Rockfall Hazard Rating System Research Articles

Assessment of landslide Possibility Index and Rockfall Hazard Rating System for Slopes in Qaywan Mountain, Sulaimani Governorate, Northeastern Iraq

The current study includes assessing road risks using a system Landslide Possibility Index (LPI) and Rockfall Hazard Rating System (RHRS) analysis along the Qaywan Mountain (anticline) main road 20 km north of SulaimaniGovernorate. Slope stability assessments consisted of seventeen stations along the main road in the study area. Along the outcropped rock units represented by formations, Balambo, Sarmord, Kometan, and Shiranish, a thorough discontinuity assessment and a regional survey of slopes were carried out. Along the cut slopes, rockfall is the primary type of failure, in addition to possibility types of landslide failures in the studied area is plane sliding, wedge sliding, and toppling because cutting rocks to build roads, slope direction and slope angle, dip and dip direction of discontinuities. The (LPI) indicates all the slopes studied in 17 sites in the surveyed area along the road were classified as high hazard. According to the analysis results of the RHRS, the score ranges between 177 and 375. Site no. 5 (375) has the highest rating value indicating a moderate hazard that requires remedial measures to be taken with a moderate level of urgency and site no.8 has the lowest value noted (177). It is the only site that falls under this rating, which is classified as a low hazard and slopes do not require detailed studies.

An Analysis of Slope Stability in the Penipe–Baños Road by Applying Empirical Methods, Kinematic Analysis and Remote Photogrammetry Techniques

The purpose of this work is to analyze the stability of four slopes along the Penipe–Baños road, which is situated in the provinces of Chimborazo and Tungurahua and where there are occasionally rockfalls that hinder passage and endanger road users. The methodology used to conduct the analysis was based on data collection with the help of remote techniques such as structure from motion, which allows us to obtain slope data using photogrammetry. Empirical methods such as slope mass rating, Q-slope, the kinematic method and the Rockfall Hazard Rating System method were used. These methods were evaluated with Rocfall3 software for the analysis of the fall trajectory of rock blocks. The results of this work show that the slopes studied do not represent a greater risk to the road than other slopes close to those studied, but these could not be analyzed due to their lack of accessibility and the danger of obtaining data under those conditions. The study of these different methods demonstrates the reliability of low-cost, remote techniques in the facilitation of analysis in places with similar conditions.

Development of a risk mapping along a railway

The Ramal Trem Turístico (RTT), a 17 km long railway between Ouro Preto and Mariana, a centenary line, currently in operation as a tourist attraction with historical importance. The railroad was built along a steep region, with hundreds of slopes, and eventually slope instabilities compromised the tour. In linear infrastructure projects, a risk assessment is an important tool for risk management, mapping it is the first step. After slope instabilities in 2019, a risk map was elaborated early 2021 for RTT. Risk is obtained by multiplying the probability of a certain event to occur by its consequences. Define its value in a quantitative way demands geotechnical investigation, for precise failure probability. Regardless of its importance, its determination needs high resources, specially for linear infrastructure in a region with heterogeneous geology and pedology. Therefore, for the risk mapping of the RTT, a semi-empirical methodology was adopted, based on the Rockfall Hazard Rating System (RHRS), originally developed for rocky slopes, and adapted for the registration of slopes in soil and in landfill. The aim of the method is to register a series of slope characteristics to be assigned a specific score, framing the slopes within pre-defined risk classes. This methodology was applied to this 17 km railway and identified 286 slopes. In January 2022 extreme rainfall triggered slopes instabilities at RTT. A critical analysis of this event shows a satisfactory result for the applied methodology. Risk mapping is an important tool for risk management, helping to prioritize investments in mitigation measures.

Comparison of Rating Systems for Alberta Rock Slopes, and Assessment of Applicability for Geotechnical Asset Management

In 1999, Alberta Transportation and Economic Corridors (TEC) implemented the Geohazard Risk Management Program (GRMP) to identify, assess, monitor, and prioritize the mitigation of risk resulting from geohazard events at specific sites along the provincial highway network. The GRMP was developed to address a variety of geohazard types including rockfall hazards that occur at natural and constructed (cut) highway backslopes. An evaluation of various methods for the condition assessment of rockfall geohazards, including TEC’s current GRMP risk rating system, has been completed with the intent of better understanding the suitability of each method as TEC transitions to a formalized GAM program. The GRMP risk rating values for selected rockfall geohazard sites along highway corridors in Alberta were compared to values developed from the results of five established rock mass and rock slope rating systems. The results of this study demonstrate that TEC’s current GRMP risk rating system is a viable tool for the condition assessment and performance monitoring of rockfall geohazards, which could be utilized within a formalized GAM program, further benefitting from years of recorded application in Alberta. Of the other rating systems tested, the rockfall hazard rating system (RHRS) showed a strong correlation with the GRMP risk rating while Q-Slope, the Geological Strength Index (GSI) and Rock Mass Rating (RMR) correlation were marginal but displayed a potential for use as condition assessment tools. The work presented in this paper provides the first evaluation of rock slope rating systems for rockfall hazards along corridors in Alberta, directly comparing them to the slope performance as observed by TEC in a quantitative manner.

Classification of Risks for Landslides in Slopes and Hillsides of Volcanic Nature in Macaronesia and Their Application to the Canary Islands

Due to their genesis, volcanic rocks present some singularities that make their geotechnical characteristics significantly different from other more common types of massifs, such as sedimentary and metamorphic rocks. The formation mechanisms of volcanic rocks are varied, rapid, and, in general, of high energy. These processes give this type of rock a geotechnical behaviour and geomechanical properties that are totally different from those of other nonvolcanic materials, derived from their high heterogeneity and anisotropy. There are voids and cavities due to the alternation of strata of different competences and resistances, or susceptibility to erosion, and discontinuities and joints of very different genesis (of thermal origin, by mechanical forces, by erosive processes or by shrinkage—recrystallization). The phenomenology of the instability of blocks and stones is variable, which makes it very difficult to establish simple and concrete methodologies or procedures to study and analyse this problem. To date, the estimation of the risk of this type of phenomenon has been quantified using empirical methodologies; this approach is considered to be the most operative in responding to such a complex phenomenology in which a multitude of factors intervene. In the field of roads, the most widely used methods are RHRS and RHRON. Therefore, a new rockfall risk classification based on the RHRS (Rockfall Hazard Rating System) methodology is proposed in this article and specifically applied to the Canary Islands region.

Interaction between Rockfalls and Vehicles Studied for Speed Limit Zonation along Mountainous Roads

A rockfall risk assessment along the transportation route to a historical village is presented herein with the aim of evaluating the potential of this approach for speed limit zonation. Mountainous roads are often subject to rockfalls, which should be taken into account for territorial management and planning, especially when dealing with dynamic variables, such as vehicular traffic. Rockfall risk analysis along roads is often aimed at assessing a risk value to plan or prioritize mitigation purposes. Nevertheless, such approaches can also be used to regulate traffic in terms of posted speed limits. Traffic is, indeed, a key variable in rockfall risk analysis due to the spatial and temporal correspondence that a vehicle can have with an either falling or fallen rock block. In order to address this relationship for speed limit zonation purposes, in this paper, a semi-quantitative Rockfall Hazard Rating System was applied to a mountainous road leading to a popular tourist destination in eastern Sicily (Italy), which is characterized by winding paths. This approach, which was chosen for its feasibility and international diffusion, was repeated by taking five different vehicle speed scenarios into account, thus providing an innovative application of the procedure in terms of aims and practical results. The achieved outcomes were used to draft thematic maps, as well as to define a suitable speed limit zonation related to the rockfall risk, highlighting that the road visibility strongly affects the final results. The achieved outcomes demonstrate how a scientific approach can be turned into a practical tool of broad utility, especially in mountainous settings, where winding roads and rockfall problems often condition the viability.

Modified “Rockfall Hazard Rating System for Pakistan (RHRSP)”: An Application for Hazard and Risk Assessment along the Karakoram Highway, Northwest Pakistan

Rockfall is a natural mountain hazard posing a severe threat to people, infrastructure, and vehicles along the transportation corridors. In this research, the standard Rockfall Hazard Rating System (RHRS) is slightly modified for the mountainous terrains of Pakistan through the quantification of animal activity along the highways. In the modified Rockfall Hazard and Rating System for Pakistan (RHRSP), animal activity is scored based on permanent and random animal tracks, shallow and higher altitudes, and shoulder width. The model is applied along the Karakoram Highway (KKH), which traverses a suture between Besham and Dasu (≈78 km), for Rockfall hazard and risk assessment mapping. An inventory of rockfalls, topples, and debris slides is compiled at 30 stations. Results show that rockfalls are mostly of the wedge and topple type failures. Fifty-seven percent of the area falls under the very-high to high hazard zone, 18% under moderate hazard, and 25% covers the low to very low hazard zone. Sixty-seven percent of the stretch is at very-high to high risk, distributed from Dubair to Dasu. The main reason for this risk is associated with narrow road width and limited shoulder width for vehicles. The RHRSP model is also applicable for other highways with the same geological and morphological settings.

ANALISIS BAHAYA, LINTASAN, DAN SISTEM PROTEKSI TERHADAP POTENSI LONGSORAN TIPE JATUHAN BATU PADA LERENG BANGUNAN PELIMPAH BENDUNGAN TUGU, JAWA TIMUR

The construction of the Tugu Dam spillway does not escape the problem of slope instability, especially the rock fall type landslide as a result of the rock slope cutting work at STA+80. The purpose of this study was to determine the characteristics of the rock discontinuity area and the solutions needed to address the potential hazards of rock fall on the slopes of spillway structure. In this study, a semi-quantitative method conducted based on the Rockfall Hazard Rating System (RHRS) which is carried out by identifying outcrops on rock slopes. Determination of the rock fall trajectory, was conducted by statistical methods on rock mass based on changes in velocity when rocks roll, slide, and bounce. Geologically, the research area belongs to the Mandalika Formation. Based on the RHRS weighting, the total score on the STA+80 slope is 399, which means that the slope needs to be repaired or given safely with a moderate level of urgency. The rock fall trajectory modeling at the measurement location X = 121,875 has a kinetic energy of 973.14 kJ andesite and 72.59 kJ of volcanic breccia, for high results of 0.43 meters of andesite reflection and 2.04 meters of volcanic breccia, and velocity results translational velocity obtained at 33.8 m/s andesite and 8.67 m/s volcanic breccia. The potential for rock fall requires a safety system with a type of retained flexible barriers with a height of 5 meters that can be applied to the toe of the slope.Keywords: rock fall, discontinuity, trajectory, protection system, Tugu Dam

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.

Investigation into the Rockfall Hazard along Lengpui-Aizawl Highway, NH-44A, Mizoram, India

Rockfall is a critical problem in the hilly regions. The Lengpui-Aizawl highway has witnessed many rockfalls and other types of landslide events in the past few years. This highway is imperative to the area as it links the Lengpui airport with the city. Most of the rock slopes along this highway are prone to rockfall, thus requires proper investigation. In this study, an investigation into the rockfall hazard was carried out on the nine rock slopes using the rockfall hazard rating system (RHRS) approach along NH-44A. Based on an extensive field investigation, the analysis shows that two out of nine slopes are more hazardous than the others as the RHRS score for these slopes is higher than 500. Furthermore, rockfall simulations were performed for hazardous slope to quantify the risk in terms of bounce height, velocity, kinetic energy and maximum reach of falling rock blocks. The simulation result reveals that vehicles on the roadway are under continuous threat. The potential falling blocks have a kinetic energy of 196 kJ which is enough to damage the buildings, vehicles and fatalities.

Empirical assessment of rockfall and debris flow risk along the Karakoram Highway, Pakistan

The Karakoram Highway links north Pakistan with southwest China. It passes through unique geomorphological, geological and tectonic setting. This study focused 200-km-long section of the highway starting from Besham until Chilas. Landslides are frequent and are mostly triggered by torrential rain during Monsoon and Westerlies, leading to highway blockade. Rockfall and debris flow are prime mode of slope failures. Regional to site-specific approach was implemented to assess risk associated with these two modes. Remote sensing-based techniques were used to identify potential hazardous sites, which were further investigated for risk assessment. Modified Pierson’s rockfall hazard rating system (RHRS) rated potential rockfalls, whereas semi-quantitative technique was employed to assess debris flows. Normalized scores of each site shaped the final map, further classified into four zones: very high, high, intermediate and low risk.

Assessment of Rockfall Hazard and Stabilization of Rock Slope Surface at the World Heritage Ajanta Cave

The assessment of rock fall hazard of a natural rock slope surface with ancient rock cave monuments of historic importance at World-Heritage site of Ajanta in the state of Maharashtra in India, embedded in basaltic rock formation is carried out and presented. In past the site has witnessed many small and large scale rock falls in the form of boulders which could cause the loss to the ancient rock caves of historic importance as well as en-dangering the visitor’s safety. The main cause of the rock fall is dislocation of the boulders from the natural rock surface slopes due to heavy rainfall as well as due to erosion, rock weathering, trees roots widening etc. In the present study, the rock slope surface and dislocated boulders vulnerability to failure risk is carried out with the Rockfall Hazard Rating System (RHRS) in tandem with other empirical approaches available for rock mass classification. The study using rockfall hazard rating system requires tedious field-work due to the involvement of a large number of parameters and long-stretch of the site under question. The detailed field study is carried out for the evaluation of various parameters involved in the RHRS as well as that of various empirical approaches applied. In the case of the cumulative RHRS score is more than 500 which implies that the slope surface or critical boulder site is unstable, prone to failure and need immediate attention for remedial measures. Accordingly, stabilization measures are planned on the priority basis.

HAZARD ASSESSMENT OF SLOPE FAILURES IN CONGLOMERET AT TIKRIT, NORTHERN IRAQ

The degree and nature of slope failure hazards reflected the rock properties of unstable slopes, effective characteristics as slope high, slope angle, rock discontinuities, weathering, presence of water, and the consequence level depend on several parameters. Ditch (width, shape, volume), traffic, shoulder width to decide slopes mode and rest rock properties. Applying the Missouri Rock Fall Hazard Rating System Failure types happened and probably in the research area (Rock Fall, Toppling, Rolling). Nature parameters control hazard cases, station 7 represented alone the Tikrit bridge, water contact along a year, western shoulder of the bridge near the cliff, traffic problems, man-made, and buildings above slope apex, stations 4 and 5 people using Al-Bilaj area for swimming, fishery, and tourism, stations 1, 2, 3 and 6. Human activities are less than at stations 4 and 5. Consequently, the study area is sufferings hazard, and so should include warning suddenly failures. Stations1, 6 and 7 were classified as High-Risk High Consequence, while 2, 3, 4 and 5 were classified as High-Risk Low Consequence

Rockfall Hazard Assessment Around Ankara Citadel (Turkey) Using Rockfall Analyses and Hazard Rating System

Ankara Citadel which is one of the important cultural heritages in Turkey settles in the oldest part of Ankara. Rockfall event has occurred around the Citadel located on a steep hill where andesite is exposed. The rockfall problem causes a great risk to the surrounding area where road, school, floral shops, car parking. Therefore, the major aim of this research is to reveal the rockfall risk around the castle. The rockfall problems around the Ankara Citadel may be linked with weathering, freezing–thawing, earthquake, and cooling joints, and effects or combination of these in the rock units. The rockfall-related hazard at the Citadel is assessed by 2-D rockfall analyses along several profiles in this investigation. Field observations and stability analyses (kinematic and limit equilibrium) of the slopes reveal that there exist many blocks ready to fall down. Four different andesite block sizes measured in the field are separately analyzed on the basis of bounce height, fall-out distance, velocity and kinetic energy of the blocks. The obtained data are evaluated to define the possible rockfall-based hazard zones. Based on the danger zones acquired from the rockfall analyses, the removal of the fallen and loosen andesite blocks and the installation of catch barriers with suggested properties are recommended. Besides, the risk integrated into rockfall hazard rating system on the basis of structural and morphological criteria of the rock mass reveals that medium risk category to be mitigated by light remedial measures for the indicative protection exists in the study area.

Comparing rockfall hazard and risk assessment procedures along roads for different planning purposes

Hazard and risk assessment procedures of different types of rockfall were analyzed to compare their outcomes when they are applied to the same case study. Although numerous methodologies are available in literature, rockfall hazard and risk analyses are often limited to standard estimations, affected by a margin of uncertainty, especially when relevant engineering projects are about to be realized. Based on the design purpose, different types of approaches can be chosen among the qualitative and quantitative ones available in literature, which allow different levels of analysis. One of the main criticisms related to rockfall events is the risk affecting linear structures, such as road or railways, due both to their strategic relevance for trade and communications and to the great entity of the exposed value (traffic units) traveling along them. In this perspective, a comparison between the qualitative method known as Evolving Rockfall Hazard Assessment (EHRA), the semi-quantitative modified Rockfall Hazard Rating System (RHRS) and the quantitative Rockfall Risk Management (RoMa) approach is herein commented according to a practical application to a case study. It is the case of the rockfall threat along slopes crossed by a strategic road connecting two of the most known spots of eastern Sicily (Italy), at the Taormina tourist complex. Data were retrieved from both recent literature and technical surveys on field. Achieved results highlight how the approaches are affected by a different level of detail and uncertainty, arising also by some necessary assumption that must be taken into account, especially when mitigation measures or territory planning have to be designed. Achieved results can be also taken into account for similar studies worldwide, in order to choose the most suitable procedure based on the design purpose. This is indeed crucial in the perspective of the optimization of time and economic resources in the territorial planning practice.

Theoretical Models of Slope Stability Analysis in The Maqlub Mountain Rock Cut Routes, North Iraq

In many sections, the road leading up to the top of Maqlub Mountain is dangerous due to the fall of several rocks. There were six locations recognized for this dynamic geological process, rockfalls of varying sizes, with very large measurements up to 230 x 120 x 110 cm are falling on the road. The study suggested three theoretical models explain the causes of rockfall, through a ‎comprehensive study in the area. The first model showed that the cause of rockfall was the presence ‎of rocky slopes with a reverse slope. The second model has shown that the rockfall is caused by weak engineering properties of marl beds and it can be squeezed under thick and fractured ‎beds of hard and fractured limestone rocks. The third model determined the small area of the rock base at the rocky slope surface and its large height that reduced their stability. A field survey was performed to study an area that included measuring the height and inclination of the slope surface and measuring the attitude of all discontinuities and their engineering characteristics to classify the slope stability, as well as the technical parameters of the road that determine the risk and consequence factors. Two computer programs were designed to evaluate slope stability, one used to classify risk and consequence (Rockfall Hazard Rating System Program) and the other to classify slope stability based on its geotechnical properties (Slope Mass Rating System Program) in addition to the areas where a rock climb previously occurred, the study concluded that dangerous sites have been recognized along the road to Maqloub Mountain. ‎The size of the falling rock cuttings was classified between small and medium size. ‎The study indicated that this road requires support in hazardous locations to prevent accidents causing losses of property and humans.

RMR and RHRS of Ngaizel Road cutting section, Aizawl, Mizoram

Due to unfavourable topographical features roads in hilly areas are usually small as compared to plain areas, therefore several problems may arise whenever rockfall occurs. One of the busiest domestic road in Aizawl i.e. Ngaizel road often encountered rockfall along its cutting slope. This road act as an important gateway which connects the southern parts of Mizoram. This road is packed with human activities which adds on the hazard level to rise high. The main factors that contribute to rockfalls include slope degree, geomechanical properties of rock mass and anthropogenic activities. Taking into consideration of all the adverse effect of rockfalls, RMR (Rock Mass Rating) become indispensable to identify the actual condition of rock mass on the slope of the study area. RMR classification is carried out to determine the geomechanical condition of slope rock mass and Rockfall Hazard Rating System (RHRS) is applied for identifying the hazard-prone area of rockfall along the cut slope of Ngaizel road. RHRS depends on various parameter which include slope height, annual precipitation, block size, block volume, decision sight distance, average vehicle risk, road width and rockfall history which mainly concern about the safety of pedestrians along the road. The RMR and RHRS study along Ngaizel cut slope provides a detailed and useful information about the geological condition and delineating the hazard level. The study also gave awareness and alertness about the actual condition of the area.

Digital Surface Model-aided Quantitative Geologic Rockfall Rating System (QG-RRS)

ABSTRACTRockfalls are one of the most common types of slope failures that affect cut slopes along roadways in mountainous regions. The Rockfall Hazard Rating System (RHRS), started in Oregon and adopted by various U.S. states, is used to rate cut slopes with respect to their likelihood of releasing rockfalls. Existing rating systems use semi-quantitative approaches to rate geological and non-geological factors. The main geologic factors are favorability/unfavorability of orientation of discontinuities with respect to the orientation of slope faces and likelihood of differential weathering leading to undercutting of strong rock units. Digital surface models (DSMs) derived from light detection and ranging (LiDAR) and photogrammetry have been used to remotely characterize rock mass. This research introduces an expanded application of DSMs to quantify geologic factors that contribute to the likelihood of rockfall events. The method is hence referred to as the Quantitative Geologic Rockfall Rating System (QG-RRS). Four DSM-based parameters, A, B, C, and D, have been identified to evaluate geologic factors. These parameters quantify the likelihood of discontinuity orientation-controlled failures (parameter A), the degree of undercutting (parameter B), rockfall activity based on rockfall release surfaces (parameter C), and rockfall volume from rockfall voids (parameter D). This rating system, although not inclusive of other non-geological factors, appears to provide reproducible quantitative estimation of geologic factors that control rockfall generation.

Investigation of rockfall-prone road cut slope near Lengpui Airport, Mizoram, India

Rockfall is one of severe natural hazards that are frequently reported in northeast region of India. It carries rock block falling from the cliff with high velocities and energies which can result in damages to vehicles, disruption to transportation, injuries and fatalities. The massive rockfall event which occurred in April 2017 on the highway NH-44A, near Lengpui Airport, blocked the traffic for 1 d, and fortunately, no casualties were reported as the event occurred in the night. This is the only highway connecting the Aizawl city to the airport and the region is highly prone to rockfall events. Hence assessment of rockfall along this highway is necessary. In the current study, rockfall hazard assessment has been carried out on three locations by rockfall hazard rating system (RHRS). During pre-failure analysis, the result shows that most hazardous slopes have RHRS score of 639. The slopes were found to be vulnerable and later on the rockfall activity occurred. Three-dimensional (3D) stability analysis has been carried out using 3DEC software package to analyze the failure behavior and to decide the rockfall-prone zone (unstable blocks) for slope. The total displacement of 2.24 cm and velocity of 2.25 mm/s of the failed block have been observed in the numerical analysis. Further, the rockfall vulnerable zone (unstable blocks) is considered to determine the parameters such as run-out distance, bounce height and energies of the falling rock blocks. The maximum total kinetic energy of 5047 kJ has been observed in the numerical analysis with the maximum run-out distance up to 18 m.

Rockfall Hazard Rating System(s) in Saudi Arabia – A Review

Slope instability along highways in mountainous areas is not only a major hazard for lives and passing vehicles but also may hinder traffic for long period and thus create significant economic loss. The most common type of slope instability failures in such areas is rockfalls. Many qualitative rockfall hazard rating systems (RHRSs) have been developed across the world. However, the Middle East almost lacks to such systems. For instance, in Saudi Arabia, which has the largest economy in the region, only one system of rockfall hazard rating system (RHRS-SA) has been developed up to now. This paper aimed to critically review this system. Some drawbacks were found in the RHRS-SA. However, the main disadvantage was that the final rating score of risk is not consistent with risk definition. In sum, the remarkable findings of this review can be accounted either for any future modifications for the RHRS-SA or to develop a new rockfall hazard rating system but for a specific area(s) in Saudi Arabia.