device was adopted and controlled by computer to change the release position of block. During the model construction, the slope and blocks were fabricated with similar materials developed through quantities of mixing proportion tests. Then experiments were conducted with varied shape, mass, and release height of blocks to clarify their effect on restitution coefficients. Results indicate that restitution coefficients are apparently related to these factors and their values decrease when block mass and releasing height increase. Restitution coefficients of the wedge block are larger than those of a sphere or cuboid block. Subsequently, numerical simulations adopting the calibrated parameters were performed, and the velocities, bounce heights, and kinetic energies of rockfall along the slope profiles were obtained. Based on the research, this paper provides a useful reference for practical remediation design. [ABSTRACT FROM AUTHOR]

The stability of rock slopes is an important area of interest in civil and mining engineering. This study investigated rockfall occurring around the Gökgöl 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. [ABSTRACT FROM AUTHOR]

The present work illustrates the monitoring system of the Ingelsberg slope (Bad Hofgastein, Austria), which hosts one of the most dangerous landslides in the Salzburg Land. It is a rock fall, which can be considered as representative of landslides commonly occurring in the Alpine area. During the monitoring campaign (March 2013-July 2014), a rock fall occurred at the end of April, 2013 that involved 20-40 m of rocks. The comparison of surface measurements (by Ground-Based Interferometric Synthetic Aperture Radar-GB-InSAR) with measurements in depth (by extensometers) allowed the understanding of the failure process of the rock mass. Data are discussed taking into account meteorological conditions antecedent to the landslide triggering, indicating that factors such as rapid snow melting (added to first spring rainfall events) and rock thermal dilatation are very important in slopes located far below the permafrost line. [ABSTRACT FROM AUTHOR]

This paper deals with a quantitative risk analysis, performed using the rockfall risk management (RO.MA.) method, for a road affected by rockfalls. This approach allows evaluating the rockfall risk, also considering existing protection devices. Rockfall hazard and risk were assessed for an important and very busy road stretch linking Positano to Amalfi in the Campania region of southern Italy. An estimate of the rockfall return periods for assigned volume classes was obtained using the magnitude-frequency curves (MFCs) computed through the analysis of a rockfall inventory covering a time span from 1996 to 2008. For rockfall volumes of 0.1, 1.0, and 10 m, using a 2D trajectory simulating code, the involved kinetic energies and run-out distances of boulders that may hit the road were calculated. The risk, expressed as the annual probability of a fatal accident for the three rockfall hazard scenarios has been evaluated both without and with protection devices, respectively. The total final risk is given by the sum of partial risks related to the three scenarios. The analysis showed that regardless of whether there are any rockfall protection devices, the total risk remains almost constant. This is due to the wide spread of slopes protected with inadequate restraining metallic nets characterized by decreasing catching capacities, as possible rockfall magnitude increases. The individual risk is not acceptable, and some actions are requested in order to lower it. [ABSTRACT FROM AUTHOR]

Probabilistic approaches are widely adopted for the modeling of rockfall trajectories, but are not widely discussed in the literature. This paper aims to help fill this gap by reviewing probabilistic models of rockfall trajectories, while providing some perspectives for future study. We first make it clear that, from a theoretical point of view, the probabilistic approach is necessitated by both the ontic (inherent) uncertainty associated with rockfalls and the epistemic (information) uncertainty associated with numerical modeling. The review suggests that there may be the potential to improve the probabilistic modeling of rockfall trajectories in various aspects, including the systematic probabilistic modeling criterion, the random sampling approaches employed for probabilistic variables, the probabilistic modeling of rock shape, and the probabilistic prediction of rockfall intensity. However, there are still some open questions regarding the promotion of probabilistic modeling in practice. It is not clear whether probabilistically treating all of the variables of rockfall trajectory model with reasoned distributions will lead to significantly improved results, or whether the improvements will be great enough (given the difficulties and costs involved) that it is worth quantifying all of the uncertainties involved in rockfall trajectory modeling. The answers to these questions can be found in the practice of probabilistic modeling itself. [ABSTRACT FROM AUTHOR]

The Serra do Mar mountain range is a fault scarp with steep slopes that are often affected by shallow landslides triggered by extreme rainfall. Most of these events result in casualties and economic and environmental damage, especially in areas close to urban centers, major roadways and agricultural areas. The goal of this study was to evaluate the susceptibility to shallow landslides in the Serra do Mar, specifically within a drainage basin affected by such an event in January of 1985. For this purpose, the mathematical modeling technique of SINMAP was used by introducing the topographic values from a digital terrain model as well as geotechnical and hydrological values from previous studies performed in the Serra do Mar. In all, 32 susceptibility scenarios were generated, and three were analyzed for this study. These scenarios were validated using landslide scar maps produced using orthophotography; this technique was also used to analyze the functions of morphological parameters (e.g., slope angle, curvature and hypsometric features). The basin was classified as unstable, with landscape rates above 70 % for all three of the scenarios chosen. A higher landscape frequency was expected on straight slopes with angles between 30° and 50° under unsaturated soil conditions, as evidenced by low moisture rates, especially for N-S-facing slopes. The susceptibility maps generated using this model should prove useful for other critical parts of the Serra do Mar to understand better and, above all, predict these landslides, which annually cause significant damage in Brazil. [ABSTRACT FROM AUTHOR]

The transportation route between Chamoli and Badrinath in Uttarakhand is mainly a pilgrimage route to the famous Badrinath temple, at an elevation of ~3,100 m asl. It is estimated that some two to three million vehicles use this road annually, particularly between May and October. The Lesser and Higher Himalayan rocks exposed at 23 localities along the transportation corridor contain numerous joints. In view of their orientation, blocks of rock of varying sizes are susceptible to falling, endangering the vehicular traffic and the numerous village settlements along the route. In this study, kinematic rockfall hazard analysis was carried out for all the 23 localities where in situ rocks are observed. The results of the analyses were evaluated and the areas classified as of low, moderate, or high hazard. [ABSTRACT FROM AUTHOR]

The epicenters of the 2013 Lushan earthquake and the 2008 Wenchuan earthquake were both in the Longmen Mountains, in areas with similar geographical, geological, and geomorphological conditions. However, there are some differences between the landslides triggered by the two earthquakes. Correlations between the occurrence of landslides and geological parameters such as the distance from the seismogenic fault, seismic intensity, elevation, and lithology were analyzed with the aid of field investigations. Firstly, more landslides were triggered by each earthquake close to the seismogenic fault and in areas with higher seismic intensities, although there were also obvious differences between the landslides generated by the two earthquakes. Secondly, the earthquakes showed different correlations between the number of landslides and elevation, and this difference was closely related to the effects of seismic amplification and peak ground acceleration. Nevertheless, the effect of seismic amplification during the Lushan earthquake was not significant at elevations of >2,000 m due to a reduction in earthquake magnitude at such elevations. Thirdly, there was no obvious correlation between the number of landslides and the age of the rock (young or old lithology) for each earthquake. Indeed, differences between the distributions of landslides across different lithologies were actually due to the coincidental clustering of young or old strata around the rupture zone of the seismogenic fault; these rock masses were extremely fractured and they underwent strong shaking. Finally, the author hopes that the results of the present research will aid further research into the landslides triggered by the two earthquakes. [ABSTRACT FROM AUTHOR]