Rockfall runout, Mount Cimone area, Emilia-Romagna Region, Italy

Numerous mass movements of different typology characterize both mountainous and piedmont sectors of the Emilia-Romagna Region (Apennine chain, North Italy). Although a less spatially frequent landslide typology within the region, rock falls represent severe threats to buildings, roads and persons due to their high propagation velocity. This paper presents an extract of the Emilia-Romagna regional map of the rock fall runout areas at a scale of 1:25,000. The analysis of rock fall runout areas was based upon a three-dimensional morphological method (TDM). The zone presented in the Main Map encompasses the area surrounding Mount Cimone, in the Emilia-Romagna Region. The proposed regional map of rockfall runout is noteworthy for planning actions and strategies aimed at the prevention and reduction of landslide risk at a regional scale

A fractal fragmentation model for rockfalls

The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-016-0773-8The impact-induced rock mass fragmentation in a rockfall is analyzed by comparing the in situ block size distribution (IBSD) of the rock mass detached from the cliff face and the resultant rockfall block size distribution (RBSD) of the rockfall fragments on the slope. The analysis of several inventoried rockfall events suggests that the volumes of the rockfall fragments can be characterized by a power law distribution. We propose the application of a three-parameter rockfall fractal fragmentation model (RFFM) for the transformation of the IBSD into the RBSD. A discrete fracture network model is used to simulate the discontinuity pattern of the detached rock mass and to generate the IBSD. Each block of the IBSD of the detached rock mass is an initiator. A survival rate is included to express the proportion of the unbroken blocks after the impact on the ground surface. The model was calibrated using the volume distribution of a rockfall event in Vilanova de Banat in the Cadí Sierra, Eastern Pyrenees, Spain. The RBSD was obtained directly in the field, by measuring the rock block fragments deposited on the slope. The IBSD and the RBSD were fitted by exponential and power law functions, respectively. The results show that the proposed fractal model can successfully generate the RBSD from the IBSD and indicate the model parameter values for the case study.Peer ReviewedPostprint (author's final draft

Unstable Slope Management Program

INE/AUTC 11.1

Surface movement and cascade processes on debris cones in temperate high mountain (Picos de Europa, northern Spain)

Producción CientíficaDebris talus is a very common landform in the temperate high mountain, so much so that it is the most representative of the periglacial and nival processes. This work studies debris cones in the Picos de Europa, an Atlantic mountain range in the north of the Iberian Peninsula. A detailed geomorphological map was prepared, fieldwork was carried out on the debris cone surface, the ground and air thermal regime was analyzed, and a five-year Terrestrial Laser Scan survey carried out. Annual volume changes on the surface of the debris cones were detected and related to active processes and sediment transfer. Two different behaviors were observed in each cone. Cone A is linear, with equilibrium between accumulation and sediment transfer, while Cone B is concave-convex denoting accumulation processes in the upper part deriving from the greater frequency of snow avalanches. Changes in morphology surpass 50 cm/year with most of the activity taking place in the highest and lowest areas. The presence and action of the ice on the debris slope are moderate or non-existent and freeze-thaw processes are only active on the walls at over 2000 m a.s.l. The main processes on debris cones are debris flow and creep related to snowcover, but sediment transfer on the slopes involves high intensity-low frequency (debris flow, avalanches) and high frequency-low intensity processes (creep, shift, solifluction and wasting).Ministerio de Economía, Industria y Competitividad - Fondo Europeo de Desarrollo Regional (project CGL2015-68144-R)Junta de Extremadura - Fondo Europeo de Desarrollo Regional (project GR10071

Improvment of safety conditions of unstable rock slopes through the use of explosives

The paper discusses operations aimed at creating a safer natural or man made rock slope by artificially inducing the displacement of unstable elements by blasting. A detailed analysis of the problems with the use of explosives present when conducting these activities is carried out focusing on the advantages and disadvantages of this technology. The results of two examples of demolition of instable rock elements are presented and discussed thus providing suggestions for future blasting design

Experimental testing of low energy rockfall catch fence meshes

Flexible catch fences are widely used to protect infrastructure like railways, roads and buildings from rockfall damage. The wire meshes are the most critical components for catch fences as they dissipate most of the impact energy. Understanding their mechanical response is crucial for a catch fence design. This paper presents a new method for testing the wire meshes under rock impact. Wire meshes with different lengths can be used and the supporting cables can be readily installed in the tests. It is found that a smaller boulder causes more deformation localisation in the mesh. Longer mesh length makes the fence more flexible. Under the same impact condition, the longer mesh deforms more along the impact direction and shrinks more laterally. Supporting cables can reduce the lateral shrinkage of the mesh effectively. Most of the impact energy is dissipated by stretching of the wires. Wire breakage has not been observed

A Robust and Cost-Efficient Design of Lightweight Rockfall Catch Fences for Railways

Trains and railway infrastructure are subjected to serious potential hazards from detached falling rock(s) in mountain regions worldwide. This can lead to severe damages, casualties and significant delays. In 2011, a rockfall event at Stromeferry bypass in Scotland caused 4 month railway closure that led to a negative impact on local businesses and the repair work cost was £3.2 million. Rock catch fences are widely used in protecting roads, railways and infrastructure from rockfall hazards. A typical design comprises of a high tensile strength wire mesh that is anchored to the ground by rigid posts and strengthened to the lateral and upslope sides by anchoring tension cables. These systems are categorised by the ability to dissipate the kinetic energy of falling rock(s). Due to the lack of a practical design code, these systems are designed primarily by experience and engineering judgement, which makes the design either dangerous or highly conservative. Indeed, engineers found that the current design tend to be highly conservative which makes the costs for materials and construction too high. There is an urgent need to improve the current design based on extensive experimental tests and advanced finite element modelling. This study presents the development of a lightweight rock catch fence design

Multi-scenario rockfall hazard assessment using LiDAR data and GIS

Transportation corridors that pass through mountainous or hilly areas are prone to rockfall hazard. Rockfall incidents in such areas can cause human fatalities and damage to properties in addition to transportation interruptions. In Malaysia, the North–South Expressway is the most significant expressway that operates as the backbone of the peninsula. A portion of this expressway in Jelapang was chosen as the site of rockfall hazard assessment in multiple scenarios. Light detection and ranging techniques are indispensable in capturing high-resolution digital elevation models related to geohazard studies. An airborne laser scanner was used to create a high-density point cloud of the study area. The use of 3D rockfall process modeling in combination with geographic information system (GIS) is a beneficial tool in rockfall hazard studies. In this study, a 3D rockfall model integrated into GIS was used to derive rockfall trajectories and velocity associated with them in multiple scenarios based on a range of mechanical parameter values (coefficients of restitution and friction angle). Rockfall characteristics in terms of frequency, height, and energy were determined through raster modeling. Analytic hierarchy process (AHP) was used to compute the weight of each rockfall characteristic raster that affects rockfall hazard. A spatial model that considers rockfall characteristics was conducted to produce a rockfall hazard map. Moreover, a barrier location was proposed to eliminate rockfall hazard. As a result, rockfall trajectories and their characteristics were derived. The result of AHP shows that rockfall hazard was significantly influenced by rockfall energy and then by frequency and height. The areas at risk were delineated and the hazard percentage along the expressway was observed and demonstrated. The result also shows that with increasing mechanical parameter values, the rockfall trajectories and their characteristics, and consequently rockfall hazard, were increased. In addition, the suggested barrier effectively restrained most of the rockfall trajectories and eliminated the hazard along the expressway. This study can serve not only as a guide for a comprehensive investigation of rockfall hazard but also as a reference that decision makers can use in designing a risk mitigation method. Furthermore, this study is applicable in any rockfall study, especially in situations where mechanical parameters have no specific values

Paying for Safety: Preferences for Mortality Risk Reductions on Alpine Roads

This paper presents a choice experiment, which values reductions in mortality risk on Alpine roads. These roads are on one hand threatened by common road hazards, on the other hand they are also endangered by natural hazards such as avalanches and rockfalls. Drawing on choice data from frequently exposed and barely exposed respondents, we are not only able to estimate the VSL but to explore how the respondents differ in their individual willingness-to-pay depending on personal characteristics. To address heterogeneity in preferences for risk reduction, we use a non-linear conditional logit model with interaction effects. The best estimate of the VSL in the context of fatal accidents on Alpine roads is in the range of €4.9–5.4 million with distinct differences between the urban and the mountain sample groups. We find the VSL to be significantly altered by socio-economic factors but only marginally altered by the type of hazard.Value of Statistical Life, Choice Experiment, Natural Hazard Mitigation, Traffic Safety