Rockfall Hazard Research Articles

Quantitative assessment of rockfall hazard in post-landslide high rock slope through terrestrial laser scanning

Quantitative assessment of rockfall hazard in post-landslide high rock slope through terrestrial laser scanning

Rockfall Hazard Analysis Based on the Concept of Functional Safety with Application to the Highway Network in South Korea

Numerous rockfall incidents involving infrastructure damage and loss of life have been reported along roads in mountainous terrain. Previous studies have used quantitative risk assessment approaches to identify the level of rockfall risk. However, appropriate quantitative indicators that are able to describe time-varying risk have not yet been developed. This study aims to develop a rockfall risk mitigation method based on reliability concepts, to classify rockfall data, to model the probability of rockfall occurrence, and to estimate the magnitude of risk reduction through mitigation measures. A synthetic measure of rockfall risk is proposed, which allows to compare directly and quantitatively the rockfall risk for different cut slopes under unmitigated and mitigated conditions. The proposed methodology can estimate the risk reduction obtained using mitigation measures, such as introducing protections barriers, their periodic maintenance, and horizontal coverage ratio. This methodology was applied to 20 years of rockfall data collected by the Korea Expressway Corporation from 1215 artificial cut slopes along the highway network in South Korea. The rockfall frequency was analyzed based on the inventory data, and a rockfall hazard mitigation strategy was demonstrated using the suggested methodology for the case study. It was shown that appropriate mitigation strategies, based on number of protection barriers, interval of periodic maintenance, and horizontal coverage ratio, can be devised to reduce the risk of different artificial slopes below a target failure probability. The approach shown in this study can provide insights into ways of improving overall risk management to prevent losses by rockfall.

Geomechanical study and rock fall hazard analysis in the historical Centre of Forza d’Agrò (Messina - Italy)

The present study shows the result of a rock fall hazard evaluation of the area downstream the Norman Castle that overlooks Forza d’Agro (Messina Province - Italy). The study was aimed at evaluating the penetration capacity of a rockfall in the inhabited center, to evaluate the number of houses involved in the transit area of the boulders. On the basis of the data obtained, a hazard assessment was developed that took into account not only the type and magnitude of the landslide phenomenon, but also the probability of occurrence of the event or its return time.

Rockfall hazard assessment of the Monte Gallo Oriented Nature Reserve area (Southern Italy)

The Monte Gallo area is a carbonate relief that develops a significant nature reserve and highly attracts tourism to the urbanized area of the City of Palermo (Southern Italy). The slopes are affected by several rockfall events, which have also caused death, injuries, material damage, and a strong social and economic impact. Here, a detailed geological and geotechnical study to assess the rockfall hazard relating to two sectors of the mount has been carried out. The hazard assessment at the slope scale was performed based on geological, geomorphological, geomechanical, and seismic analysis. Using both analytical and empirical methods and by means of different software, the reconstruction of the propagation areas for the eastern sector of the Mount was possible. Results were used to better understand the overall structure, characterize the rockfall source areas’ kinematics, and recognize the basic failure mechanisms. The obtained runout areas were compared with each other and with those of previous studies conducted in a neighboring area, as well as with the corresponding hazard area maps of the official cartography, which is being updated. It is expected to be supplemented with maps derived from empirical models.

A Modern Approach in Analyzing and Designing of Rockfall Protection Measures: The City of Omiš Rockfall Protection Case Study

Extended abstractRockfalls are the most frequent and dangerous type of landslides, generating high economic and social damages in zones built in different types of rock mass. The high danger of rockfall occurrence mainly lies in high speed of the falling rock mass that is very difficult for any fast response in the protection of human lives, settlements and infrastructure. The main part of Adriatic coast of Croatia is built in the limestone rock mass and numerous cities and traffic infrastructure were built in a narrow coastal belt, just below steep slopes of limestone massifs [1]. Numerous cities (e.g. Rijeka, Omiš, Makarska, Dubrovnik) and small settlements, as well as hundreds of kilometres of roads, are exposed to rockfall threats and their consequences expressed in human lives and economic damage. Because of the nature of a rockfall occurrence, where relatively small rockfall volume can cause extremely high damages, there were numerous projects in rockfall protection along the Croatian part of Adriatic coast last years.One of the most comprehensive and by its volume the most important project in Croatia was the City of Omiš rockfall protection project conducted from 2006 to 2018 [2]. After the numerous rockfall occurrences that hit the City during its known history, the modern rockfall protection constructions and new technologies in rockfall analyses and protection designing enabled the development of the efficient rockfall protection systems. In this paper, we will describe the methods of field and remote sensing investigation of rock slopes, identification of rockfall sources, modelling and simulation of rockfall propagation, as well as the selection of protection measures and their positioning at the slopes above the central part of the City of Omiš. The carried out measures and estimation of their efficiency in reduction of rockfall hazard and risk in the central part of the City of Omiš will be described.

Application of Spatial Multi-Criteria Analysis (SMCA) to assess rockfall hazard and plan mitigation strategies along long infrastructures

Long infrastructures often cross areas with a high probability of landslides, causing eventually serious problems to the serviceability and compromising safety. The identification and prediction of hazardous zones are difficult, especially for what concerning rockfalls, as they can occur quickly and suddenly. In order to assess rockfall hazard, detailed data such as slope geometry, geotechnical and geomechanical properties of materials, drainage system pattern, etc. are needed. Even though thematic datasets are available and easily downloadable for the majority of the Italian territory, their scale is not adequate and ad-hoc input data must be gathered. An original multi-disciplinary procedure (GEO4) has been developed by the authors based on a mobile mapping system (ARCHITA) integrated with Airborne Lidar and ILI (In-Line Inspections), geomatics, geological models, geotechnical-geomechanical characterization and geomorphometric approach. A Spatial Multi-Criteria Analysis (SMCA) is then used to create a composed and spatially distributed index of landslide hazard based on normalized values of triggering factors. Such index is used to identify and classify the morphological unstable element along the infrastructure, supporting decision-makers in defining the most appropriate mitigation measures and planning their implementation in a clearer, more repeatable and more objective orientated-way. The presented method has been successfully applied so far to hundreds of km of railway lines in Italy.

Numerical Analysis of The Wire-Meshed Net Anchoraged

The rockfall hazard in areas such as mountainous regions, quarries and mines needs to be well managed. This is essential in order to avoid fatalities, damage to infrastructure and production losses. Preventing all rockfall events is almost impossible, but the installation of rockfall protection systems is a common and effective way to control the hazard. The installation of wire-meshed net anchored is a possible solution to prevent slippage of landslide of the surface layers. This paper will be focused on the study of numerical modeling, using finite element analysis software, ABAQUS, of double-twisted hexagonal wire-meshed net anchoraged which has been developed by the French-based company, GTS. The objective is to analyze several configurations and performances of wire-meshed nets, cables. As final result, we will comparing between the experiment and numerical modeling analysis.

Rock Fall Hazard Analysis for In-Pit Operations Potentially Impacting External Sensitive Areas

Controlling rockfall-related risks is a requirement for safe pit operations and primarily mitigated through adequate bench geometry design and implementation. This paper presents a method for rockfall hazard analysis for in-pit operations potentially impacting external sensible areas, adapted from natural rockfall hazard analyses. The method considers the natural susceptibility to rockfalls pre-mining, rockfalls originated from bench failures, and those initiated as flyrock. Rockfall trajectory models are used to estimate the potential for blocks reaching exposed elements. Natural susceptibility to rockfalls and trajectories are used as a baseline on which to evaluate the potential effects of open pit operations on the environment and perceptions of communities in the area. The method is illustrated for an open pit in steep terrain in the Peruvian Andes at a feasibility level of study. The paper illustrates the flexibility for including considerations of pre-mining rockfall impacts on the external elements of interest, and for developing rockfall mitigation strategies that consider rock block velocities, heights, energies and the spatial distribution of trajectories. The results highlight the importance of considering the three-dimensional effects of the terrain on block trajectories, and how such insights allow for increasing the efficiency of resources available for rockfall protection structures.

Geotechnical slope stability and rockfall debris related safety assessments of rock cuts adjacent to a rail track using aerial photogrammetry data analysis

Transportation infrastructure facilitates the accessibility and mobility of goods, people, and services through its vast network spanning across the USA. The departments of transportation (DOT) agencies face many challenges in monitoring and maintaining these infrastructure assets for continuing their service and operations, especially those located adjacent to slopes in rural and remote areas. Mobilizing and conducting traditional infrastructure inspections in those conditions can be laborious and time-consuming. Also, the unstable or highly weathered rock slopes pose significant rockfall hazards due to the moisture content, intrusion, and temperature changes, transpired over a period of time, causing weathering and rockfalls, ultimately resulting in debris accumulation. Recently, unmanned aerial vehicles (UAVs) in conjunction with close-range photogrammetry techniques are being researched and used ubiquitously for infrastructure monitoring applications in and around mountainous regions. In this study, a rock-cut located in a remote terrain where a rail track was passing through was aerially inspected and imaged for performing a comprehensive safety assessment and analysis to evaluate the stability of rock-cut and ways to assess rockfall safety zones and boundaries. A unique approach was developed by leveraging the aerial mapping and data compilation along with an immersive three-dimensional visualization of slopes for conducting stability analysis followed by the evaluation of rockfall debris zones adjacent to rail tracks. Successful assessments conducted in this study indicate that the methodologies will benefit the transportation agencies in effectively monitoring and managing transportation infrastructure adjacent to hilly terrains and ensure the maintenance of safe clearance zones needed to safeguard the public and property.

GPR‐MCS model of reliability analysis of key blocks and its engineering application

AbstractReasonable rock bolting schemes for potentially unstable blocks should be proposed and optimized in order to prevent rockfall hazard during tunnel construction. However, the reliability index of key block caused by uncertainty of geometric and mechanics parameters is not easy to be obtained by numerical simulation. Since the performance function of stability analysis of supporting key block is too complex, it is also difficult to calculate the reliability by using analytical and graphic methods rapidly. In this paper, the Gaussian process regression (GPR) model was established instead of the explicit function of key block. The safety factor of supporting key block calculated by UnWedge procedure was taken as the sample output of response model. With the GPR model coupling Monte Carlo Simulation (GPR‐MCS), the failure probability of key block could be predicted rapidly. The reliability of key block with different supporting schemes were analyzed, and the optimization of support parameters for key block was also carried out. It has direct meaning to prevention and control of dangerous key block during tunnel construction.

A Dynamic Strain-Rate-Dependent Contact Model and Its Application in Hongshiyan Landslide

An earthquake-induced landslide, mainly affected by seismic movement, is a frequent large-scale geological hazard in hydraulic engineering. This paper proposed a rate-dependent strain-softened micromechanical contact model and implemented it in discrete element method code, namely, PFC. Using the PFC-FLAC coupling scheme, the Hongshiyan earthquake landslide is analyzed as a case study. The influence of the strain rate, damping, and topographic effect is discussed. The results indicate that the rate-dependent micromechanical model can give a reasonable seismic-induced failure process compared with the in situ situation and provide a numerical technique for earthquake-induced landslide analysis and rockfall hazard prediction.

Rockfall analysis in the area of Kakia Skala, Greece

Because rockfalls cause significant hazard on human activities and infrastructure, the rockfall analysis is considered to be very important along roads and on other geotechnical works. Especially, in Greece owing to the complexity of geological structure, the tectonic characteristics, the climate and the high seismicity, this analysis is of great importance. This paper presents the topographical, geological, tectonic and seismic features and determines the Rock Mass Rating and Rockfall Hazard Rating System values of the tectonically disturbed limestones in the area of “Kakia Skala”, which is part of the “Patra–Athens–Thessaloniki–Evzoni (P.A.TH.E.)” motorway—one of the most major highways in Greece. For this reason, after geological and geomorphological investigations, bibliographic references and the characteristics of the road construction (tunnels, embankments, trenches, etc.), the most dangerous positions were identified (eight). Finally, the two most dangerous sites were selected for separate rockfall analysis. The RocFall software is used for the estimation of the unstable blocks trajectories and their kinematic characteristics. The appropriate support measure, with the right dimensions, is selected according to the kinetic energy of the falling rocks, and it is placed at the appropriate location.

Geologic hazards of the Ocoña river valley, Peru and the influence of small-scale mining

The Ocona River Valley, in the Arequipa Department in southern Peru, extends over 150 km from the Pacific coast to its headwaters in the Andes Mountains. While traditionally sparsely populated with farmers and crawfish fishermen, the valley has seen a large population growth in the last 20 years as small gold mines have developed. This change poses the opportunity to evaluate three research questions: How do geologic hazards and risks increase from mining activity? How does unplanned urban development affect risks? How do landforms restrict development and thereby increase risks? The combination of climate, topographic, and hydrologic conditions result in widespread hazards from debris flows, collapsible soils, erosion, rockfall, flooding, and liquefaction. We have developed maps of these hazards for three communities where mines have recently developed, Secocha, Alto Molino, and San Juan de Chorunga, and then we conducted a risk analysis for changing conditions, termed “Risk–Risk” analysis. Because of the lack of vegetation on mountain slopes, mining operations typically only affect rockfall hazards, mostly in the immediate vicinity of the mines and in the nearby runout zones. However, increased population and associated settlement infrastructure is constrained by steep slopes and regularly-flooded valleys, so residents live in fan and terrace areas with substantially increased risks from debris flows and collapsible soils and moderately increased risks from flooding and rockfall.

Impact of rock block characteristics on rockfall hazard and its implications for rockfall protection strategies along Himalayan highways: a case study

Impact of rock block characteristics on rockfall hazard and its implications for rockfall protection strategies along Himalayan highways: a case study

Roof fall hazard assessment with the use of artificial neural network

The paper presents the results of roof fall hazard analysis for the copper mines in Poland. At first, RMR and RFRI systems have been checked as a tool for roof fall hazard assessment. It was proved that rock mass deteriorates in time because of mining operation at the site, hence the roof fall phenomena analysis needs a new approach. In the next step of the analysis the key factors of roof deterioration were determined, and divided into four groups: geological, mining, technical and monitoring. It was demonstrated that only regular roof monitoring can ensure the proper rock fall hazard assessment. Subsequently, the artificial neural network was created and several dozen simulations were conducted. As a result, two dimensionless indices were developed. The first one shows predisposition of a part of the rock mass to destruction, dislocation and deformation - CRFP - Coefficient of Roof Fall – Predisposition and the second one represents predisposition and possibility of maintaining of the working - CRFM- Coefficient of Roof Fall - Maintenance. The research on roof fall details and the running workings’ roof observations allowed for categorization of the values of both indices, and providing that way the information about roof stability CRFP, and the information about necessary measures and solutions for the supervisory staff in regard of monitoring of the roof rocks CRFM. Both indices allow for a reliable roof fall hazard assessment by comprehensively combining information from monitoring, observations and investigations.

Factors Influencing the Coefficient of Restitution in Rockfall Impacts

AbstractAs an outcome of epigenetic reformation in rock slope, the rockfall hazard poses significant detriment to human activities and infrastructure. Among the related parameters including inciden...

GIS-Based Multi-Criteria Decision Analysis Approach (GIS-MCDA) for investigating mass movements’ hazard susceptibility along the first section of the Algerian North-South Highway

The North-South highway is a central axis of the Algerian road network. This major project is expected to enhance the socio-economic development of Algeria. However, its first section is implemented within a complex region with very contrasted landscapes marked by mass movements. In the present work, we conducted a mass movement susceptibility assessment on the first section of the road infrastructure using a Multi-Criteria Decision Analysis approach. Various data from different sources were processed in a GIS environment, and nine landslide and rockfall conditioning factors were considered: Lithology, Slope, Daily Temperature Amplitude, Rainfall, Lineament Density, NDVI, Relative Relief, Drainage Density, and Distance to Streams. Each of the conditioning factors was selected, reclassified, and ranked according to its influence on each mass movement type. Two popular GIS-MCDA methods, namely AHP and WLC, were used to weight the influence and combine the selected factors and construct the landslide and rockfall assessment models. Then, landslide and rockfall susceptibility indices were calculated and used to produce mass movement susceptibility maps of the study area. Finally, a spatial analysis was performed to assess the highway section’s susceptibility to the two mass movements. The results show that 22.49% and 12.44% of the road section are highly susceptible to landslide and rockfall hazards, respectively. Finally, the combination of the resulting map with the road chainage enabled the delineation of segments highly susceptible to landslide and rockfall hazards by kilometric points.

The Impact of Fracture Persistence and Intact Rock Bridge Failure on the In Situ Block Area Distribution

The in situ block size distribution is an essential characteristic of fractured rock masses and impacts the assessment of rockfall hazards and other fields of rock mechanics. The block size distribution can be estimated rather easily for fully persistent fractures, but it is a challenge to determine this parameter when non-persistent fractures in a rock mass should be considered. In many approaches, the block size distribution is estimated by assuming that the fractures are fully persistent, resulting in an underestimation of the block sizes for many fracture geometries. In addition, the block size distribution is influenced by intact rock bridge failure, especially in rock masses with non-persistent fractures, either in a short-term perspective during a slope failure event when the rock mass increasingly disintegrates or in a long-term view when the rock mass progressively weakens. The quantification of intact rock bridge failure in a rock mass is highly complex, comprising fracture coalescence and crack growth driven by time-dependent changes of the in situ stresses due to thermal, freezing-thawing, and pore water pressure fluctuations. This contribution presents stochastic analyses of the two-dimensional in situ block area distribution and the mean block area of non-persistent fracture networks. The applied 2D discrete fracture network approach takes into account the potential failure of intact rock bridges based on a pre-defined threshold length and relies on input parameters that can be easily measured in the field by classical discontinuity mapping methods (e.g., scanline mapping). In addition, on the basis of these discrete fracture network analyses, an empirical relationship was determined between (i) the mean block area for persistent fractures, (ii) the mean block area for non-persistent fractures, and (iii) the mean interconnectivity factor. The further adaptation of this 2D approach to 3D block geometries is discussed on the basis of general considerations. The calculations carried out in this contribution highlight the large impact of non-persistent fractures and intact rock bridge failure for rock mass characterization, e.g., rockfall assessment.

Experimental study on the fragment characteristics of marble spheres under repeated impacts

Impact-induced fragmentation of rock blocks is a frequent phenomenon during rockfall hazards, which significantly increases the safety risk to local community and infrastructure. This paper aims to thoroughly investigate the fragment characteristics of rockfall caused by multiple impacts, including the degree of fragmentation and the fragment size distribution. Forty-seven sets of repeated impact tests were conducted using a new impact device. Marble spheres of different sizes repeatedly collided with three types of target plates under various velocities. The mass of each fragment was measured separately after the sphere was broken. It was determined that the fracture patterns of the marble spheres may change with an increase in the impact velocity, which causes a critical velocity to divide the degree of fragmentation of marble spheres into two phases. Above the critical velocity, the degree of fragmentation rose with an increase in the impact velocity. However, below the critical velocity the degree of fragmentation remained steady. In addition, the sphere size and the target plate material also affected the degree of fragmentation for the large spheres with high impact energy. The fragment size distribution depended on the degree of fragmentation, and the ratio of the largest fragment mass to the initial sphere mass decreased with an increase in the degree of fragmentation. A new simple model containing a single parameter with a clear physical meaning was established to describe the fragment size distribution with great accuracy.

Definitions and Concepts for Quantitative Rockfall Hazard and Risk Analysis

There is an increasing need for quantitative rockfall hazard and risk assessment that requires a precise definition of the terms and concepts used for this particular type of landslide. This paper suggests using terms that appear to be the most logic and explicit as possible and describes methods to derive some of the main hazards and risk descriptors. The terms and concepts presented concern the rockfall process (failure, propagation, fragmentation, modelling) and the hazard and risk descriptors, distinguishing the cases of localized and diffuse hazards. For a localized hazard, the failure probability of the considered rock compartment in a given period of time has to be assessed, and the probability for a given element at risk to be impacted with a given energy must be derived combining the failure probability, the reach probability, and the exposure of the element. For a diffuse hazard that is characterized by a failure frequency, the number of rockfalls reaching the element at risk per unit of time and with a given energy (passage frequency) can be derived. This frequency is relevant for risk assessment when the element at risk can be damaged several times. If it is not replaced, the probability that it is impacted by at least one rockfall is more relevant.