Some Remarks on the Use of Deterministic and Probabilistic Approaches in the Evaluation of Rock Slope Stability

The rock slope stability assessment can be performed by means of deterministic and probabilistic approaches. As the deterministic analysis needs only representative values (generally, the mean value) for each physical and geo-mechanical parameter involved, it does not take into account the variability and uncertainty of geo-structural and geo-mechanical properties of joints. This analysis can be usually carried out using dierent methods, such as the Limit Equilibrium method or numerical modeling techniques sometimes implemented in graphical tests to identify dierent failure mechanisms (kinematic approach). Probabilistic methods (kinetic approach) aimed to calculate the slope failure probability, consider all orientations, physical characters and shear strength of joints and not only those recognized as kinematically possible. Consequently, the failure probability can be overestimated. It is, therefore, considered more realistic to perform both kinematic and kinetic analyses and to calculate a conditional probability given by the product of the kinematic and kinetic probabilities assuming that they are statistically independent variables. These approaches have been tested on two rock slopes in the Campanian region of Southern Italy aected by possible plane and wedge failures, respectively. Kinematic and kinetic probabilities have been evaluated both by means of the Markland’s test and the Monte Carlo simulation. Using the Eurocode 7, also a deterministic limit equilibrium analysis was performed. The obtained results were compared and commented on

Loss of life risk due to impacts of boulders on vehicles traveling along a very busy road.

The paper is aimed to describe the used approach for calculating the risk along a road stretch belonging to a very busy coastal road in Southern Italy. During the time span 1969-2013, 22 rockfalls affecting this road were inventoried. On 18th February 2014 a new rockfall happened and several boulders reached the northern lane of the road. On the basis of collected data concerning the landslide hazard and road vulnerability, a procedure for the probability evaluation of a fatal accident - for a road user - is presented, discussed in details and compared. The analysis is meant to allow the design of appropriate protection devices along the cliffs overhanging the road

DinSAR monitoring of the landslide activity affecting a stretch of motorway in the Campania region of Southern Italy

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Il contributo della geologia e della geotecnica nel ripristino dei terrazzamenti dell'area amalfitana

Il lavoro analizza le caratteristiche geomorfologiche, stratigrafiche e geotecniche dei versanti terrazzati nell’area di Amalfi-Ravello (23 km2) e le relative condizioni di stabilità, allo scopo di individuare le cause principali che determinano il collasso dei manufatti. In base ad una serie di sopralluoghi in campo finalizzati all’individuazione delle dimensioni delle opere murarie e di prove fisico-meccaniche in laboratorio sui terreni piroclastici sostenuti dalle macére, sono state condotte verifiche di stabilità, sia in condizioni statiche che dinamiche, valutando anche l’effetto della spinta aggiuntiva imputabile alla formazione di accumulo d’acqua temporaneo a tergo del muro. Lo studio ha evidenziato che, in presenza di eventi critici ed accumulo d’acqua a tergo del muro dovuto ad un cattivo funzionamento del sistema di smaltimento delle acque piovane, si verifica un’instabilità locale che può comportare il tranciamento o il ribaltamento del muro. Tali condizioni possono giustificare l’innesco di fenomeni di colata rapida che interessano frequentemente ampie porzioni di versante. Pertanto, ne deriva la necessità di prevedere: l’istallazione di sistemi di canalizzazione che allontanino le acque meteoriche impedendone l’infiltrazione a tergo del muro; un ‘ordinaria manutenzione dei sistemi di drenaggi del manufatto stesso. Tenuto conto dell’estensione dei terrazzamenti nell’area di studio (circa 163 km) e dell’abbandono delle antiche pratiche agronomiche in molte zone difficilmente raggiungibili, si ritiene che questi interventi possano migliorare, in molti casi, la stabilità globale di questi territori antropizzati ma fortemente vulnerabili

Rockfall and sustainable development in the Sorrento-Amalfi peninsula

Based on an inventory of 721 rock landslides happened in the time span between 1899 and 2019 (120 years), the rockfall susceptibility affecting the Sorrento-Amalfi Peninsula has been evaluated. Both wide rock landslides (e.g.: Amalfi 1899, M. Catiello 2002) and small movements involving cliffs only a few hundred square meters wide, affect this area. Landslide data from different sources (IFFI Catalogue, bibliography, newspapers, websites, and onsite surveys) were processed to obtain the areal rockfall density (number of landslides/km2) of an area of about 303 km2 (including Capri), divided into 33 municipal territories. Also, the linear densities (number of landslides/km) for the two main state roads crossing the region (no. 163 Amalfitana and no. 145 Sorrentina), and coastline were evaluated. Even though there were an incomplete information concerning many failures, it was possible to draw susceptibility maps, the contents of which are explained and commented below. These maps can be considered useful tools for promoting the sustainable development of the area

Application of the Swiss Federal Guidelines on rockfall hazard: a case study in the Cilento region (Southern Italy)

On December 15, 2008, a rock slide of approximately 4,000 m3 occurred near San Severino di Centola (Cilento, Province of Salerno). The landslide occurred along very steep bedding planes intersected by tectonic joints affecting a rocky cliff. The landslide debris, formed by several boulders, came to a halt along the gentler slope below. Many blocks reached the slope base including the national road n° 562 and injuring a motorist on the road. Furthermore, the road suffered heavy damages causing a halt in traffic for many weeks. Several signs of the impacts were detected along the slope and on the road; also, the volumes of some boulders were measured. The area affected by block trajectories stretch down slope about 4,900 m2. By means of 2D and 3D trajectory codes using the “lumped-mass” method, it was possible to estimate more suitable impact energy restitution and rolling friction coefficients, to reconstruct rock fall trajectories, and to calculate total kinetic energies. Extending to the surrounding slope (surface about 2 ha) these data, a hazard scenario was carried out, displaying the pattern of iso-energy distribution curves calculated along 11 critical profiles, and zones exposed to 70% and 30% of frequencies of block transits and endpoints. Successively, with reference to the Swiss Federal Guidelines, another scenario was prepared on the basis of rock fall intensity values and the return period of the 2008 landslide event. In this way, it was possible to define areas of high, moderate and low hazard. The degrees of hazard are assigned according to their consequences for construction activity and outline zones where additional protection is required. The construction of a retaining embankment was believed suitable for local risk mitigation

Valutazione della pericolosità da crollo secondo le normefederali svizzere: il caso di San Severino di Centola (Cilento)

Il 15 dicembre 2008, una frana del volume di circa 4000 m3 interessò una scarpata rocciosa, in prossimità dell’abitato di San Severino di Centola, nel Cilento meridionale. L’evento, del tipo scorrimento traslativo, avvenne lungo piani di stratificazione fortemente inclinati ed intersecati da numerose fratture. Il cumulo di frana, formato da numerosi blocchi, si arrestò lungo il settore medio-basso del pendio sottostante. Diversi massi raggiunsero la base del pendio, invadendo la strada nazionale n. 562 e coinvolgendo un’auto in transito. A seguito della frana, la sede stradale ha subìto gravi danni ed è stata chiusa al traffico per diversi mesi. Subito dopo l’evento, lungo il pendio sottostante la scarpata rocciosa e sulla sede stradale, furono rilevate numerose impronte da impatto; inoltre, furono misurati i volumi di numerosi massi. L’area interessata dalle traiettorie di caduta si estende su di una superficie di circa 4.900 m2. Con l’ausilio di codici di calcolo bi e tridimensionali, sono state effettuate numerose analisi traiettografiche, allo scopo di definire i valori dei coefficienti di restituzione all’urto e dell’angolo d’attrito al rotolamento più realistici. Inoltre, sono state ricostruite le traiettorie di caduta massi e calcolati i valori di energia cinetica. Estendendo all’area circostante (superficie pari a circa 2 ettari) i risultati delle analisi, è stata allestita una mappa di pericolosità. Su tale mappa sono state tracciate le curve iso-cinetiche calcolate interpolando i dati di energia rilevati lungo 11 profili topografici. Inoltre, sono rappresentate le aree interessate dal 70 e 30% di frequenza di transito ed arresto dei massi. Successivamente, con riferimento alle Norme Federali Svizzere, è stato allestito un altro scenario di pericolosità, coerente con il primo, basato sui valori di intensità e periodi di ritorno dell’evento del 2008. In questo modo è stato possibile delimitare le aree caratterizzate da diverso grado di pericolosità e definire i tipi di interventi più idonei per la mitigazione del rischio

Stability of an undercut sea-cliff along a Cilento coastal stretch (Campania, Southern Italy)

This paper deals with a finite element stability analysis performed on a sea-cliff affected by a deep notch. The cliff is about 200 m long with height ranging between 8 and 19 m. The notch at the cliff base is about 1 m above sea level, nearly stretching along the entire cliff toe. Detailed geo-structural and geo-mechanical surveys were performed in situ, and rock samples were tested in laboratory. The relevant physical and mechanical properties were used for determining rock mass strength parameters. A finite element approach was implemented using a two-dimensional elasto-plastic finite-element stress analysis program. The stability analysis shows that the notch causes increasing shear strains spreading from the notch end towards the top cliff. Decreasing strength reduction factors affect the cliff as the notch reaches increased depth into the rock mass, and when its depth is about 2 m the analysis results do not converge. At this stage, an uninterrupted shear plane develops along which a roughly prismatic rock block can slide and then topple

Erosion hazard assessment of the cilento coastal stretch (southern italy)

This paper deals with natural and human causes giving rise to the coastal erosion of the Cilento shoreline. It is predictable that, in 2100, along the coasts of the Mediterranean Sea a sea level rise varying between 9 and 30 cm will be attained. This increase will cause also a marked rise in the coastal erosion of beaches and rocky coasts of the studied area. The current state of knowledge about erosion processes affecting beaches and cliffs of the Cilento shoreline was shown. Finally, a hazard zonation of potential beach erosions and landslides also was proposed